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i HARVARD
Systematics of UNiversiqy,
Three Species of Woodrats
4 (Genus Neotoma) in Central
~ North America
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.. _ Elmer C. Birney
INIVERSITY OF KANSAS
AWRENCE 1973
MISCELLANEOUS
PUBLICATION
No. 58
April 13, 1973
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UNIVERSITY OF KANSAS
MusEuM OF NATURAL HISTORY
MISCELLANEOUS PUBLICATION No. 58
April 13, 1973
Systematics of ‘Three Species of
Woodrats (Genus Neotoma) in
Central North America
By
ELMER C. BIRNEY
James Ford Bell Museum of Natural History
University of Minnesota
Minneapolis, Minnesota
A dissertation submitted in partial fulfillment of the
requirements for the degree of Doctor of Philosophy,
The University of Kansas, 1970
UNIVERSITY OF KANSAS
LAWRENCE
1973
UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY
Editor: Linda Trueb
Managing Editor: William E. Duellman
MISCELLANEOUS PUBLICATION No. 58
pp. 1-173; 44 figures
Published April 13, 1973
MusEuM oF NATuRAL History
UNIVERSITY OF KANSAS
LAWRENCE, Kansas 66044
WESzAe
PRINTED BY
UNIVERSITY OF KANSAS PRINTING SERVICE
LAWRENCE, KANSAS
CONTENTS
ep E NCO) FD NO) Cry LON CDN a ee ar Bs 4
MATERIAES -AND* METHODS 2228 se Sif Let ON EERE, STs D
INGKNOWELEDGMENTS 229007 ots 2 a eae eas, AO 7
AAS CONIC TTICGHIGT BE es Eva 0d Da EFL ff Sa a ey. SULT Pee ep Ae ae 8
PUISTORICATEE ACCOUNT Seewn® Dud 27 Seve eh a, oe 8
ACCOUNTS OF SPECIES AND SUBSPECIES 2°... SS ae ee ee ee 10
Western Subspecies of Neotoma floridana RIS ei a poo Rs BS 11
1
INCOLOTRAGIIUGTOPUS: = Mies OSA 1. Ae ee ee 2
| INC OLOMMERGNOUSTIPOLAUC Smsink sk ee ae S'S)
COMPARATIVE MORPHOLOGICAL ANALYSES Ee eee 36
MMAGTERTATES ANID WiiHONGr es 22 Se 2 oo 4 8) a a ee ee F756
INGN-CEOCRAPHEGHW ARTATIONG = 0250s 28 ek ee 49
NaniatlOMunval het ACCre: ste 82.5) 5 6 ee oe eee 42,
Secondany sexual) Variation, 0-52. 2 7 ee eee ee 48
erclivacl rae Walt Oise coe ee ee . 64
Variation Resulting from Captivity ETON SE MID A Mn 56
[SEOCEAPHIC AV ARPAMION = seeeee ei Ss Se ee Se ee eee 57
Rela cemNolissanduC@Olon gees. a! 5s Ee ee ee eee Sy
@uatatives Grantalt Characters a2 = 2. . ee e 66
Bacttltnieeeesemeettere he. ae ae ee, ee eh eee ee ee 76
WnivariateAnalyses.of Mensural Characters) = ==) = eee 78
Multivariate Analyses of Mensural Characters _________-_________ 99
Multivariate Analyses of Size, Color, and Qualitative
CramaleCharactenrs) stctit! sor. sae 2S) ree eee 109
Discriminant-hunction, Analyses... eee 120
Pe MORPHOLOGICALACHARACTERS 2222.2.55 2555) 2a ee 127
ROnMmPARATIVE PAmPRODUGTION. -) 9 i)... Ae ee ee 127
BORED AR AGES OE ROL OGY yee oe 0s 144
Starchs Gelstilectrophoresis of Hemoglobins — — =.) Se 144
mnnmoecleetrophoresissor Esterases: __.____. - ) ee eee 148
SO NAV ACTIVE KAR VOL OG Vee Sas ee ee 153
SeMMARY AND: ZOOGEOGRAPHIC CONSIDERATIONS = 157
SUCCESHIONS FORVADDITIONALSRESEARCH ...____.) a ee 160
POOCEOCRAPHIC# CONENENTS Be 22a 5: =... eee ee 161
TESTU Ria) a 08 De i eee nas 166
INTRODUCTION
Two species of woodrats, Neotoma
floridana and Neotoma micropus, have
allopatric, but adjacent, distributions on
the Great Plains; the species inhabit dis-
tinctly different environments at most
localities. Because N. floridana is brown
and N. micropus is gray, the species are
readily distinguishable. The geographic
ranges of the two, as mapped by Hall
and Kelson (1959:684), were known to
abut in the central and southern Great
Plains from southeastern Colorado and
southwestern Kansas southward to the
Gulf Coast of eastern Texas; but not a
single locality of sympatry was known.
However, it had been discovered
(Dwight Spencer, pers. com.) that mem-
bers of the two species would hybridize
in the laboratory with the production of
viable offspring.
The polytypic characteristics of both
species in the zone of potential sympatry
and the existence of a geographically
isolated subspecies of Neotoma floridana
make the problem even more interest-
ing from an evolutionary point of view.
Neotoma floridana baileyi is restricted to
the region of the Niobrara River in north-
central Nebraska. Neotoma_ floridana
campestris is a large pallid subspecies
that lives in eastern Colorado, southwest-
ern Nebraska and northwestern Kansas.
Rats of this race may have been isolated
in post-Wisconsin times from presently
contiguous populations of the species to
the east (Jones, 1964:26). The eastern
parts of Kansas, Oklahoma, and northern
Texas were inhabited by a dark brown
race known as N. f. osagensis. In south-
em Texas the range of N. f. attwateri
abuts that of N. micropus; specimens of
floridana from farther east in Texas have
been referred to the subspecies rubida.
When this study was begun, Neotoma
micropus was divided into five nominal
subspecies. Neotoma micropus micropus
occupied roughly the eastern half of the
range of the species from Tamaulipas to
southern Kansas. Much of the western
part of the range reportedly was occu-
pied by N. m. canescens, allegedly a
smaller and more pallid race. Two other
subspecies, N. m. leucophea and N. m.
planiceps, were known only from their
respective type localities in New Mexico
and San Luis Potosi. The fifth recognized
subspecies, N. m. littoralis, was known
only from a few localities in southern
Tamaulipas.
Initially, this study was centered
in Nebraska, Colorado, Kansas, and
Oklahoma, an area which includes the
northern half of a zone in which the
geographic range of Neotoma floridana
approaches that of N. micropus. The
study area was selected principally be-
cause three subspecies of N. floridana
( baileyi, campestris, and osagensis) and
two of N. micropus (canescens and mi-
cropus ) occur within its boundaries. This
facilitated comparison of a variety of
parameters in order to determine rela-
tionships among these five taxa. Al-
though it had been supposed that the
ranges of N. f. campestris and N. f. osag-
ensis met in north-central Kansas, the
exact zone of contact and the nature of
the interaction had not been documented.
Moreover, N. albigula generally is con-
sidered to be closely related to both N.
floridana and N. micropus (Burt, 1960;
Hooper, 1960); this species occurs in
southeastern Colorado and the western
part of the Oklahoma panhandle. Finley
(1958) suggested that N. albigula and
N. micropus formed natural hybrids in
this region. Finally, the area was selec-
ted because of its accessibility to Law-
rence, Kansas. This facilitated both field
and laboratory investigations.
Ultimately, all available specimens of
both species from the initial region of
study and from near the zone of potential
contact in Texas were examined. All
specimens of N. micropus in the Museum
of Natural History of the University of
Kansas were included, and selected spec-
imens of N. micropus were examined in
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 5
other museums if it seemed likely that
they might reveal information on the re-
lationship of this species to N. floridana.
Eastern subspecies of N. floridana were
treated taxonomically by Schwartz and
Odum (1957); with the exception of N.
f. rubida, which occurs in extreme south-
eastern Texas, the eastern subspecies
were not considered in my investigation.
One other species, Neotoma angus-
tipalata, is considered herein. The affi-
nities of this large woodrat, known only
from Tamaulipas and San Luis Potosi,
Mexico, have remained enigmatic since
it was described by Baker (1951) as a
member of the Neotoma mexicana spe-
cies-group. Neotoma angustipalata since
has been considered by different authors
to be closely related to N. mexicana, N.
micropus or N. albigula.
Parameters studied in the field in-
cluded habitat preference and utilization,
exact distributional relationships in those
areas where members of two taxa might
come into contact, and seasonal repro-
ductive patterns of natural populations.
Parameters studied in the laboratory in-
cluded data on the following: 1) control
and experimental matings of members of
each taxon to those of each other taxon;
2) mating success and fecundity of hy-
brids; 3) growth and development of
hybrids and nonhybrids; 4) karyological
analyses; 5) serological studies involving
hemoglobin — electrophoretic patterns
(Birney and Perez, 1970) and immuno-
electrophoretic reactions of esterases; 6)
water balance physiology (Birney and
Twomey, 1970); and 7) univariate and
multivariate analyses of geographic varia-
tion of mensural and qualitative morpho-
logical characters.
The primary purposes of my research
have been to elucidate the systematic
and evolutionary relationships, assess the
zoogeographic history and _ re-evaluate
the nomenclatorial arrangement of the
woodrats studied. A secondary purpose
has been to compare so-called classical
taxonomic procedures with some of the
newer methods of systematics and
thereby evaluate the applicability of the
various methods to systematic studies of
closely related mammalian taxa.
MATERIALS AND METHODS
The general materials and methods
that pertain to several facets of the study
are discussed below. Specific materials
and methods are related in detail pre-
ceding results and discussion of the vari-
ous topics covered.
Initial efforts to collect live woodrats
for laboratory studies were undertaken
in September 1966. The last animals of
the colony were sacrificed in October
1969. Specimens studied in the labora-
tory were obtained either by dismantl-
ing active dens and capturing the rats
by hand as they fled, or by trapping them
in live-traps set near active dens. Hava-
hart traps (18 by 5 by 5 inches) were
found to be highly successful, easily
transported, and_ relatively durable.
Woodrats are not difficult to trap and
can be taken in practically any device
large enough to permit entry and con-
structed to prevent escape. In rocky
habitats, usually it was necessary to use
traps, but in other areas woodrats were
captured more often by hand. To pre-
vent undue destruction of available den-
ning sites at two localities of special in-
terest (Major County, Oklahoma, and
Cherry County, Nebraska), woodrats
were obtained only by trapping.
Animals used in laboratory experi-
ments were obtained during the months
indicated at the following localities (here
specified only to county; see lists of spec-
imens examined for exact localities of
record within these counties): NE-
BRASKA: Cherry County (March and
April 1967, August 1968); Rock County
(August 1968). COLORADO: Baca
County (April and May 1968); Prowers
County (April 1968). KANSAS: Barber
County (October 1966, March and July
1968); Douglas County (September, Oc-
tober, and November 1966, March 1967,
February and March 1968, March 1969);
Ellis County (December 1966); Ells-
worth County (September 1967, October
6 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
and December 1968); Finney County
(September and October 1968); Hamil-
ton County (September 1968); Haskell
County (September and November 1966,
June 1967, February, May, and August
1968, April 1969); Hodgeman County
(September and November 1968); Logan
County (August 1967); Meade County
(November 1966, June 1967); Ness
County (September 1968); Russell
County (December 1968); Stevens
County (August 1968). OKLAHOMA:
Dewey County (June 1968); Major
County (June 1968, January 1969).
Woodrats were housed indoors and
maintained on a daily regime of 14 hours
of light and 10 hours of darkness from
1 February to 1 October. Illumination
from several windows in the animal
rooms was the only source of light dur-
ing other months. An attempt was made
to maintain a stable temperature of 20°C
in the animal rooms, but temperatures
ranged from as low as 13°C at times dur-
ing winter to as high as 30°C on occa-
sional summer afternoons. During one
three-day period in June 1968, air con-
ditioning failed and the temperature
soared to at least 35°C and may have
surpassed 38°C. No deaths were attrib-
uted to extremes in temperature, but con-
sumption of water increased noticeably
as temperature increased. Relative hu-
midity was not measured in the animal
rooms during the summer or winter, but
was measured regularly from March to
June, 1968, when it ranged from 15 to
45 percent.
Woodrats were caged individually ex-
cept when two were placed together for
breeding or when a female was rearing
a litter. Litters were weaned at six weeks
of age. Cages used to house woodrats
were of three general types. One type
was constructed of wood and %-inch
mesh hardware cloth. Dimensions of
these cages were 30 by 18 by 18 inches
with 3.75 square feet of floor space. The
other two types of cages used were all-
metal commercially available cages with
approximately four square feet of floor
space. Both were satisfactory, but the
type having a removable pan beneath a
grated floor could be cleaned easily with-
out disturbing the occupant. Females
with unweaned litters were kept in spe-
cial large metal cages that had eight
square feet of floor space. Although
woodrats can be maintained in smaller
cages, I doubt that these would be satis-
factory for maintenance of a breeding
colony (see Wood, 1935:109). All cages
were supplied with one gallon cardboard
milk cartons or other disposable nest
boxes of equivalent size. Cages having
solid floors were covered with wood
shavings; shredded newspaper for use as
nesting material was available in all
cages. Cages were cleaned at weekly
intervals.
Purina Laboratory Chow and water
were available to woodrats in the labora-
tory on an ad libitum regime. On occa-
sion, especially in the early phases of the
study, this diet was supplemented with
lettuce leaves and whole-kernel corn;
when it became evident that supple-
mentary foods were unnecessary, this
practice was discontinued. At times in-
dividual rats would severely reduce food
intake and begin to lose weight, usually
indicating that the incisors were broken
or maloccluding; rats with such teeth
were removed from the colony. Occa-
sionally the teeth of rats that were not
feeding properly appeared to be normal;
on these occasions feeding of laboratory
chow was discontinued and the animals
were given rolled oats ad libitum for a
few days, then gradually returned to a
diet of laboratory chow. While conduct-
ing one experiment wherein it was neces-
sary to limit protein intake, the experi-
mental group was fed only corn (see
Birney and Twomey, 1970).
Diseases and ectoparasites caused lit-
tle problem in maintaining a_ thriving
woodrat colony. In the spring of 1967
several rats died after having had diar-
rhea for two to five days, losing weight,
and having an inactive, sickly appear-
ance. Several sick rats and some that
recently had died were taken to the
Veterinary Diagnostic Laboratories afhil-
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA U
iated with Kansas State University at
Manhattan, Kansas. Although the dis-
ease was never diagnosed, the necropsy
report (H. D. Anthony, pers. com.)
stated that a “hemolytic E. [scherichia]
coli was isolated from the spleen and in-
testine of one of the specimens.” Anthony
recommended immediate treatment of
drinking water with nitrofurazone, fol-
lowed by prophylactic doses every three
months. This treatment prevented
spread of the disease, and generally
cured all but the sickest rats. On two
later occasions when more than one rat
evinced signs of the affliction, the entire
colony was treated. Cages were cleaned
after each occupancy and those that had
housed sick woodrats were washed in a
dilute lysol solution before being reused.
To prevent ectoparasites from becom-
ing a problem, each woodrat was dusted
with commercial “flea powder” before
being placed in the animal house. On
three separate occasions individual wood-
rats became infested with an unidentified
species of mite; the entire colony subse-
quently was dusted and the infested
animals were dusted on two or three suc-
cessive days. Although each of the indi-
viduals survived, two females infested at
the time of parturition abandoned their
litters. Rats infested with mites tend to
be lethargic, lose weight rapidly, and
have matted, swollen eyes.
In addition to study of live animals,
a total of 2163 museum specimens, in-
cluding seven holotypes or lectotypes,
was examined by me. Several hundred
additional specimens were examined.
These include more than 300 laboratory-
reared individuals prepared as museum
specimens and deposited in The Museum
of Natural History of the University of
Kansas, specimens of eastern subspecies
of Neotoma floridana not treated herein,
specimens of other species of Neotoma
(especially N. albigula and N. mexicana)
examined for comparative purposes, and
woodrats examined incidentally while
searching for misidentified specimens of
the species studied.
ACKNOWLEDGMENTS
I thank the following agencies for
financial support for this investigation:
1) National Science Foundation Grant
GB-4446X administered by the Commit-
tee on Systematics and Evolutionary Bi-
ology at The University of Kansas, pro-
vided a Research Traineeship for my
support from September 1966 until June
1969 and additional funds for cages and
equipment to maintain woodrats in the
laboratory; 2) Travel grants for field
work and museum visitations were re-
ceived from the Graduate School and the
Museum of Natural History (Watkins
Grant) at The University of Kansas;
3) Research grants from the Kansas
Academy of Science supplied monies
used to purchase Laboratory Chow; 4)
Funds for computer time were provided
by the Computation Center of The Uni-
versity of Kansas; 5) Partial support for
July and August 1969 was made avail-
able through The University of Kansas
General Research Fund (Biomedical Di-
vision), under grant no. 3453-5038; 6)
Equipment and supplies for serological
experiments and rabbits used for prepa-
ration of antisera were purchased with
funds from the Public Health Service and
research monies of the Department of
Zoology at The University of Kansas.
I am indebted to each of the persons
listed below for permission to examine
specimens of woodrats in their charge,
which included both arrangement of
loans and provision of working space in
their respective institutions (Museum
abbreviations used in the accounts be-
yond are in parentheses): Sydney An-
derson and Richard G. Van Gelder,
American Museum of Natural History
(AMNH); William J. Voss, Fort Worth
Museum of Science and History (FWCM
—formerly Fort Worth Children’s Mu-
seum); John P. Farney, Kearney State
College (KSC); Dwight L. Spencer,
Kansas State Teachers College (KSTC);
Robert S. Hoffmann and J. Knox Jones,
Jr., Museum of Natural History of The
University of Kansas (KU); George H.
8 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
Lowery, Jr., Museum of Natural Sciences
of Louisiana State University (LSU);
Eugene D. Fleharty, Museum of the
High Plains of Fort Hays Kansas State
College (MHP); Walter W. Dalquest,
Midwestern University (MWU); Bryan
P. Glass, Oklahoma State University
(OSU); Edwin D. Michael, formerly at
Stephen F. Austin State University
(SFA); J. Keever Greer, Stovall Museum
of Science and History of the University
of Oklahoma (SM); Dilford C. Carter,
formerly with the Texas Cooperative
Wildlife Collection of Texas Agricultural
and Mechanical University (TCWC);
W. W. Newcomb, Texas Natural History
Collection of the University of Texas
(TNHC); Robert J. Baker and Robert
L. Packard of Texas Tech University
(TT); Bernardo Villa-R., Instituto de
Biologia, Universidad Nacional Auton-
oma de México (UNAM); Charles O.
Handley, Jr., and R. H. Manville, United
States National Museum, including the
Biological Surveys Collection (USNM).
Serological experiments were con-
ducted in the Charles A. Leone Labora-
tories at The University of Kansas. Per-
sons granting permission to use these
facilities or who were especially helpful
include Jay D. Gerber, Richard D.
Koehn, Charles A. Leone, Robert B.
Merritt, and Julio E. Perez. Karyological
studies were conducted in the botany
laboratories at The University of Kansas
and in the cell biology laboratories at
Texas Tech University. Raymond C.
Jackson at Kansas and Robert J. Baker at
Texas Tech were especially generous
with their supplies, equipment, and time.
James Fraine and Sievert A. Rohwer as-
sisted in the use of numerical taxonomy
programs and other analyses of data, all
TAXONOMIC TREATMENT
HISTORICAL ACCOUNT
Although woodrats were observed in
North America by early naturalists such
as John Bartram, no species was treated
taxonomically until early in the nine-
teenth century. Ord (1818:181) pub-
of which were conducted at the Compu-
tation Center of The University of
Kansas.
I am especially indebted to J. Knox
Jones, Jr., formerly of the Museum of
Natural History and Department of Sys-
tematics and Ecology of The University
of Kansas, for his excellent advice and
general assistance throughout this study
and for editorial advice in preparation
of the manuscript. Frank B. Cross and
Raymond C. Jackson also critically read
the manuscript and provided sound edi-
torial advice.
Persons deserving of special thanks
for assistance in the field include David
M. Armstrong, Russell H. Birney, Jay D.
Gerber, Thomas H. Kunz, D. Michael
Mortimer, Robert R. Patterson, Duane
A. Schlitter, Ronald W. Tumer, and
Larry C. Watkins. Additionally, D.
Michael Mortimer assisted by cleaning
woodrat cages in the summer of 1968
and Hugh H. Genoways fed and watered
the animals when it was necessary for
me to be absent.
Several of my colleagues at The Uni-
versity of Kansas, especially David M.
Armstrong, Hugh H. Genoways, Robert
S. Hoffmann, and Carleton J. Phillips,
were both stimulating and helpful by
giving needed technical advice and will-
ingly discussing topics germane to my
research. Sydney Anderson, the Ameri-
can Museum of Natural History, assisted
this study in a similar manner.
My wife, Marcia Bimey, has been
both helpful and patient throughout this
study and my graduate career. She pre-
pared most of the figures used herein,
typed drafts of the manuscript, and pro-
vided much needed clerical assistance.
lished a short description and figure of
Mus floridanus, a woodrat from eastern
Florida. Previously, Ord (1815:292)
described the bushy-tailed woodrat as
Mus cinereus. Having noted the distinc-
tive dental characters of the New World
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 9
rats, Say and Ord (1825:345) diagnosed
and named the genus Neotoma and des-
ignated Mus floridanus as the type spe-
cies. Later Baird (1855:333) named
Neotoma micropus from the type locality
of Charco Escondido, Tamaulipas (see
remarks following synonymy of N. m.
micropus ).
Baird (1858:487-490, 492-495) treated
Neotoma floridana and N. micropus as
separate species, although he repeatedly
commented on the similarities between
the two. Having only the type of micro-
pus with which to compare specimens
of floridana, Coues (1877:15) considered
micropus a synonym of floridana, a con-
clusion based primarily on his interpreta-
tion of the gray pelage of micropus as
being that of an immature animal. With
additional specimens of micropus from
Tamaulipas, southern Texas, and from
“the northwestern corner of the Indian
Territory” (now western Oklahoma), Al-
len (1891:282) recognized micropus as
a species distinct from floridana. Allen
(1891:285) applied a new subspecific
name, Neotoma micropus canescens, to
specimens from the Indian Territory pri-
marily on the basis of their pallid colora-
tion.
Woodrats from a population at Valen-
tine, Nebraska, were collected in June of
1888 by Vernon Bailey and later named
as a new species, Neotoma baileyi, by
Merriam (1894a:123). Merriam (1894b)
published a synopsis of the known mem-
bers of the genus Neotoma, including
fossil relatives, and diagnosed the sub-
family Neotominae. Allen (1894b:322)
described Neotoma campestris, the flori-
dana-like woodrat of northwestern Kan-
sas and northeastern Colorado, on the
basis of specimens from Pendennis, Kan-
sas (type locality), and Fort Lyons,
Colorado. In the same publication, Allen
(1894b:323) noted that he considered
the woodrats which he previously had
allocated to Neotoma micropus canescens
to be “inseparable from N. micropus.”
Neotoma attwateri was named on the
basis of a sample of woodrats from just
east of the Edwards Plateau, near Kerr-
ville, Texas (Mearns, 1897:721). Mearns
(1897:722) suggested that ‘it is not im-
probable [that N. attwateri, N.
baileyi, and N. campestris] . . . may
prove to be but geographic races of N.
floridana.” Prior to the turn of the cen-
tury, only one other name was applied to
the woodrats considered here. Elliot
(1899:279) assigned the name Neotoma
macropus [sic] surberi to specimens from
the vicinity of Alva, Oklahoma. Accord-
ing to Elliot, surberi differed from both
micropus and canescens in having a
longer tail and darker pelage.
Neotoma micropus littoralis, from
Altamira, Tamaulipas, and Neotoma mi-
cropus planiceps, based on a single spec-
imen from Rio Verde, San Luis Potosi,
were the last names applied (Goldman,
1905:31 and 32, respectively) to the
woodrats treated in this study prior to
the revision of the genus Neotoma by
Goldman in 1910. In the latter work,
Goldman recognized three subgenera
and 28 species. Only two species, Neo-
toma (Homodontomys) fuscipes and
Neotoma (Teonoma) cinerea, were not
considered members of the subgenus
Neotoma. Woodrats presently included
within the genus Neotoma, but which
were considered as separate genera at
that time are Neotoma (Hodomys) alleni
and Neotoma (Teanopus) phenax (see
Burt and Barkalow, 1942:296). Burt and
Barkalow also placed Homodontomys in
the synonymy of Neotoma.
Goldman (1910:14) considered N.
floridana and N. micropus to be separate
but closely related species comprising the
floridana species-group. Neotoma flori-
dana baileyi was thought to occur in
South Dakota, most of Nebraska and
Kansas, and in eastern Colorado. The
name campestris was treated as a junior
subjective synonym of baileyi. Wood-
rats of eastern Texas (except the extreme
eastern part, where the name N. f. rubida
Bangs was applied) and eastern Okla-
homa, were assigned to N. f. attwateri.
Goldman (1910:26-31) reinstated N. mi-
cropus canescens as the best name for
western populations of that species,
10 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
placed surberi in the synonymy of N. m.
micropus, and recognized both N. m.
littoralis and N. m. planiceps as distinct
subspecies.
Since Goldman’s revision, the nomen-
clature of woodrats has remained rela-
tively stable. Kellogg (1914:5) removed
campestris from the synonymy of baileyi
and recognized both as subspecies of
floridana. Goldman (1933:472) gave a
slightly paler (as compared to N. m.
canescens) population of micropus the
name Neotoma micropus leucophea.
Blair (1939a:5) described woodrats from
eastern Oklahoma, eastern Kansas, and
adjacent parts of Missouri, Arkansas, and
Texas as Neotoma floridana osagensis
(type locality in Osage County, Okla-
homa). Recognition of osagensis limited
the distribution of baileyi to the Noibrara
Valley of northern Nebraska. Burt and
Barkalow (1942:290) considered N. mi-
cropus to be intermediate between N.
floridana and N. albigula. On that basis
they created the micropus species-group
thus removing micropus from the flori-
dana group where it had been placed by
Goldman (1910:14). Neotoma floridana
and N. micropus were studied by Spen-
cer (1968), who concluded that the two
species are closely related and incom-
pletely speciated.
On the basis of two specimens from
the Sierra Madre Oriental of southern
Tamaulipas, Baker (1951:217) named
the species Neotoma angustipalata.
Hooper (1953:10) suggested that angus-
tipalata may represent no more than a
deeply pigmented population of micro-
pus, and Hall (1955:329) thought it
should be placed in the albigula species-
group.
ACCOUNTS OF SPECIES AND
SUBSPECIES
I regard the biological species con-
cept (Wilson and Brown, 1953:97-99;
Mayr, 1963, 1965, and 1969) as the best
presently available concept of the species
both for evolutionists and taxonomists,
and subscribe to Tilden’s (1961:22)
statement on the use of subspecies as
follows: “In defense of the use of the
subspecies concept, it may be mentioned
that in our present system of classifica-
tion the subspecies is the category ex-
pressly provided for the treatment of
populations less than species. That this
tool is imperfect must be admitted. But
to admit imperfection is not necessarily
to reject the tool entirely. The point of
view is held here, that the good results
outweigh the objections that have been
brought forward.” Because of the arbi-
trary nature of the subspecies, it is neces-
sary to state what “kind” of subspecies
is to be recognized. Lidicker (1962:169)
stated that “a subspecies is a relatively
homogeneous and_ genetically distinct
portion of a species which represents a
separately evolving, or recently evolved,
lineage with its own evolutionary ten-
dencies, inhabits a definite geographical
area, is usually at least partially isolated,
and may intergrade gradually, although
over a fairly narrow zone, with adjacent
subspecies.” Further, it was noted by
Lidicker (loc. cit.) that although most
such subspecies will not become species,
they are populations that have made ini-
tial steps toward species formation and
could form species under suitable isolat-
ing conditions. This interpretation fo-
cuses on the evolutionary process of spe-
ciation rather than on individual geo-
graphically variable characters. It is this
sort of subspecies that I have attempted
to recognize.
Taxonomic decisions were made after
intensive study and evaluation of the
morphological, reproductive, serological,
and karological data discussed beyond.
Accounts of species and subspecies are
presented first merely as a matter of con-
venience so that the nomenclatorial ar-
rangement proposed herein will obtain
throughout subsequent discussions.
Eight nominal taxa of woodrats, rep-
resenting three species, are treated in the
accounts that follow. The arrangement
of species and that of subspecies within
a species does not imply relationship or
degree of specialization. Instead, taxa
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 11
are arranged with respect to geographic
distribution, with more northern taxa
treated before southern ones. Each ac-
count includes a basic synonymy, which
is followed by a relatively brief section
of remarks. Remarks include comments
on type specimens if such are appropri-
ate, general comments on the variation
within and between subspecies, and
other comments that may be germane to
the taxonomic status of the taxon under
consideration. Records of occurrence fol-
low remarks and include both specimens
examined and additional records.
The total number of specimens exam-
ined is given for each taxon. This is fol-
lowed by exact localities from which the
specimens originated, the number of
specimens examined from each locality,
and the abbreviated designation for the
museum(s) in which specimens are
housed. In the account of N. m. canes-
cens, specimens from localities in the
United States are listed before those
from México. States and counties within
the United States are arranged alpha-
betically. Localities within each county
and Mexican state are arranged from
north to south. If two localities are at
the same latitude, the westernmost is
given first. Locality data of some speci-
mens examined were specific only to
county; these are listed as “unspecified”
after specific localities within the county.
In a few instances, a group of specimens
is from the same general locality with the
exact localities of capture varying only
slightly; these are totaled and listed col-
lectively as within a certain radius of a
single locality. Specimens judged to be
“hybrids” of two species (see account of
N. m. canescens) are listed with speci-
mens of the taxon that they most resem-
ble. Subspecific intergrades are included
under the subspecies to which I consider
them best assigned. Published citations
to localities from which specimens have
been collected but not examined by me
are listed under “Additional records.”
Also included in this category are reli-
able, published observations of woodrats
or their houses in areas known to be in-
habited by a single species of Neotoma.
Following records of occurrence, the
distribution and habitat of each taxon are
discussed. The latter topics are treated
in especial detail if they directly con-
cern the relationships of two species or
two subspecies. The general ranges of
all three species (floridana, micropus,
and angustipalata) are shown in figure 1.
Most locality records are plotted on re-
gional maps, but some were not plotted
to prevent undue crowding of symbols.
Unplotted localities are set in italic type
in lists of specimens examined and of
additional records. Localities specified
only to county were plotted only in the
absence of any other county record; sym-
bols for such records are square and
placed near the center of the county.
Localities of specimens bearing ques-
tionable data are not plotted, but are dis-
cussed in the account of N. m. canescens.
Eastern subspecies of Neotoma flori-
dana were reviewed by Schwartz and
Odum (1957). With the exception of
N. f. rubida, which I have treated only
in eastern Texas, these races of the spe-
cies are not considered here. Specimens
of Neotoma micropus were — studied
throughout the range of the species.
However, because New Mexico is well to
the west of the range of N. floridana and
to the north of that of N. angustipalata,
no attempt was made to examine all
specimens from that state. Specimens
from there were studied primarily to
determine the best taxonomic position of
the subspecies N. m. leucophea and to
determine if New Mexican woodrats fit
the pattern of variation of the species in
a general way. In the accounts that fol-
low, therefore, records of N. micropus
from New Mexico are not plotted on a
regional map and records from the pub-
lished literature are limited to those that
are distributionally marginal.
Western Subspecies of
Neotoma floridana
Neotoma floridana baileyi Merriam
Neotoma baileyi Merriam, 1894a:123 [Holotype
12 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
Fic. 1. Geographic distributions of Neotoma angustipalata, N. floridana, and N. micropus. Identi-
1) N. angustipalata; 2) N. f. attwateri; 3) N. f.
baileyi; 4) N. f. campestris; 5) N. f. floridana; 6) N. f. haematoreia; 7) N. f. illinoensis; 8) N. f.
magister; 9) N. f. rubida; 10) N. f. smalli; 11) N. m. canescens; 12) N. m. micropus; and 13) N.
m. planiceps. The symbol in Oklahoma denotes the single known locality of sympatric occurrence
of N. floridana and N. micropus. Distribution of eastern races of N. floridana follows Hall and Kels-
fication of species and subspecies is as follows:
son (1959:634).
—USNM 4311/5034 from Valentine, Cherry
County, Nebraska].
Neotoma floridana baileyi
Bailey, 1905:109.
Remarks.—Because of its present
geographic isolation, Neotoma floridana
baileyi assumes certain characteristics of
an “insular” subspecies. Although mem-
bers of this subspecies are distinctive in
at least minor characteristics of every
parameter studied, no results obtained in
this study indicate that baileyi has
evolved to a level warranting specific
status.
Records of occurrence.—Specimens exam-
ined (56).—NEBRASKA: Cherry County: Val-
entine, 6 (USNM); 4 mi E Valentine, 6 (KU);
6 mi E Valentine, 15 (KU); Clark’s Canyon,
near Valentine, 12 (USNM); 3 mi SSE Valen-
tine, 1 (KU); 10 mi S Cody, 5 (USNM); 22
mi SW Valentine, 3 (KU). Keya Paha County:
6 mi S, 8 mi E Springview, 1 (KU). Rock
County: 11.5 mi N, 7.5 mi W Bassett, 7 (KU).
Additional record—NEBRASKA: Brown
County: Long Pine (Jones, 1964:218).
Distribution and habitat—Selected
localities of recorded occurrence of Neo-
toma floridana baileyi are plotted in fig-
ure 2. Goldman (1910:25) reported as
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 13
this subspecies a woodrat from 18 mi
SE Rapid City, South Dakota, but Jones
(1964:217) stated that the individual re-
corded “is without question Neotoma
cinerea rupicola.” I have searched ex-
tensively for Neotoma floridana in Todd,
Mellette, and Tripp counties, South
Dakota, but found neither the woodrats
nor their distinctive dwellings. Habitat
that appeared suitable for woodrats was
extensive along and near the Little White
and Keya Paha rivers, and in the vicinity
of Okreek, South Dakota. Although no
specimens were taken in South Dakota,
it seems likely that N. f. baileyi will be
found there eventually. However, it is
conceivable that dispersal farther north-
ward is not possible even for a popula-
tion long in the process of adapting to
the inclement winters of northern Ne-
braska.
100 __
24-5B4E
Fic. 2. Selected locality records for Neotoma floridana baileyi (symbols solid above) and N. f.
campestris (symbols solid below) in Nebraska.
In Cherry, Keya Paha, and Rock
counties, Nebraska, N. f. baileyi occurs
in three more or less distinguishable
habitat types. On the Fort Niobrara
Wildlife Refuge these rats were abun-
dant in the heavily wooded floodplain
of the Niobrara River in March and
April 1967 and August 1968. Nests were
constructed in and around fallen trees,
inside hollow upright trees, at the bases
of upright trees, and in piles of brush
and treelimbs. In April, the bark and
cambium layers of woody twigs appeared
to serve as a primary source of food. Just
north of the Snake River Falls in Cherry
County (22 mi SW Valentine), three
specimens were taken from nests con-
structed in the steep, rocky, canyon walls
bordering the Snake River. In Keya
Paha County (6 mi S, 8 mi E Spring-
view) a single specimen was trapped
under a rocky ledge at the top of a deep
canyon several miles north of the Nio-
brara River; no additional nests or signs
of woodrat activity were located as a
result of searching similar ledges in the
immediate area and lower in the same
and adjacent canyons. Habitat of this
14 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
type apparently is marginal and not fre-
quently utilized.
Woodrats were common in aban-
doned and little-used buildings at a
ranch near Long Pine Creek (11.5 mi N,
7.5 mi W Bassett) in Rock County in
1968. At this locality I found no evi-
dence that “natural” nest-site types (e.g.
rock outcrops, trees, logs, brushpiles)
harbored woodrats, although these sites
probably are utilized occasionally. Near
Long Pine Creek at Long Pine, Brown
County, where this woodrat has been
reported to occur (Jones, 1964:218), I
found the habitat even more extensive
than at the locality discussed above. A
superficial search there for woodrats was
unsuccessful, but I am confident they
occur in the area and probably are locally
common along the creek from Long Pine
to the place where it empties into the
Niobrara River. I did not revisit the
locality of record 10 mi S Cody nor have
I searched for N. f. baileyi along the
Niobrara or elsewhere to the west of that
locality. To the east of the easternmost
locality of record (southwest of Spring-
view), I have searched for these wood-
rats as far as eastern Boyd and Holt
counties. Apparent marginal habitat was
found on Ponca Creek near Spencer
(Boyd County) and at several localities
along the Niobrara River. Another area
worthy of further search was observed
south of the Niobrara River just east of
Midway in Holt County. I suspect that
N. f. baileyi occurs farther to the east
than present records indicate.
Neotoma floridana campestris J. A. Allen
Neotoma campestris J. A. Allen, 1894:322
[Holotype—AMNH _ 7765/6742 from Pen-
dennis, Lane Co., Kansas].
Neotoma floridana campestris—Kellog, 1914:5.
Remarks.—Although not recognized
by Goldman (1910:24), Neotoma flori-
dana campestris is distinctly paler in
color than adjacent populations of N. f.
attwateri, occupies relatively distinct
types of habitat in comparison with other
populations of the species, and tends
generally to be larger than rats to the
east. Although relatively narrow, the
area of contact between campestris and
attwateri in eastern Ellsworth and west-
ern Russell counties, Kansas, forms an
obvious zone of integradation. The arbi-
trary line dividing the ranges of the two
taxa is drawn on a north-south axis gen-
erally corresponding to the county line
separating Ellsworth and Russell coun-
ties. A specimen (KU 119700) assigned
to campestris from only one mile west of
that county line might be equally well
assigned to attwateri, but two specimens
(KU 14001-02) from one mile east of the
line clearly are best assigned to attwateri.
The county line serves as a convenient
line of demarcation and is as accurate as
any other would be.
Records of occurrence-—Specimens exam-
ined (221)—COLORADO: Crowley County:
3 mi N Fowler, 4400 ft, 7 (KU); Olney (=
Olney Springs), 12 (USNM). El Paso County:
1.5 mi SW Fountain, 5700 ft, 2 (KU); 2.5 mi
SW Fountain, 5700 ft, 1 (KU); 3 mi S, 2 mi
W Fountain, 5600 ft, 1 (KU). Kit Carson
County: Tuttle, 2 (USNM). Yuma County:
Wray, 5 (1 USNM, 4 AMNH); 1 mi S Wray,
3550 ft, 3 (KU); 2 mi W Hale, 1 (KU); 1 mi
S, 3 mi W Hale, 1 (KU).
KANSAS: Decatur County: 5 mi S, 8 mi
W Oberlin, 1 (KU). Ellis County: 16 mi N
Hays, 13 (KU). 13 mi N; 1 mi We Haysvel
(MHP); SE % sec. 28, T. 11 S, R. 18 W (13 mi
N Hays), 6 (MHP); NW # sec. 31, T. 13 S, R.
18 W (2 mi W Hays), 3 (MHP); Hays, 7
(USNM); 0.5 mi S, 3.5 mi W Hays, 1 (KU);
2 mi S Hays, 1 (MHP); 7 mi S, 10 mi W Hays,
3 (KU); NW X sec. 11, T. 15 S, R. 20 W (8
mi S, 10 mi W Hays), 2 (MHP); SW & sec.
16, T. 15 S, R. 19 W (9 mi S, 6 mi W Hays),
1 (MHP). Finney County: 19 mi S Dighton,
it (KW): 23 mi S Dighton, 2) (KU) ys Gouve
County: Castle Rock, 9 (KU). Hodgeman
County: 4 mi S, 0.5 mi W Jetmore, 2 (KU).
Lane County: 1 mi N Pendennis, 10 (KU);
Pendennis, 29 (6 AMNH, 23 USNM); 12 mi
SW Pendennis, 2 (KU); unspecified, 2 (KU).
Logan County: NE i sec. 8, T. 13 S, R. 35 W
(2.5 mi N, 2.5 mi W Russell Springs), 1
CMMRIR RINGS, Aaa Pie Th Is) S. Jae Sie WY (UI
mi S, 1 mi W Russell Springs), 1 (MHP); 1
mi S Russell Springs, 6 (KU); 5 mi SE Elkader,
2 (KSTC); 5 mi S Elkader, 4 (KU); un-
specified, 4 (KU). Ness County: 1 mi S, 16
mi W Ness City, 4 (KU). Rawlins County:
7 mi N, 16.5 mi W Atwood, 1 (KU). Rooks
County: 1.5 mi S, 1 mi W Stockton, 6 (MHP);
3 mi S, 3 mi W Stockton, 1 (MHP); 6 mi SW
Woodston, 3 (KU); 20 mi N Hays, 1 (MHP);
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 15
SW 4% sec. 34, T. 10 S, R. 17 W (7 mi S, 4.5
mi E Plainville), 1 (MHP). Russell County:
ME msec, 34. tT. 12'S; R. 11 W (6 mi S,, 1
mi E Lucas), 1 (MHP); NW &% sec. 8, T. 13
S, R. 11 W (8 mi S, 2 mi W Lucas), 1 (MHP);
me sec, 17. T. 13)S, BR. 11 W (9 miS; 1
mi W Lucas), 4 (MHP); SE % sec. 13, T. 13
S, R. 11 W (10 mi S, 3 mi E Lucas), 1 (MHP);
0.5 mi W Russell, 1 (KSTC); NW % sec. 34,
T. 13 S, R. 12 W (11 mi E Russell), 1 (MHP);
2 mi W Wilson, 1 (KU); 6 mi S$, 4 mi E Russell,
18 (KU). Scott County: State Park, 1 (KU);
12 mi N, 3 mi W Scott City, 2 (MHP). Thomas
County: unspecified, 1 (MHP). Trego County:
sec. 29, T. 13 S, R. 25 W (Banner), 6 (KU);
unspecified, 1 (USNM). Wallace County:
Lacey Ranch (9 mi S, 4.5 mi E Wallace),
m( KU).
NEBRASKA: Dundy County: 5 mi N, 2
mi W Parks, 8 (KU); Haigler, 1 (USNM).
Additional records —COLORADO (Finley,
1958:318, unless otherwise noted): Bent
County: Fort Lyon. Elbert County: 8 mi NE
Agate; Cedar Point, 6 mi NW Limon. Fl Paso
County: 7 mi SSE Colorado Springs, 5900 ft;
10 mi S Colorado Springs; 16 mi W Wigwam
(Armstrong, 1972). Kit Carson County: South
Fork Republican River, near Flagler (Cary,
1911:114). Lincoln County: Big Sandy Creek,
near Hugo (Cary, 1911:115). Pueblo County:
N of Pinon (Warren, 1942:209); Chico Basin,
20 mi N Pueblo (ibid.); Pueblo. Yuma County:
Dry Willow Creek, Boyce Ranch.
NEBRASKA (Jones, 1964:219): Chase
County: 5 mi S Imperial. Dawson County:
10 mi S Gothenburg. Frontier County: vicinity
Curtis. Hays County: 0.5 mi S Hamlet. Lin-
coln County: North Platte; sec. 10, T. 11 N,
R. 27 W (5 mi S, 2.5 mi W Brady). Red
Willow County: McCook.
Distribution and habitat—Locality
records for Neotoma floridana campestris
are shown in figures 2, 3, and 4. Several
localities listed by Finley (1958:318)
and one reported by Jones (1964:219)
are based on observations of dens by
collectors and laymen. Of the undocu-
mented reports I have traced, I accept
the following: 5 mi S Imperial, Chase
Co., Nebraska (Jones, 1964:215); near
Flagler, Kit Carson Co., Colorado, and
near Hugo, Lincoln Co., Colorado (Cary,
1911:114, 115); Chico Basin, 20 mi N
Pueblo, Pueblo Co., Colorado, and N of
Pinon, Pueblo Co., Colorado (Warren,
1942:209). I have disregarded the follow-
ing records pending their documentation
by specimens: 6 mi N, 12 mi W Pueblo,
Pueblo Co., Colorado—this is a den rec-
ord reported by Finley (1958:318) and,
although the den most likely was con-
structed by N. f. campestris, it is con-
ceivable that both N. mexicana (disre-
garded by Finley as constructing dens
unlike the one he observed) and N.
albigula occur at this locality; 10 mi N
Arlington, Kiowa Co., Colorado—Cary
(1911:114) entered this record on the
strength of reports by “stockmen” that a
few woodrats occurred in the area,
which, if true, probably represented N.
f. campestris but could have been N.
micropus; along the Arkansas River,
south of Chivington, in Prowers Co.,
Colorado—this is another “stockmen” re-
port cited by Cary (loc. cit.), but because
micropus now is known on the north side
of the Arkansas River both east and west
of this locality, it is more likely that the
observed woodrat dens were those of
that species; Arkansas River bottom, near
Holly, Prowers Co., Colorado—originally
reported by Warren (1910:112), this rec-
ord of woodrat dens clearly should be
removed from localities included in the
distribution of campestris because micro-
pus has been collected approximately six
miles east in adjacent Kansas (Coolidge)
and the general habitat near Holly is
more like that of micropus than that of
campestris.
One other locality of record for
campestris is worthy of comment. Finley
(1958:318) discussed a specimen repre-
sented only by a skull with incomplete
data (USNM 6301) and Armstrong
(1972) reported another (USNM 6320)
of N. floridana from Denver, Colorado,
both collected by E. Palmer. Both au-
thors agree, as do I, that Denver is cer-
tainly not within the present distribu-
tional range of campestris and, although
the identity of the skulls is not in ques-
tion, they probably are from some lo-
cality(ies) to the east of Denver.
Considering only the records ac-
cepted, the distribution of campestris in
Colorado extends from just north of the
Arkansas River (Fort Lyon, 3 mi N
Fowler, and Olney Springs) to the foot-
hills of the Rockies (several localities
MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
16
.-—-
soe Ss
oo
FN
(
eee
100 Miles
Fic. 3. Selected locality records for Neotoma floridana campestris (symbols solid below) and N.
micropus canescens (solid symbols) in Colorado.
N. f.
Circles rep-
>
ri (symbols solid above), and N. micropus canescens (solid symbols) in Kansas.
resent records accompanied by specific locality data; squares denote records specific only to county.
Fic. 4. Selected locality records for Neotoma floridana campestris (symbols solid below)
attwate
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA Ly
south and southeast of Colorado Springs),
thence northeastward at least as far as
Wray and in Nebraska as far as North
Platte. In Kansas, the race occurs east
to the line (discussed above) between
Russell and Ellsworth counties, where
campestris intergrades with attwateri. I
have not attempted to determine the
northern limit of range of campestris
through field investigations, but Ander-
sen and Fleharty (1967:39) did not find
woodrats in Jewell County, Kansas, and
neither Jones (1964) nor Choate and
Genoways (1967) reported finding them
in southern Nebraska east of Red Willow
County. The first specimens to be asso-
ciated with the name campestris in Ne-
braska were reported by Jones (1954:
485), although Goldman (1910:25)
earlier listed a specimen from Haigler
under the name baileyi.
The southern extension of the species
in western Kansas seems to correlate well
with the southern extent of the Ogallala
limestone formations north of the Arkan-
sas River. I have searched for woodrats
throughout the area between the Arkan-
sas River and the southernmost locality
records for campestris. Specimens of
campestris from the Pawnee River in
northern Finney County are from only
about 20 miles north of a locality (just
north of the Arkansas River) where I
have collected Neotoma micropus. The
distributional status of floridana and mi-
cropus in those areas where the two
might come into contact is discussed in
the account of N. m. canescens.
A detailed and extensive ecological
account of N. f. campestris in Colorado
is given by Finley (1958:499-514). He
found that this rat is one of the most
versatile species of the genus in utilizing
available materials, rocks, tree cactus,
trees, or bushes for the construction of
dens. Type of vegetation available is
apparently of little importance, with the
exception that unsculptured shortgrass
prairie is insufficient for the fulfillment
of denning requirements. In Kansas and
Nebraska the situation is undoubtedly
much the same. In Dundy County, Ne-
braska, I have seen houses of campestris
constructed in sagebrush in a manner
that rendered them indistinguishable
from houses of micropus in southwestern
Kansas. At several localities in Kansas
(e.g. 19 mi S Dighton, Finney County,
and 4 mi S and 0.5 mi W Jetmore, Hodge-
man County) I have collected this wood-
rat from rock outcrops in otherwise open
grasslands. In many cases the nearest
outcrops or river systems were several
miles distant. At two localities (16 mi
N Hays, Ellis County, and 6 mi S and 4
mi E Russell, Russell County ) large pop-
ulations of campestris were observed in
eastern red cedar windbreaks not far
from major rivers (the Saline River and
the Smoky Hill River, respectively).
Most nests in the windbreaks were on
the ground at the bases of trees, partially
shielded by overhanging boughs. A few
nests, however, were two to about 10 feet
above the ground, supported solely by
the trees. Along the Pawnee River in
Finney County and the Smoky Hill River
in Logan County, woodrats were living
in piles of flood debris. In some cases the
debris served as a skeleton upon which
the rats had amassed large superstruc-
tures, but in others the only outward
signs of the presence of woodrats were
fecal droppings and faint runways.
Throughout the range of N. f. cam-
pestris, the distributional pattern is one
of apparent disjunctness, with most pop-
ulations almost certainly at least semi-
isolated. Such a pattern probably re-
sults from inability of these woodrats to
permanently occupy shortgrass prairie
between river systems, rock outcrops,
and stands of trees. A study of long-
range dispersal habits of the race would
be enlightening in revealing how iso-
lated populations are founded and how
much (if any) interpopulational gene
flow takes place (see Wiley, 1971).
Neotoma floridana attwateri Mearns
Neotoma attwateri Mearns, 1897:721 [Holotype
—USNM 11964/10402 from Lacey’s Ranch,
Turtle Creek, Kerr Co., Texas].
[Neotoma floridana] attwateri—Elliot, 1901:
ee
18 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
1939:5
Okesa,
Neotoma floridana osagensis Blair,
[Holotype—UNMZ 76070 from
Osage Co., Oklahoma].
Remarks.—Relegation of the name
Neotoma floridana osagensis to the syn-
onymy of N. f. attwateri extends the dis-
tribution of attwateri north to Kansas
and Missouri. Total geographic varia-
tion within the subspecies is increased as
a result of this change. As discussed be-
yond, the pattern of variation northward
through Texas and in southern Oklahoma
is clearly clinal, and lacking in abrupt
changes that might indicate either re-
stricted gene flow or secondary inter-
gradation. I have not examined speci-
mens from the area between Hill and
Robertson counties, Texas, but according
to Strecker (1924:16 and 1929:220)
woodrats are common in that area, at
least along the Brazos River, Tehuacana
Creek, and White Rock Creek. These
reports indicate that although docu-
mentary specimens may be lacking,
woodrats are more or less continuously
distributed throughout the area in which
the ranges of attwateri and osagensis
were alleged to meet; therefore, no rea-
son exists to suspect reduced gene flow.
The pattern of variation at the zone
of contact between attwateri and campes-
tris is discussed in the remarks of the
previous account. On the east, the range
of attwateri meets that of N. f. illinoensis
in Missouri and Arkansas and that of N.
f. rubida in southeastern Texas. I have
only superficially studied woodrats from
Missouri and Arkansas, and cannot com-
ment in detail on the relationships of
illinoensis to attwateri. These two races
seemingly resemble each other to a
greater degree than either resembles
rubida, but detailed study might not
support this supposition. I have exam-
ined specimens of rubida from Texas and
found woodrats assignable to that name
relatively distinct from those represent-
ing attwateri. One specimen from Harris
County, Texas (SFA 2312), appears to
be an intergrade between the two sub-
species, but herein is assigned to attwa-
teri on the basis of its comparatively
small size and the absence of reddish
coloration typical of rubida.
Records of occurrence.—Specimens examined
(680).—KANSAS: Allen County: 2 mi N, 0.5
mi W Neosho River Bridge, Humbolt, 2 (KU).
Anderson County: 3.7 mi S Garnett, 1 (KU);
4.5 mi NNE Welda, 1 (KU). Chase County:
9 mi E Lincolnville, 1 (KU); 1.5 mi S Safford-
ville, 1 (KSTC). Chautauqua County: Cedar
Vale, 8 (USNM); 1 mi N, 2.5 mi W Elgin,
1 (KU). Cowley County: 3.75 mi S, 1.5 mi W
Udall, 1 (KU); 6 mi N, 12 mi E Arkansas City,
29 (KU); 3 mi W Cedar Vale, 1 (KU); 86
mi E Arkansas City, 2 (KU); 3 mi SE Ar-
kansas City, 2 (KU). Crawford County: Mul-
berry, 1 (KU). Douglas County: 7 mi N
Lawrence, 1 (KU); 5 mi N, 2 mi W Law-
rence, 1 (KU); 6 mi NW Lawrence, 1 (KU);
1 mi N Midland, 2 (KU); 1 mi NW Midland,
5 (KU); 1 mi W Midland, 2 (KU); within 3
mi radius of Lawrence, 17 (KU); 1 mi N, 5
mi W Lawrence, 1 (KU); 7 mi W Lawrence,
2 (SM); 8 mi SW Lawrence, 1 (KU); 8.5 mi
SW Lawrence, 2 (KU); 10 mi SW Lawrence,
3 (KU); Lone Star Lake, 6 (KU); 9 mi S}
9 mi W Lawrence, 1 (KU); 10 mi S, 9 mi W
Lawrence, 1 (KU); 2 mi S, 2 mi W Pleasant
Grove, 1 (KU); unspecified, 1 (KU). Elk
County: 1.12 mi S, 1.75 mi W Moline, 1 (KU).
Ellsworth County: 3 mi S Wilson, 2 (KU);
3.5 mi SE Ellsworth, 8 (KU); 5 mi SW
Ellsworth, 3 (KU). Geary County: Fort Riley,
2 (USNM). Greenwood County: within 5 mi
radius of Hamilton, 32 (KU); 15 mi W Hamil-
ton, 9 (1 AMNH, 8 KU); 12 mi W Hamilton,
1 (AMNH); 4 mi S, 17 mi W Hamilton, 3
(1 AMNH, 2 KU); 4 mi S, 14 mi W Hamilton,
1 (KU); 12 mi SW Hamilton, 4 (KU); 8 mi
SW Toronto, 7 (KU); 8.5 mi SW Toronto, 17
(KU); unspecified, 1 (AMNH). Jackson
County: 6 mi S, 10 mi W Holton, 1 (KU).
Jefferson County: 13 mi NE Lawrence, 2 (KU).
Leavenworth County: 5 mi NE Lawrence, 1
(KSTC); unspecified, 10 (KU). Lyon County:
Ross Natural History Reservation, 2 (KSTC);
Emporia, 1 (KSTC); unspecified, 1 (KSTC).
Marshall County: 1 mi W Vermillion, 2 (KU).
Montgomery County: 17 mi NNE Sedan, 1
(KU). Morris County: 4.12 mi S, 6 mi W
Council Grove, 1 (KU). Rice County: 2 mi
N, 2 mi E Little River, 1 (KSTC). Riley
County: 3.25 mi S, 2 mi E Randolph, 1
(MHP); Manhattan, 9 (4 AMNH, 5 USNM).
Shawnee County: 1 mi N, 1 mi W Big Springs,
1 (KU). Wabaunsee County: 1 mi N Alma,
4 (KU). Wilson County: 2 mi N, 3 mi E
Benedict, 1 (KSTC). Woodson County: State
Lake, 2 (KSTC).
OKLAHOMA: Adair County: 5 mi SE
Flint, 1 (OSU); 3 mi NNE Chewey, 5 (SM);
7 mi W Stilwell, 1 (KU); Stilwell, 8 (USNM).
Blaine County: Canton Public Hunting Area
and Lake—vicinity of Longdale, 17 (1 FWCM,
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 19
11 OSU, 5 USNM); Salt Creek Canyon, 2
(KU); 2 mi N, 9 mi W Okeene, 1 (KSTC);
2 mi N, 2 mi W Okeene, 1 (KSTC); Roman
Nose State Park, 9 (OSU); 2 mi W Watonga,
3 (OSU). Bryan County: 10 mi SE Benning-
ton, 1 (TNHC); 5 mi N Colbert, 2 (TNHC);
0.55 mi NW Colbert, 3 (TNHC). Caddo
County: 5 mi W Cogar, 3 (SM); Fort Cobb,
2 (USNM). Canadian County: Methodist
Church Camp, sec. 18, T. 11 N, R. 10 W,
1 (SM); 5.5 mi SE Hinton, 1500 ft, 1 (KU).
Carter County: 3 mi N Springer, 3 (USNM).
Cherokee County: 2.5 mi NW Chewey, 2
(SM). Choctaw County: 1.5 mi N Hugo, 1
(OSU); 1 mi N, 3 mi E Hugo, 1 (OSU).
Cleveland County: 9 mi N, 2 mi E Norman,
2 (SM); within 5 mi radius of Norman, 18 (6
SM. 1 USNM, 11 KU); 1 mi N, 9 mi E
Norman, 1 (SM); 0.5 mi N, 6 mi E Norman,
1 (SM); 6 mi E Norman, 1 (SM); 8 mi E
Norman, 1 (SM); 9 mi E Norman, 1 (SM);
3 mi NE Noble, 1 (SM); 1 mi N, 3 mi E
Lexington, 1 (OSU); 4 mi SE Lexington, 1
(OSU); unspecified, 2 (SM). Comanche
County: Wichita Mountains Wildlife Refuge,
94 (10 OSU, 6 SM, 8 USNM); 19 mi NW
Cache, 1 (SM); Mt. Scott, 7 (USNM); 9 mi
NW Cache, 1 (SM); Chattanooga, 1 (USNM);
unspecified, 1 (SM). Cotton County: 5 mi SE
Taylor, 3 (SM). Creek County: Sapulpa, 4
(KU). Dewey County: 2 mi N, 6 mi W Long-
dale, 4 (KSTC); NE corner Canton Public
Hunting Area, 1 (OSU); 2 mi S, 2 mi W
Seiling, 1 (KU); 6 mi S, 2 mi W Seiling, 2
(KU); 5 mi W Canton, 2 (KU); 6.5 mi S,
3 mi W Seiling, 2 (KU); 7 mi S, 2.5 mi W
Seiling, 3 (KU); 8 mi S, 5 mi W Seiling, 2
(KU). Garfield County: 1 mi S, 2 mi E Enid,
1 (OSU). Haskell County: 8.5 mi S Stigler,
1 (SM). Johnston County: Tishomingo Na-
tional Wildlife Refuge, 1 (USNM). Kay
County: 1 mi S, 7 mi E Ponca City, 1 (OSU);
Ponca Agency, 1 (USNM). Latimer County:
5 mi N Wilburton, 1 (KU); 3.5 mi N Wilbur-
ton, 8 (SM); Red Oak, 1 (USNM); Wilburton,
2 (OSU). Le Flore County: 5 mi S Wister,
1 (SM); 2 mi NE Zoe, 2 (SM); 0.75 mi N
Zoe, 4 (SM). Lincoln County: 3.5 mi S
Perkins, 1 (OSU); 5 mi W Stroud, 1 (OSU).
Major County: 15 mi S Waynoka (see remarks
in account of N. m. canescens), 1 (OSU); 1.5
mi N, 0.25 mi W Cleo Springs, 8 (KSTC); 5
mi S, 2.5 mi E Cleo Springs, 2 (KSTC); 3 mi
S Chester [=1.5 mi N Seiling] (see remarks
in account of N. m. canescens), 16 (8 KSTC,
8 KU); 3 mi S, 0.5 mi E Chester, 4 (KU); 3
mi S, 1 mi E Chester, 1 (KU). Marshall
County: 6 mi N Willis, 1 (SM); 5 mi S, 1
mi W Shay, 1 (OSU); 0.5 mi E Willis, 1 (SM);
2 mi E Willis, 4 (MWU); 1 mi S, 2 mi W
Willis, 1 (SM); University of Oklahoma Biolog-
ical Station, including Engineering Tract and
Paul’s Landing, 19 (2 OSU, 17 SM); unspec-
ified, 4 (1 MWU, 2 OSU, 1 SM). Mayes
County: 1 mi S Spavinaw, 6 (KU). McCurtain
County: 2 mi N Smithville, 1 (SM); 2.5 mi
W Smithville, 3 (SM); 2 mi W Smithville, 2
(SM); Beavers Bend State Park, 4 (2 SM,
2 KU); 15 mi SE Broken Bow, 1 (SM). Mur-
ray County: Sulphur, 1 (OSU); 1.5 mi S
Dougherty, 1 (MWU); unspecified, 1 (OSU).
Muskogee County: 4 mi below [=SW] Fort
Gibson Dam, 1 (OSU); 6 mi SE Fort Gibson,
1 (OSU). Okmulgee County: 3 mi S Okmul-
gee, 1 (OSU). Osage County: 10 mi NE
Pawhuska, 1 (TNHC); Osage Hills State Park,
6 (OSU); 10 mi WSW Fairfax, 3 (SM);
McClintock Boy Scout Camp, 1 (USNM);
Heartwood Mountain, 1 (OSU). Pawnee
County: 7.5 mi N, 2.75 mi W Pawnee, 1 (KU).
Payne County: 2 mi N, 15 mi W Stillwater,
1 (OSU); 1 mi N, 9 mi W Stillwater, 2 (OSU);
vicinity of Lake Carl Blackwell, 36 (34 OSU,
2 USNM); 11 mi W Stillwater, 1 (OSU); 10
mi W Stillwater, 8 (2 OSU, 6 TT); 8 mi W
Stillwater, 1 (OSU); 5.5 mi W Stillwater, 1
(OSU); 4 mi W Stillwater, 1 (OSU); Stillwater,
1 (OSU); 2 mi E Stillwater, 1 (OSU); 4 mi
E Stillwater, 1 (OSU); 5 mi E Stillwater, 1
(OSU); 1 mi S, 3 mi W Stillwater, 2 (OSU);
4.25 mi SW Stillwater, 1 (OSU); 2.5 mi S,
0.25 mi W Stillwater, 1 (OSU); 1 mi S, 3
mi W Mehan, 1 (OSU); 10.5 mi S Stillwater,
2 (OSU); unspecified, 7 (OSU). Pittsburg
County: 4 mi NW McAlester, 1 (OSU); 2 mi
E McAlester, 1 (OSU); Savanna, 1 (USNM).
Pontotoc County: 4 mi S Ada, 1 (OSU); un-
specified, 2 (OSU). Pottawatomie County: 1
mi W Pink, 3 (SM); 7 mi SE Tecumseh, 2
(KU). Pushmataha County: 4 mi SE Clayton,
1 (SM); 1 mi S Nashoba, 4 (TNHC). Rogers
County: 0.5 mi E Chelsea, 1 (OSU). Stephens
County: unspecified, 1 (SM). Tulsa County:
8 mi W Red Fork, 2 (USNM); Red Fork, 2
(USNM); unspecified, 1 (SM). Woodward
County: unspecified (see remarks in account
of N. m. canescens), 2 (SM).
TEXAS: Brazos County: 3 mi W Bryan,
1 (TCWC); 7 mi W College Station, 1
(TCWC); within 5 mi radius of College Sta-
tion, 19 (TCWC); 7 mi SW College Station,
1 (TCWC); 10 mi SE College Station, 1
(TCWC). Collins County: 1 mi NE Wylie,
2 (MWU). Colorado County: Eagle Lake, 1
(TCWC). Cooke County: Marysville, 2
(USNM); 2 mi S Marysville, 2 (TCWC);
8 mi W Gainsville, 2 (MWU); Gainsville, 1
(USNM); unspecified, 2 (USNM). Gonzales
County: Palmetto State Park, 1 (TNHC).
Gregg County: 3.2 mi E Gladewater, 1 (TT).
Grimes County: Navasota, 3 (USNM). Harris
County: 22 mi N Houston, 1 (SFA). Hender-
son County: 2 mi NE Malakoff, 1 (SFA); 12
mi SE Athens, 1 (SFA). Hill County: 4 mi
N Blum, 2 (KU). Jack County: 7 mi SE
Jacksboro, 1 (MWU). Kaufman County: 19
mi SE Dallas, 2 (TT). Kerr County: Lacey’s
Ranch, Turtle Creek, 11 (5 AMNH, 1 TNHC,
20
5 USNM); Ingram, 9 (USNM). Lawaca
County: 3 mi W Hallettsville, 1 (TCWC);
0.5 mi W Hallettsville, 1 (TCWC); 14 mi WSW
Hallettsville, 1 (TCWC). Montague County:
2 mi W Nocona, 1 (MWU); 3 mi E Nocona,
1 (MWU); 4 mi E Stoneburg, 1 (MWU).
Navarro County: Barry, 1 (SFA). Parker
County: 8.9 mi S Aledo, 13 (FWCM). Rob-
ertson County: 2 mi W Hearne, 2 (TCWC).
Tarrant County: Lake Worth Area, 1
(FWCM); Fort Worth, 1 (FWCM); 6.5 mi
S, 4 mi W Benbrook, 2 (FWCM). Victoria
County: Victoria, 1 (USNM); unspecified, 1
(USNM). Williamson County: 3 mi N Mc-
Neil, 1 (TNHC).
Additional records:
1956): Dickinson County:
(Pl. 9). Greenwood County: 7 mi E Eureka
(Pl. 2, Fig. 2). Lyon County: 6 mi N Madison
(Pl. 3, Fig. 1). Marshall County (p. 634):
2 mi S Marysville; 5.5 mi S Beattie. Riley
County: 7 mi S Manhattan (p. 551).
OKLAHOMA (Blair, 1939b:124, unless
otherwise noted): Adair County: 5 mi S
Kansas. Bryan County: 5 mi SW Colbert (Mc-
Carley, 1952:108). Cleveland County: Noble.
McClain County: 7 mi SW Norman (Hays,
1958:235, 238). Murray County: Dougherty.
Osage County: Conway Springs; Okesa (Blair,
1939a:7); 2 mi SW Okesa. Rogers County
(Blair, 1939a:7): 3 mi W Catoosa; Garnett.
TEXAS: Cooke County (Russell, 1953:
461): 13 mi NE Gainsville; 7 mi N Gains-
ville; 4 mi NNE Myra; 4 mi NE Rosston; 3
mi NE Leo. Hunt County: 5 mi N Greenville
(Baker, 1942:343). McLennan County: vi-
cinity of Waco (Strecker, 1929:220).
Distribution and habitat.—Figures 4,
KANSAS (Rainey,
15 mi E Talmage
MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
5, and 6 show localities of occurrence of
Neotoma floridana attwateri in Kansas,
Oklahoma, and Texas, respectively. This
subspecies also is known from adjacent
parts of Missouri and Arkansas. The dis-
tribution of attwateri extends from north-
central and northeastern Kansas and cen-
tral Missouri southward through Okla-
homa, western Arkansas, and eastern
Texas to the Gulf of Mexico. In extreme
southeastern Texas it is replaced by the
larger, reddish-colored N. f. rubida.
Goldman (1910:26) listed two speci-
mens as attwateri from the Edwards
Plateau at Rocksprings, Kerr Co., Texas.
I examined two specimens (USNM
117552-53) from 7 mi S Rocksprings that
were collected in 1902; I do not doubt
that they are the same specimens studied
by Goldman. The identity of these and
other woodrats, and resultant ramifica-
tions as regards distribution of several
species will be discussed elsewhere; it is
only necessary to indicate here that both
specimens are best referred to Neotoma
albigula. Neotoma floridana, therefore,
is not known to have occurred on the
Edwards Plateau in Recent times (see
Dalquest et al., 1969:250). The south-
westernmost locality of record for the
species is Ingram, Kerr County.
mee or MILES
© 10 20 30 40
Fic. 5. Selected locality records for Neotoma floridana attwateri (symbols solid above) and N.
micropus canescens (solid symbols) in Oklahoma.
locality of sympatric occurrence of the two species; for explanation of symbols see figure 4.
The encircled symbol denotes the single known
Distributional relationships of N. f.
attwateri at the western limit of its range,
where it abuts the range of N. m. canes-
cens, will be discussed in the account of
the latter. Neotoma floridana attwateri
has not been found in Nebraska; factors
possibly limiting its range to the north
are discussed by Rainey (1956:632-637 )
and Jones (1964:218).
The literature is replete with ecolog-
ical accounts of N. f. attwateri in Kansas
and northern Oklahoma but the habits
of this rat in southern Oklahoma and
Texas are not well known. Rainey (1956:
549), in one of the better ecological
studies of the species, summarized the
habitat in eastern Kansas as_ follows:
“habitat of the woodrat in eastern Kansas
is divisible into two principal types; the
osage orange, Maclura pomifera (Raf.),
hedge-row habitat type, which is the
more widespread, and the rock outcrop
type of habitat. Stone fences, upland
woods, wooded stream-courses, shrubby
hillsides, and uninhabited buildings con-
stitute habitat types of less importance.”
Fitch and Rainey (1956) contributed
significantly to a general understanding
of the ecology of woodrats in eastern
Kansas, but found them only in the
habitats reported by Rainey (loc. cit.).
My observations of attwateri in eastern
Kansas also fit the pattern outlined by
Rainey. In Ellsworth County, this wood-
rat was trapped in two markedly differ-
ent habitats. At a locality 3.5 mi SE
Ellsworth, woodrats were living in crev-
ices and around large boulders of a
steep rocky hillside just south of the
Smoky Hill River, but 5.5 mi SW Ells-
worth I found a sparsely distributed, and
apparently small, population of wood-
rats occupying what appeared to be mar-
ginal habitat along the banks of a dry
creek. Most houses were in small piles
of flood debris, but one small, active nest
was on the ground partially concealed
by the dead stems of annual weeds in
the corner of a recently harvested milo
field. A few scattered trees near the
creek may have afforded some cover and
building materials, but no dens were
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 21
observed directly associated with the
trees:
Murphy (1952:205) concluded that
woodrats in north-central Oklahoma pre-
fer postoak-blackjack oak ravines and
fringed forest ravines. Goertz (1970:96-
98) studied attwateri in the same area
and found them in various types of
woodlands, brushy areas, riparian asso-
ciations along stream banks, and to a
lesser extent in small rock outcrops in
relatively open prairie. Spencer (1968:
38) reported collecting attwateri in a
mesquite-prickly pear cactus association
in gypsum rock outcrops near the west-
ern edge of the range in Oklahoma.
A colony of woodrats in thick wood-
land along the banks of a sandy gully in
Brazos County, Texas, was studied by
Lay and Baker (1938). Rats variously
occupied surface dens in the wooded
area, burrows and root crevices in the
gully bank, and an underground burrow
in a nearby pasture. Farther north in
Texas, Strecker (1929:220) reported at-
twateri common along rocky and wooded
river banks. Bailey (1905:110) stated
that “near Ingram, in the valley of the
Guadalupe River, a few of these wood
rats were caught in the cliffs and rocks
bordering the river valley, but they were
more common under the great heaps of
driftwood and rubbish along the river
bottoms.”
As expressed or implied by most of
the authors cited and as observed by
me, the most important factor of the
habitat of Neotoma floridana (including
this subspecies and the two previously
discussed ) is the availability of cover to-
gether with materials and structural ele-
ments for construction of dwellings.
Neotoma floridana seems to be extremely
versatile as regards food requirements
and relatively opportunistic in terms of
habitat selection so long as minimal re-
quirements for cover and nesting ma-
terials are available.
Neotoma floridana rubida Bangs
Neotoma floridana rubida Bangs, 1898:185
[ Holotype—collection of E. A. and O. Bangs
to
to
36}—
104 100
—=. Ze (eo aa S .
a ee aes ee Nae
L ee Sapha age Ara | |
ee ee
jw) a mt
32/— ee. ea —K'4--+§
ar)
el. Vaca at Relay foe
| ee! : ye hy ns = {
oe == wer.
ae a
28/-
104 100
MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
96
100 Miles
96
Fic. 6. Selected locality records for Neotoma floridana attwateri (symbols solid above),
rubida (symbols solid below), and N. micropus canescens (solid symbols )
tion of symbols see figure 4.
2872 from
Louisiana].
Gibson, Terrebonne Parish,
Remarks.—The systematic status of
Neotoma floridana rubida was not a pri-
mary concern of this study, but was con-
sidered to determine the eastern extent
of the distribution of N. f. attwateri in
southern Texas. My findings agree with
those of McCarley (1959:411), except
that specimens from Nacogdoches and
Panola counties (although herein as-
signed to rubida) are much less reddish
than specimens of rubida from farther
south in Texas and those (LSU) exam-
ined from Louisiana. This may be an
area of intergradation between N. f.
rubida and N. f. attwateri or N. f. illi-
N. f.
in Texas. For explana-
noensis (or among all three). Kelson
(1952:236) referred a specimen, pre-
viously assigned to rubida (Goldman,
1910:23), from Texarkana, Bowie
County, to N. f. illinoensis, but indicated
it resembled N. f. osagensis (= N. f.
attwateri) in certain characters. I have
not seen the specimen in question and
therefore follow Kelson. Goldman (1910:
26) assigned two specimens from
Kountze, Hardin County, to attwateri
and 22 specimens from nearby Sourlake,
Hardin County, to rubida (p. 23). That
portion of Texas was mapped by him as
within the range of rubida (p. 21). I
regard the specimens from Kountze as
rubida on geographic grounds.
Records of occurrence.—Specimens exam-
ined (25).—TEXAS: Anderson County: 5.5
mi SE Slocum, 1 (SFA). Angelina County:
Diboll, 1 (SFA). Cherokee County: 0.5 mi
N Forest, 1 (SFA); 3 mi W Forest, 1 (SFA).
Nacogdoches County: 1 mi N Nacogdoches, 2
(TT); Nacogdoches, 3 (SFA); 5 mi S Nacog-
doches, 1 (SFA); 8 mi S Nacogdoches, 1
(SFA). Panola County: 2 mi S, 5 mi W
Carthage, 1 (SFA). Polk County: 14 mi N
Camden, 4 (TCWC); 12 mi W Camden, 1
(TCWC). Trinity County: 1 mi E Trinity,
11 (TCWC). Walker County: 17 mi WNW
Huntsville, 1 (TCWC); Huntsville, 2 (TCWC);
4 mi E Huntsville, 1 (TCWC); 2 mi SW Hunts-
ville, 1 (TCWC); 6 mi S Huntsville, 1
(TCWC); 11 mi NW New Waverly, 1
|(TNHC).
Additional records: TEXAS: Hardin
County: Kountze (Goldman, 1910:26); Sour-
lake (Goldman, 1910:23).
Distribution and habitat—The dis-
tribution of N. f. rubida in Texas is shown
‘in figure 6. I have not studied woodrats
of this subspecies in the field, but Mc-
‘Carley (1959:411) indicated that their
habits are not markedly different from
those of N. f. attwateri in Texas. Davis
-(1960:192) reported that in some areas
of eastern Texas woodrats live in bur-
rows and do not construct surface nests.
If true, this would be a departure from
the usual habits of N. floridana in north-
ern and western portions of the range.
Neotoma micropus
Three nominal subspecies of Neo-
toma micropus are recognized herein;
this is a reduction by two in the number
heretofore regarded as valid. In com-
parison with most other species of wood-
rats, the biological attributes (including
geographic variation and taxonomy) of
micropus have received relatively little
attention from mammalogists. As indi-
cated previously, I studied micropus
throughout its geographic range, but less
intensively in New Mexico than in other
areas.
Recent studies have shown that
Neotoma micropus and Neotoma albigula
are more closely related than previously
was thought. The two species have been
found together at many localities and at
some of these they apparently hybridize.
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 23
Finley (1958) first reported specimens
from Colorado that appeared to be pos-
sible hybrids and Anderson (1969) re-
searched this problem in Chihuahua and
Coahuila. I have examined the material
studied by Finley as well as additional
material from Texas and New Mexico.
Elucidation of the micropus-albigula
problem eventually will affect the total
understanding of the systematics of the
woodrats of both of these species and of
Neotoma floridana. In this report, how-
ever, I have concentrated on micropus
and floridana.
The patterns of geographic variation
in micropus are such that I considered
three alternative schemes with regard to
the assignment of subspecific names. Ir-
respective of the alternatives, it seems
clear that the woodrats from White
Sands, New Mexico, are only slightly
more pallid ecomorphs of populations of
the species in adjacent areas and do not
warrant recognition at the subspecific
level. However, one of the alternatives
discussed and rejected below would re-
quire use of the name leucophea for all
populations of the species in western
Texas, New Mexico and adjacent Chi-
huahua, Coahuila, and Nuevo Leon.
The first alternative was to leave ex-
isting names (with the exception of
leucophea) unchanged and simply de-
scribe geographic variation within that
system. The only advantage seemed to
be that of nomenclatural stability. Rec-
ognition of a darker eastern subspecies
(micropus) and a generally paler western
subspecies (canescens) would obscure
some trends in variation in color and in
external and cranial sizes. This alterna-
tive also would result in continued rec-
ognition of the name N. m. littoralis,
even though woodrats previously as-
signed to that name differ appreciably
from specimens of N. m. micropus from
farther north in Tamaulipas only in be-
ing somewhat more brownish.
The second alternative involved rec-
ognition of seven subspecies to denote
each general kind of variant seen.
Neotoma micropus littoralis and N. m.
24 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
planiceps would continue to be recog-
nized. Neotoma micropus micropus
would be restricted to the small, dark,
coastal woodrats of central and northern
Tamaulipas. A new name would be pro-
posed for the large, intermediate-colored
woodrats of the Texas Coast and adjacent
inland areas. The available name N. m.
surberi would be applied to the large,
dark woodrats of south-central Kansas
and western Oklahoma (not including
the panhandle of that state). The name
canescens would be restricted to the
large, pale-colored woodrats of the Okla-
homa Panhandle, southwestern Kansas,
and southeastern Colorado; and_ the
name leucophea would be applied to the
small, pallid woodrats of New Mexico,
western Texas, and México, exclusive of
coastal Tamaulipas and the vicinity of
Rio Verde, San Luis Potosi.
The third alternative, and the one
adopted, involves provisional retention of
the name N. m. planiceps (pending ac-
quisition of specimens that elucidate the
distributional and morphological rela-
tionships of this woodrat, which pres-
ently is known only by the holotype).
The name N. m. littoralis is placed in the
synonymy of N. m. micropus, a subspe-
cies of small, dark-colored (often brown-
ish) woodrats of coastal Tamaulipas. All
other populations of the species, includ-
ing those previously known as N. m.
micropus from localities other than
coastal Tamaulipas, are referred to a
single subspecies, N. m. canescens. Be-
cause variation both in size and color is
gradually clinal throughout the distribu-
tion of canescens, no clearcut areas of
demarcation separate local populations.
However, to recognize only a_ single
taxon results in assignment of woodrats
that are quite different (especially from
the extremes of the clines) to the same
subspecies. Total geographic variation
within the subspecies N. m. canescens as
thus conceived exceeds that in any of
the other races considered in this study.
Neotoma micropus canescens J. A. Allen
Neotoma micropus canescens J. A. Allen, 1891:
285 [Lectotype—AMNH _ 3030/2350 from
North Beaver (=North Canadian River),
Indian Territory (Cimarron Co., Okla-
homa), near the boundary line between the
Indian Territory and New Mexico].
Neotoma macropus [sic] surberi Elliot, 1899:
279 [Holotype—Field Mus. Nat. Hist. 6755
from 3 mi W Alva, Oklahoma Territory
(Woods Co., Oklahoma) J.
Neotoma micropus leucophea Goldman, 1933:
472 [Holotype—USNM 251057 from White
Sands, 10 mi W Point of Sands, White Sands
National Monument, Otero Co., New
Mexico].
Remarks.—Contfusion exists concern-
ing the proper lectotype of Neotoma
micropus canescens. Although I would
have resolved this question differently, I
follow Finley (1958:310-312) in the
above synonymy to avoid belaboring a
controversial point. Considerations ger-
mane to the taxonomic status of this sub-
species are discussed above, including
nomenclatorial alternatives that might be
used to reflect patterns of geographic
variation within the samples of woodrats
here treated as N. m. canescens.
Records of occurrence-—Specimens exam-
ined (1102) —COLORADO: Baca County: 14
mi N, 4 mi E Springfield (Two Buttes Reser-
voir), 2 (KU); 5 mi S, 2 mi W Pritchett, 22
(KU); 2 mi N, 7 mi W Regnier, 4 (KU). Bent
County: 2 mi S, 2 mi E Hasty, 11 (KU). Las
Animas County: 11 mi N, 8 mi E Branson,
5600 ft, 4 (KU). Prowers County: 16 mi N,
1 mi E Springfield, 1 (KU); 1 mi N Two Buttes
Reservoir, 4350 ft, 1 (KU).
KANSAS: Barber County: 5 mi S Sun City,
1 (KU); 15 mi W Medicine Lodge, 1 (KSTC);
10 mi W Medicine Lodge, 16 (KU); 8 mi
SW Medicine Lodge, 2 (KU); 6 mi N Aetna,
1 (KU); 7 mi N, 7 mi W Kiowa, 2 (KSC);
7 mi N, 6 mi W Kiowa, 1 (KSC); 1 mi N
Aetna, 1 (KSC); 1 mi SW Aetna, 1 (KU);
3 mis Aetna. I (KU) SlosmieSeAcinawl
(KU); Marty Ranch, 5 (KU); unspecified, 2
(SM). Clark County: 7 mi S Kingsdown, 3
(KU); 11 mi S, 1 mi W Kingsdown, 3 (KU).
Comanche County: 7 mi S Coldwater, 3
(KSTC); 11.5 mi S, 16 mi E Coldwater, 6
(KU); Cave Creek, 1 (KU). Finney County:
1 mi S Pierceville, 2 (KU); 15 mi S, 4 mi W
Garden City, 1 (KU). Gray County: 2 mi
NW Ingalls, 1 (KU). Hamilton County:
Coolidge, 1 (KU); State Lake, 5 (2 MHP, 3
KU); 2.5 mi N Syracuse, 1 (KU); 1 mi N, 3
mi W Syracuse, 4 (KSTC); 1 mi S, 6 mi W
Syracuse, 1 (MHP). Haskell County: 2 mi
S, 4 mi W Satanta, 30 (KU); 3 mi S31 mi
IW. Satantay CK) 5 sanieSS) 4 mini
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 25
Satanta, 8 (KU). Kiowa County: 5 mi N
Belvidere, 31 (17 AMNH, 14 KU); Rezeau
Ranch, N of Belvidere, 1 (KU). Meade
County: 0.5 mi S, 4 mi E Fowler, 7 (KU);
11.5 mi E Meade, 2 (KU); 11 mi SW Meade,
2 (AMNH); vicinity of State Park (12-17 mi
SW Meade), 67 (21 AMNH, 3 MHP, 43 KU);
unspecified, 1 (KU). Morton County: 9 mi
N, 3 mi E Elkhart, 13 (KU); 8 mi N Elkhart,
3 (KSTC); 7 mi N, 2 mi W Elkhart, 2 (KU);
7 mi N Elkhart, 2 (MHP); unspecified, 4 (3
KU, 1 UNAM). Seward County: unspecified,
1 (KSTC). Stanton County: 1 mi N, 8 mi
W Manter, 5 (KU); 1 mi N, 7.5 mi W Manter,
29 (KU); 1 mi N, 6 mi W Manter, 2 (KU); 3
mi S, 14 mi W Johnson, 7 (MHP). Stevens
County: 4 mi E Moscow, 4 (KU).
| NEW MEXICO: Eddy County: 3.25 mi
NE Carlsbad, 2 (LSU); 24 mi E Carlsbad,
3500 ft, 1 (KU); 5 mi SW Carlsbad, 1 (KU);
2 mi NE Black River Village, 1 (KU); Carls-
bad Cavern, 1 (KU); Rattlesnake Spring, 30
mi SW Carlsbad, 1 (KU). Hidalgo County:
6 mi SSE Lordsburg, 4200 ft, 1 (KU). Luna
County: 3 mi N Deming, 4300 ft, 2 (KU).
Otero County: 13 mi W Tularosa, 1 (TNHC);
3 mi SW Alamogordo, 2 (TNHC); 3 mi S
Alamogordo, 3 (TNHC); 10 mi W Point of
Sands, White Sands National Monument, 3
(USNM). San Miguel County: 1 mi S, 2 mi
W Conchas Dam, 2 (KU). Santa Fe County:
0.5 mi NW Santa Fe Municipal Airport, 1
(KU); 1 mi W Santa Fe Municipal Airport,
1 (KU); 8 mi SW Santa Fe, 4 (KU); Santa
Fe Field Station, 1 (KU).
OKLAHOMA: Beaver County: 21 mi S
| Meade, Kansas, 1 (KU); 8 mi NE Gate, 1
(KU); 1.5 mi NE Beaver, 2 (KU); 3 mi NE
Slapout, 1 (SM). Blaine County: Canton
Reservoir (see remarks below), 1 (OSU).
Cimarron County: Regnier, 4375 ft, 1 (KU);
3 mi SE Regnier, 4350 ft, 1 (KU); 6 mi N
Kenton, 3 (OSU); 4 mi N Kenton, 1 (OSU);
1 mi S, 2 mi E Kenton, 1 (SM); 3 mi S, 2
mi E Kenton, 1 (OSU); 7.5 mi S, 10 mi W
Boise City, 3 (KU); 9 mi W Griggs, 3900 ft,
1 (KU). Greer County: Granite, 1 (OSU);
5 mi NE Reed, 1700 ft, 1 (SM); 1 mi S, 1 mi
W Reed, 1 (SM); 10 mi SE Mangrum, 1
(MWU). Harmon County: 3 mi W Reed, 6
(SM); 1 mi S, 6 mi E Vinson, 1700 ft, 9
(SM); 1 mi S, 2 mi W Madge, 1 (SM); 6.5
mi SE Vinson, 1 (SM); 13 mi N Hollis, 1
(OSU); 11 mi N Hollis, 2 (FWCM); 6 mi N,
2 mi W Hollis, 2 (OSU); 6 mi N Hollis, 13
(FWCM); 5.5 mi S Hollis, 5 (FWCM).
Harper County: Beaver River, Southern Great
Plains Experiment Range, 15 (OSU); 3.4 mi
N Fort Supply, 2 (USNM); 3 mi N Fort
Supply, 43 (USNM). Jackson County: 14 mi S
Olustree, 4 (TNHC). Kiowa County: 2 mi S
Lugert, 1 (OSU). Major County: 5.5 mi S
Waynoka, 2 (SM); 6 mi S, 3 mi E Waynoka,
1 (OSU); 16 mi NW Orienta, 1 (OSU); 1 mi
N, 7 mi W Orienta, 3 (KSTC); 16 mi W
Orienta, 8 (OSU); 5 mi W Orienta, 4 (2 SM,
2 USNM); 3 mi W Orienta, 1 (OSU); 3 mi
N, 9 mi W Fairview, 1 (OSU); 3 mi S Chester
[=1.5 mi N Seiling]—(see remarks below),
of (Se KSEE 29 KU) ea Siem San Oto) mi) aE
Chester, 2 (KU); unspecified, 2 (OSU). Roger
Mills County: 7 mi N Cheyenne, 2000 ft, 2
(SM). Texas County: 5.5 mi N Guymon, 3100
ft, 1 (SM); 4.5 mi N Guymon, 3100 ft, 3 (SM);
2 mi N Guymon, 3000 ft, 3 (SM). Tillman
County: 5.5 mi S Grandfield, 1 (SM). Woods
County: Alva, 7 (USNM); 2 mi W Edith, 6
(5 SM, 1 USNM); 4 mi S, 12 mi W Alva, 3
(KU); Waynoka Dunes, 1 (OSU); 3 mi S
Waynoka, 2 (SM); 5 mi S Waynoka, 1400 ft,
6 (SM). Woodward County: Alabaster Cav-
erns, 4 (3 OSU, 1 SM); Boiling Springs State
Park, 6 (1 KSTC, 5 SM); 2 mi NNW Wood-
ward, 1900 ft, 4 (SM); Woodward, 3 (USNM);
unspecified, 3 (SM).
TEXAS: Andrews County: 10 mi NW
Andrews, 1 (TCWC); 14 mi S Andrews, 1
(OSU). Aransas County: Aransas National
Wildlife Refuge, 3 (TCWC); 46 mi NE
Rockport, 3 (TNHC); 6 mi W Rockport, 1
(TNHC); Rockport, 1 (TNHC). Archer
County: 20 mi N Archer City, 1 (MWU); 6
mi W Holliday, 1 (MWU); within 5 mi radius
of Holliday, 4 (MWU); within 4 mi radius of
Mankins, 17 (MWU); 7 mi SW Wichita Falls,
1 (MWU); 6 mi S Wichita Falls, 1 (MWU);
11 mi SW Wichita Falls, 1 (MWU),; vicinity
of Lake Kickavoo, 9 (MWU); 1 mi W Scotland,
2 (MWU); 12 mi N Archer City, 1 (MWU);
9 mi N Archer City, 1 (MWU); 14 mi S
Holliday, 2 (MWU); 4 mi W Archer City, 1
(MWU); 4 mi S Archer City, 1 (MWU); 5
mi S Archer City, 1 (MWU); 7 mi S Archer
City, 1 (MWU); 7 mi NE Olney, 1 (MWU).
Atascosa County: 7 mi SE Lytle, 1 (TNHC);
7 mi SW Somerset, 1 (TNHC); 8 mi SW
Somerset, 1 (TNHC); 12 mi W Floresville, 1
(TNHC). Baylor County: 12 mi NW Seymour,
1 (MWU); Bomarton, 1 (MWU). Bee County:
12.5 mi N Beeville, 2 (TNHC). Bexar County:
San Antonio, 2 (TNHC); unspecified, 1 (KU).
Borden County: 16 mi W Gail, 1 (MWU).
Brewster County: 11 mi N Alpine, 1 (MWU);
2 mi W Alpine, 2 (AMNH_); 7.4 mi S Marathon,
1 (AMNH);5 miS Terlingua, 2 (KU); Tornillo
Creek, 12 mi N Government Springs, 2700 ft,
1 (AMNH); Government Springs, 3950 ft,
Chisos Mountains, 2 (AMNH); East base
Chisos Mountains, 2 (USNM); Burnham
Ranch, 3950 ft, 2 (AMNH). Callahan County:
30 mi SE Abilene, 1 (SFA). Cameron County:
10 mi E Rio Hondo, 4 (LSU); 8 mi NW Bay-
side, 1 (LSU); 2 mi W Port Isabel, 1 (TNHC);
Brownsville, 5 (2 KU, 1 TNHC, 2 USNM);
14.7 mi E Brownsville, 5 (KU). Childress
County: 18 mi N Childress, 1 (MWU); 15
mi N Childress, 1 (MWU); 5 mi N Childress,
26 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
1 (INHC); 5 mi S Childress, 1 (TNHC).
Clay County: 7 mi SE Wichita Falls, 2
(MWU); 2 mi NE Bellevue, 1 (MWU).
Cottle County: 13 mi N Paducah, 3 (TNHC).
Crane County: 20 mi NNW Crane, 1 (MWU).
Crosby County: Home Creek Canyon, 1
(AMNH); unspecified, 2 (AMNH). Culberson
County: 25 mi N Van Horn, 1 (MWU); 16 mi
E Van Horn, 5 (TCWC); 16 mi SE Van Horn,
8 (TCWC). Dawson County: 10 mi E Lamesa,
4 (TNHC); 12 mi NW Patricia, 1 (TNHC).
Dickens County: 7 mi NE Dickens, 1 (MWU);
5 mi NW Spur, 2 (MWU). Eastland County:
9 mi S Ranger, 2 (TNHC). El Paso County:
15 mi N El Paso, 2 (USNM); 10 mi N El Paso,
7 (USNM); East El Paso, 1 (USNM); near E]
Paso, 3 (USNM). Fisher County: 12 mi E
Hermleigh, 6 (TNHC). Floyd County: 6 mi
S, 2 mi W Quitaque, 1 (OSU). Foard County:
1 mi N, 12 mi E Crowell, 1 (MWU). Frio
County: 2 mi N Dilley, 1 (TNHC). Garza
County: 4 mi W Post, 1 (OSU). Goliad
County: 3.5 mi N Goliad, 2 (TCWC). Hans-
ford County: 6 mi S, 3 mi W Gruver, 1 (KU);
6 mi S, 2 mi W Gruwver, 1 (KU). Hardeman
County: 3 mi N Quanah, 1 (MWU); 3 mi SE
Lazare, 1 (MWU); 7 mi SW OQuanah, 2
CMW) 13:55 mi S (uanahy a ((MWU):.
Hartley County: Romero, 5 (AMNH). Haskell
County: 6 mi N, 11 mi E Haskell, 3 (MWU);
12 mi SW Haskell, 1 (MWU). Hemphill
County: 6 mi E Canadian, 4 (TCWC); 9 mi
NNE Miami, 1 (MWU). Hidalgo County: 4
mi WSW Hargill, 1 (LSU); 17 mi NW Edin-
burg, 3 (TNHC); Alamo, 1 (LSU); 5 mi S
Mission, 1 (LSU); 6 mi S McAllen, 7 (TNHC).
Howard County: 7 mi E Vealmoor, 2 (TNHC);
Big Spring, 1 (USNM). Hudspeth County:
Fort Hancock, 2 (1 AMNH, 1 USNM); W
slope Sierra Diablo, 1 (FWCM). Hutchinson
County: 1 mi S, 10 mi E Pringle, 2 (KU); 9
mi E Stinnett, 14 (TNHC). Jeff Davis County:
7 mi NW Toyahvale, 2 (MWU); 16 mi NE
Fort Davis, 3 (TCWC); Mouth of Madera
Canyon, 1 (TCWC). Jim Hogg County: 20
mi S Hebbronville, 9 (TNHC). Jim Wells
County: Alice, 1 (LSU). Karnes County: 2
mi SW Kenedy, 2 (TNHC). Knox County:
4 mi SE Vera, 1 (MWU); 5 mi NW Knox City,
1 (MWU). La Salle County: 2 mi S Wood-
ward, 1 (TCWC); 8 mi NE Los Angeles, 5
(TCWC); 3 mi NE Los Angeles, 1 (TCWC);
§ mi W Cotulla, 2 (TCWC); 25 mi E Cotulla,
1 (KU); 8 mi E Encinal, 3 (TCWC). Lynn
County: 2 mi W Tahoka, 1 (MWU). Martin
County: Stanton, 4 (USNM). Maverick
County: Eagle Pass, 1 (TCWC). McMullen
County: 21 mi W Three Rivers, 3 (TNHC);
20 mi W Three Rivers, 1 (TNHC); 10 mi W
Simmons, 2 (TNHC); 18 mi SE Tilden, 1
(LSU); 21 mi SW Three Rivers, 1 (TNHC).
Medina County: 7 mi N Castorville, 3 (KU).
Midland County: 9 mi S Stanton, 1 (TCWC).
Mitchell County: Colorado City, 2 (USNM).
Montague County: 5 mi S_ Ringgold, 1
(MWU); 3 mi N Stoneburg, 1 (MWU); 2 mi
N Stoneburg, 1 (MWU). Motley County: 6
mi N Flomot, 2 (MWU). Nueces County: })
1 mi S Bishop, 2 (TNHC). Palo Pinto County: |
Brazos, 1 (USNM). Presidio County: 7 mi W
Valentine, 7 (TNHC); 1.5 mi SE Buford Well,
Miller Ranch, 1 (TNHC); wnspecified, 1
(USNM). Reeves County: 20 mi S Pecos, 4
(KU). Roberts County: 6 mi N Miami, 4
(MWU). San Patricio County: 8 mi NE
Sinton, 4 (LSU). Scurry County: 4 mi SW
Synder, 1 (MWU); 20 mi NW Colorado City,
1 (USNM). Starr County: Garciaville, 2
(MWU). Taylor County: 6 mi W View, 4
(MWU). Terrell County: Lozier, 1 (USNM).
Terry County: 8 mi N Tokio, 1 (TNHC).
Throckmorton County: 18 mi SW Throckmor-
ton, 2 (TNHC); 20 mi SW Throckmorton [=
Lambshead Ranch], 2 (TNHC). Uvalde
County: Montell, 2 (KU); 3 mi N Sabinal,
2 (TNHC); 20 mi E Uvalde, 1 (TCWC).
Val Verde County: Comstock, 1 (USNM); Del
Rio, 2 (USNM). Ward County: 4 mi NW
Royalty, 3 (TNHC). Webb County: 45 mi
NW Laredo, 10 (KU); 40 mi NW Laredo, 1
(TNHC); 40 mi SW Catarina, 3 (TNHC);
15 mi NE Laredo, 1 (TNHC); Islitas, 10 mi
NNW Laredo, 3 (KU). Wichita County: 4
mi SE Electra, 2 (MWU); within 6 mi radius
of Iowa Park, 25 (MWU); within 2 mi radius
of Wichita Falls, 11 (MWU); 5 mi NNW
Wichita Falls, 1 (MWU):; 6 mi E Wichita
Falls, 1 (MWU); 1.5 mi N Oliversion Lake,
1 (MWU); 0.5 mi W Lake Wells, 1 (MWU).
Wilbarger County: 8 mi S, 2 mi W Vernon,
1 (MWU); 9 mi S Vernon, 1 (MWU); 15 mi
S Vernon, 2 (INHC); 7 mi S Harrold, 2
(MWU); unspecified, 2 (MWU). Willacy
County: 10 mi NW Raymondville, 1 (TNHC);
28 mi E Raymondville, 3 (1 KU, 2 TCWC).
Young County: 7 mi SW Graham, 1 (MWU).
Zapata County: 16 mi N San Ygnacio (=1.8
mi from Webb County line on highway 83),
3 (TNHC); 6 mi NW San Ygnacio, 1 (TCWC);
3 mi N Zapata, 1 (TNHC); 3.5 mi NE
Zapata, 2 (TNHC); 5 mi E Zapata, 6 (TNHC).
Zavala County: 29 mi S Uvalde, 4 (TNHC);
14 mi W Crystal City, 1 (KU); unspecified,
8) (CIN E(C)).
CHIHUAHUA: San Isidro, 10 mi SE
Zabagoza, 2 (KU); 7 mi W Porvenir, 1 (KU);
3.5 mi ESE Los Lamentos, 420 m, 1 (KU).
COAHUILA: 1 mi S, 9 mi W Villa Acuna,
8 (6 KU, 2 UNAM); 10 mi SE Villa Acuna,
1 (TNHC); Canon del Cochino, 3200 ft, 16
mi N, 21 mi E Piedra Blanca, 1 (KU); 11 mi
S Hacienda San Miguel, 2200 ft, 1 (KU); 15
mi N, 8 mi W Piedras Negras, 5 (KU); 2 mi
S, 11 mi E Nava, 810 ft, 4 (KU); Ciudad
Allende, 1 (TNHC); 10 mi SE Guerrero, 7
(TNHC); 29 mi N, 6 mi E Sabinas, 10 (KU); 10
mi E Hacienda La Mariposa, 3000 ft, 1 (KU);
Mariposa Ranch, 1 mi E Nacimiento, 27 mi
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 27
NE Ciudad Muzquiz, 1 (TNHC); La Gacha
[=La Concha], 1600 ft, 1 (KU); La Lajita,
Rancho de Ja Golondrina, 13 mi NE Ciudad
Muzquiz, 1 (TNHC); 10 mi N Ciudad Muz-
quiz, 2 (TNHC); 2 mi S, 3 mi E San Juan
de Sabinas, 1160 ft, 1 (KU); Sabinas, 4
wEeNHE): 1O'mi ESE Sabinas, 2 (KU); 9
mi NW Don Martin, 2 (KU); Don Martin, 800
ft, 2 (KU); Base of Don Martin Dam, 2 (KU);
8 mi N Hermanas, 1500 ft, 2 (KU); Hermanas,
1205 ft, 2 (KU); 1 mi S Hermanas, 1200 ft,
1 (KU); Cuatrociénegas, 1 (TNHC); 5 mi N,
2 mi W Monclova, 1 (KU); 0.5 mi E San
Antonio de Jaral, 4400 ft, 1 (UNAM); 3 mi
N, 5 mi W La Rosa, 3600 ft, 3 (KU).
NUEVO LEON: 15 mi N, 2 mi W Anahuac
[=Rodriguez], 1 (KU); 5 mi N, 3 mi W La
Gloria, 1 (KU); 5 mi WSW [General] Zuazua,
1 (UNAM); Rancho 14 de Mayo, 1 km E
Casa Principal, 1 (UNAM); 7 mi NW Provi-
densia, 1 (KU).
TAMAULIPAS: 4 mi SW Nuevo Laredo,
900 ft, 14 (KU); 4.5 mi S Nuevo Laredo, 1
(KU).
Additional records: COLORADO (Finley,
1958:315, unless otherwise noted): Baca
County: Monon, Bear Creek; Furnish Canyon;
Craugh Ranch, Cimarron River. Otero County:
18 mi S La Junta. Prowers County: 15 mi S
Lamar (Armstrong, 1972).
KANSAS: Barber County: Sun _ [City]
(Goldman, 1910:28). Grant County: 10 mi
S, 8 mi E Ulysses (record of unoccupied wood-
rat dwellings, see text beyond in this account).
NEW MEXICO (marginal records only):
Luna County: 8 mi E Deming (Goldman,
1910:29). Rio Arriba County: Rinconada
(Goldman, 1910:29). Valencia County: 8 mi
SE Grants ( Hooper, 1941:32).
OKLAHOMA (Blair, 1939b:125): Harper
County: 4 mi N Laverne. Woods County:
3 mi W Alva; White Horse Spring; Waynoka.
TEXAS (Goldman, 1910:28, unless other-
wise noted): Bee County: Beeville. Bexar
County: Adams. Brewster County: Alpine;
Altuda; Marathon. Cameron County: 11 mi
E Brownsville (Baker and Mascarello, 1969:
196). Clay County: Henrietta. Concho County:
unspecified. Culberson County: Kent. Dimmit
County: Blocker Ranch. Duval County: San
Diego. Ector County: 9 mi N Odessa (Baker
and Mascarello, 1969:196). Garza County:
Post (Baker and Mascarello, 1969:196). Hall
County: Newlin. Hudspeth County: Sierra
Blanca. Jeff Davis County: Valentine. Kinney
County: Fort Clark. Lamb County: 3 mi N
Fieldton. La Salle County: Cotulla. Lipscomb
County: Lipscomb. Lynn County: 2.5 mi S,
1 mi W Tahoka. Mawerick County: Moras
Creek; Pinto Creek. Nueces County: Corpus
Christi; Nueces Bay. Presidio County: 7 mi
NE Marfa, 4900 ft (Blair, 1940:32). Reeves
County: Toyah; Toyahvale. Roberts County:
Miami. San Patricio County: 7 mi NE Sinton
(Raun, 1966:2). Starr County: Roma; Rio
Grande City. Taylor County: Tebo. Terrell
County: Dryden. Tom Green County: San
Angelo. Ward County: Monohans. Webb
County: Dos Hermanos; Laredo; Santo Tomas.
Wheeler County: Mobeetie; 5.5 mi S, 2.5 mi
W Old Mobeetie (Stickel and Stickel, 1948:
292). Wilbarger County: Vernon. Winkler
County (Baker and Mascarello, 1969:196): 2
mi N Wink; 8 mi SSE Kermit.
CHIHUAHUA: Monument 15, Boundary
Line (Anderson, 1969:29).
COAHUILA (Goldman, 1910:21, 29, un-
less otherwise noted): 3 mi NW Cuatrociénegas
(Baker, 1953:253); 7 mi E Las Vacas; Sabinas;
Monclova (also see Anderson, 1969:43); Saltillo
(probably N. albigula, see Anderson, 1969:43).
NUEVO LEON (Goldman, 1910:28, unless
otherwise noted): Rodriguez; 70 mi S Nuevo
Laredo (Booth, 1957:15); Doctor Cos; 16 mi
S China; Allende (Jiménez—G., 1966:187);
Linares.
TAMAULIPAS (Goldman, 1910:28, unless
otherwise noted): Nuevo Laredo; 10 mi S
Nuevo Laredo (Booth, 1957:15); Camargo.
Distribution and habitat—Locality
records for Neotoma micropus canescens
are shown in figures 3, 4, 5, 6, and 7. On
the west, the range of this primarily
Lower Sonoran subspecies corresponds
roughly with the foothills of the Rocky
Mountain-Sierra Madre Oriental Cordil-
lera and associated extensions. The Rio
Grande and Canadian rivers have served
as corridors into the Rio Grande and
Pecos valleys of New Mexico (see Bailey,
1932:171) as far north as Rinconada and
possibly as far as the San Jose River
Valley near Grants. A single juvenile
tentatively identified as this subspecies
by Hooper (1941:32) extends the distri-
bution to the latter valley. In northern
México, N. m. canescens extends into the
lower mountainous areas in the natural
breaks between various mountain ranges
(Baker, 1956:129). In the watershed of
the Rio Salado, for example, canescens
is known to occur as far west as Cuatro-
cienegas. Distributional relationships of
N. m. canescens and the geographically
contiguous subspecies, N. m. micropus,
are discussed beyond in the account of
that subspecies.
In southeastern Colorado, southwest-
em Kansas, western Oklahoma, and east-
central Texas, the range of N. micropus
28 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
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[sex © dh bee czeeteae)
Miles
Fic. 7. Selected locality records in México for Neotoma angustipalata (symbols solid right), N.
micropus canescens (solid symbols), N. m. micropus (symbols solid above), and N. m. planiceps
(symbol solid below).
abuts that of N. floridana. Spencer (1968)
reported the single locality of known
sympatry, which is on the North Cana-
dian River in extreme southwestern Ma-
jor County, Oklahoma (Figs. 1 and 5).
The distributional relationships of the
two species along the zone of potential
abutment, with special emphasis on the
area of sympatry, is considered below
following a review of habitat types used
by N. m. canescens.
In comparison with Neotoma_ flori-
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 29
dana, N. micropus occurs in more xeric
habitats, is associated less often with
either trees or rocks, and usually occurs
in areas marked by a high incidence of
one or more species of cactus (genus
Opuntia). In western Kansas (Haskell
County), I have found canescens com-
mon in overgrazed shortgrass pastures,
especially where prickly pear cactus (O.
polyacantha) is locally abundant. In pas-
tures that also have soapweed (Yucca)
or sagebrush (Artemisia), large dens of
cactus stems and cow dung are con-
structed in and around these plants.
However, in pastures having abundant
cactus and lacking soapweed and sage-
brush, dens are built over clumps of cac-
tus, and are characterized by an exten-
sive underground system of tunnels and
usually a low superstructure of cactus
and cow dung. In this situation the
woodrat dwellings appear to be small
dome-shaped protrusions in an otherwise
gently rolling sea of buffalo grass and
cactus. On August 11, 1968, approxi-
mately 30 houses of this type were exam-
ined in a pasture 10 mi S and 8 mi E
Ulysses in Grant County. The dwellings
were in good repair, some even contained
green cactus stems and well-formed grass
nests, but none was occupied at that
time.
Farther east in Kansas_ (Barber
County ), this woodrat utilizes the crev-
ices and caves formed by gypsum out-
crops and often constructs dens around
trees and brush in wooded draws. In
such habitats the dwellings are not un-
like those of floridana; in fact, much of
the habitat in southern Barber County
seems to me more like that normally oc-
cupied by floridana than by micropus.
In Baca and Prowers counties, Colo-
rado, dens of N. m. canescens often are
constructed in tree cactus (Opuntia ar-
borescens). Finley (1958:494) reports
that tree cactus also is the most important
food plant of the species in Colorado,
but where other species of cactus and
Yucca are available, tree cactus is not
essential.
In New Mexico the habitat of this
woodrat is apparently similar to that in
Colorado. Bailey (1932:171) stated that
these rats “are abundant in open arid
valleys where cactus abounds and are
usually found associated with either cac-
tus or some of the thorny desert shrubs.
Their favorite location for a house is in
the midst of a bed of large prickly-pears
or thorny bushes... where an abundance
of cactus can be found for building ma-
terial.” Blair (1943a, 1943b) studied
canescens in the Tularosa basin near
Alamogordo, New Mexico, where it was
common in a mesquite association in
which cactus apparently was either ab-
sent or scarce.
Published reports of the habits of N.
m. canescens in Oklahoma and northern
and western Texas are scarce. Glass
(1949:29) found these rats nesting in
canyons along with N. mexicana and N.
albigula in the Black Mesa region of
extreme western Oklahoma. Blair (1939b:
125) stated that “its bulky nests of sticks,
liberally augmented by the remains of
prickly pear plants, often are built
around mesquite or other thorny shrubs.”
In Major County, Oklahoma, I have col-
lected this rat along the North Canadian
River where it comes into contact with
Neotoma floridana. This unique area is
discussed in more detail below. Blair
(1954:252) studied canescens in north-
ern Texas and adjacent Oklahoma, and
reported that “these rats show a remark-
able amount of variation in their ecolog-
ical preference . . . at some stations they
are found only on rock bluffs; at other
stations they live on the level plains and
away from rocks.” In the Davis Moun-
tains of southwestern Texas, Blair (1940:
32) collected woodrats of this subspecies
from nests constructed in the bases of
thorny shrubs in shortgrass-yucca, mes-
quite-cholla, and shortgrass-mesquite as-
sociations. In similar habitat in south-
western Texas, Blair and Miller (1949:
18) noted that in some cases old dens of
Dipodomys spectabilus were utilized. In
one of the more complete ecological
studies of Neotoma micropus, Raun
(1966) reported the species common in
30 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
a shortgrass-cactus-mesquite association
in San Patricio County, Texas. Blair
(1952:224) characterized micropus as
one of the commonest and widely dis-
tributed mammals in the southern part
of Texas.
In Coahuila, N. m. canescens has
been reported (Baker, 1956:285) to
avoid rocky areas and densely vegetated
arroyos. Houses are constructed most
commonly in prickly pear cactus. At one
locality (vicinity of Nava) rats lived in
oak thickets, and at another (La Rosa)
near houses constructed in short vegeta-
tion on desert flats.
In the summer of 1969, N. m. canes-
cens first was collected from north of the
Arkansas River in Colorado. This lo-
cality, near Hasty in Bent County, is
only about 10 miles from the nearest
locality record, (Fort Lyon) for N. flori-
dana. (The single specimen from Fort
Lyon was collected about 80 years ago
and the species probably does not occur
at that locality today.) Southeastern
Colorado, especially in the area of the
Arkansas River, is undoubtedly one of
the critical areas in which members of
the two species are likely to come into
contact. If they are in contact at this
time or should come together at some
future time, study of the two together
would be most interesting because sym-
patry of N. f. campestris and N. m.
canescens is not known now.
Neotoma micropus canescens is
known from four localities north of the
Arkansas River in western Kansas ( Fig.
4), but floridana is known from no
nearer than 20 miles to any of these
record stations. I have searched the in-
tervening areas intensively; most are
presently either cultivated or shortgrass
patsureland devoid of habitat likely to
support either species. Farther east in
Kansas, the hiatus between the ranges
of the two species widens appreciably
and in the south-central portion of that
state is roughly 80 miles in width. In the
upland areas of much of the hiatus, land
utilization is primarily for cultivation of
grain and the fields are not habitable for
woodrats. Intervening lowland areas,
however, are often at least sparsely
wooded, planted hedgerows are common
but discontinuous, and several small
tributaries of the Arkansas River extend
riparian communities into the zone. The
watershed of the Arkansas River is
heavily wooded along most of its course.
In September of 1967, I searched for
several days, walking long sections of the
Arkansas River and many likely-looking
hedgerows, but neither woodrats nor any
evience of their presence was seen. I am
not convinced that this area is devoid of
woodrats, but, if present, they are un-
common; thus, the chance of the two
species occurring together in south-cen-
tral Kansas seems negligible.
In northern Oklahoma, the haitus be-
tween the ranges of the two species nar-
rows rapidly and specimens of both spe-
cies are known from localities separated
by less than three miles along the Cimar-
ron River just west of Orienta. South
and west of Orienta on the north side of
the North Canadian River on either side
of U.S. Highway 281, micropus and
floridana occur together. This unique
area of sympatry was reported by Spen-
cer (1968) and subsequently was visited
by me in June, 1968, and January, 1969.
Specimens from this area in the collec-
tion at Kansas State Teachers College
(collected by Spencer) are labeled 1.5
mi N Seiling, in Major Co., Oklahoma,
whereas those collected by me (all KU)
are labeled 3 mi S Chester, Major Co.,
Oklahoma.
West of highway 281, woodrats occur
in two distinct areas. Immediately ad-
jacent to the river, vegetation is dense
and shrubby with occasional trees and
fallen trees in an area varying in width
from 30 to 80 feet. Superficially this ap-
pears to be habitat typical of floridana.
A cultivated field approximately an
eighth to a quarter of a mile in width
separates the river-edge habitat from an
area roughly an eighth of a mile wide
where yucca, cactus, sparse grass, and
scattered large trees grow on semi-stabi-
lized sand dunes. This area is super-
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 31
ficially like that often inhabited by mi-
cropus. East of the highway, the river
edge (50 to 100 feet wide) was densely
wooded in 1968 with a dense layer of
leaf-litter and a canopy that permitted
little ground vegetation. Woodrats were
not found in this habitat. Bordering the
dense trees to the south was a pasture of
relatively stable, vegetated sand dunes.
Small stands of large trees were scattered
throughout the pasture, primarily at the
bases of the dunes. Vegetation on the
sides and tops of the dunes consisted of
grass and cactus. The area extended ap-
proximately three-eighths of a mile north
and half a mile east. Farther to the east,
the density and sizes of trees increased,
density of cactus decreased, and the area
became more typical of the habitat of
floridana. In 1969, the dense woods bor-
dering the river east of the highway were
uprooted and piled in a huge windrow
bordering the sand dunes on the south.
At that time the windrow already har-
bored several woodrat dens.
Of eighteen woodrats collected at this
locality in 1965 and 1966 by Spencer
(1968), six were identified as N. flori-
dana, three as N. micropus, and nine as
probable hybrids or intergrades. I have
examined 16 of these specimens and
identified seven as floridana, three as mi-
cropus, and six as being of mixed parent-
age. Using my identifications, six flori-
dana, one micropus, and four “hybrids”
were collected east of the highway and
one floridana, two micropus, and two
“hybrids” were obtained west of the high-
way. Four of seven animals trapped west
of the highway in 1968 were identified as
micropus and three were considered to
be of mixed parentage; of 16 specimens
taken at that time from the east side, six
were identified as micropus, three as
floridana, and seven as “hybrids.” No
traps were set west of the highway in
1969, but traps set within half a mile
east of the highway yielded four mi-
cropus and eight “hybrids.” No wood-
rats identified as N. floridana were taken
from the place defined by Spencer
(1968) as the area of sympatry. How-
ever, another series of traps set in an
area 100 to 200 yards farther east caught
one floridana, one micropus, and four
“hybrids.” Although these findings are
inconclusive, it appears that the hybrid
zone may have shifted eastward at least
a quarter of a mile between 1965 and
1969, although remaining about three
fourths of a mile in length. The destruc-
tion of trees and formation of the wind-
row may have significantly altered the
ecological balance of the two species in
the area of sympatry; if so, the alteration
likely will favor N. floridana. A single
specimen trapped one mile east of the
highway in 1968 was clearly referable to
floridana; it showed no characteristics of
micropus or of hybrids.
Four specimens from Major and
Woodward counties are worthy of spe-
cial comment with respect to the dis-
tributional relationship of the two spe-
cies) athe (first COSUR3S89I) )riseauskim
and skull that is referable to floridana
on the bases of pelage (color) and
cranial characters. This specimen bears
the following information on the data
label: “15 miles south of Waynoka, Okla.,
southside of Cimmarron [sic] River, Ma-
jor Co.” Fifteen miles south of Waynoka is
no closer than nine miles to the Cimarron
River and all other specimens examined
by me from within 15 miles of Waynoka,
in any direction, are N. micropus. Be-
cause these two species hybridize at the
one known locality of sympatry, and be-
cause the locality in question here clearly
is in error as stated above, I have not
plotted this specimen on figure 5; I sus-
pect it is from some locality east of
Waynoka. Another specimen, OSU 4063,
also is not plotted because of probable
error in locality data; a skin alone, it is
from “Canton Res. Blaine Co., Okla.”
Canton Reservoir is approximately 15
miles east along the North Canadian
River from the locality of sympatry and
hybridization. This rat is gray in color
like micropus, but slightly atypical in be-
ing buffy on the shoulders and sides.
However, the color variation is so slight
that if this specimen was not otherwise
(oy)
bo
in question, it readily would be identified
as micropus. I have examined several
specimens from near the Canton Reser-
voir and all seem to be typical representa-
tives of floridana. Three explanations
seem possible: (1) both species occur
at this locality, but floridana is commoner
than micropus; (2) this is a hybrid pop-
ulation most like floridana, but occa-
sional genetic combinations result in in-
dividuals colored as in micropus; (3)
the locality data are incorrect and the
specimen is from some more western
locality. I regard the last alternative as
the most plausible and the first as the
least plausible. Both specimens appar-
ently were collected by beginning stu-
dents (field catalog numbers of both are
below 10). OSU 3891 bears a collection
date of 26 October 1958 and OSU 4063
is dated 28 October 1958. Although not
prepared by the same student, it is pos-
sible that the labels were somehow
switched in preparation. The other two
noteworthy specimens are SM 4980 and
4981, preserved only as skins. Both spec-
imens clearly were prepared some years
ago (date of collection not on specimen
labels) and are typical dark brown rep-
resentatives of floridana. The specimen
labels read “Woodward Co., Oklahoma.”
The southeastern corner of Woodward
County is two miles west of the area of
sympatry and all other specimens exam-
ined from that county are micropus. If
the zone of contact is shifting gradually
eastward and has been doing so for many
years, it is possible that floridana may
have occurred in Woodward County in
the not too distant past. It also is pos-
sible that these specimens were not from
the North Canadian River, but are from
some locality elsewhere in Woodward
County that once supported or still sup-
ports a population of N. floridana.
Farther south in Oklahoma, speci-
mens of the two species are known from
localities at a minimum of 20 miles from
each other. The Red River, 5.5 mi S
Grandfield, Tillman, Co., Oklahoma, is
the locality of capture for SM 3602, a
N. m. canescens. This locality is nearly
MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
straight south of Chattagnooga, Coman-
che County, where N. f. attwateri has
been taken. It is west along the Red
River from another floridana locality, 5
mi SE Taylor, Cotton County. South of
Taylor, in adjacent Clay and Wichita
counties, Texas, micropus is known from
several localities.
Dalquest (1968:19) stated that “the
ranges of N. floridana and N. micropus
meet in Clay and Montague counties
[Texas] but the two species do not inter-
breed.” In actuality, floridana is not
known from Clay County and micropus
is known only from the extreme western
edge of Montague County. Neotoma
micropus canescens has been collected 2
mi N Stoneburg and N. f. attwateri is
known from a locality 4 mi E Stoneburg,
a distance of 4.47 miles. Continued field
work in northern Texas and along the
Red River likely will result in the loca-
tion of a zone of contact between the
two species, but none presently is known
in northern Texas.
A specimen of attwateri (MWU
5256) obtained 7 mi SE Jacksboro, Jack
County, is from west of known micropus
localities both to the north and to the
south, but N. m. canescens has not been
taken at any nearby localities. Another
area in Texas that would be worthy of
additional field work is along the Brazos
River in Parker and Hood counties.
Neotoma micropus canescens is known
from the Brazos River just west of Parker
County in Palo Pinto County. A series
of 13 N. f. attwateri from 8.9 mi S Aledo,
Parker County, is suspiciously grayish-
brown in color, but cranially members
of the series are more or less typical of
floridana. Possibly this population con-
tains some introgressed genetic material
derived from micropus, but more likely
the color is the result of adaptation to
the local environment on the western
edge of the range of the species.
There are few records of museum
specimens of woodrats from the central
portion of Texas. Strecker (1929:220)
reported N. f. attwateri from near Waco.
West of Waco, the nearest locality of
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 33
record for N. m. canescens is approxi-
mately 175 miles distant in Concho
County. On a north-south axis there is
an apparent hiatus of some 200 miles in
the distribution of micropus along the
eastern edge of the range of the species
in central Texas. The Colorado River
and many smaller waterways traverse
this area. Insofar as I am aware, there
are no physiographic factors that would
be expected to prevent woodrats from
inhabiting this sizable portion of central
Texas, which is surrounded by areas
known to support floridana on the east
and micropus on the north, west, and
south.
Museum specimens indicate that the
two species are in close proximity in
southeastern Texas adjacent to the Gulf
Coast. However, no localities of sym-
patry are known; the nearest localities
are in Victoria County (N. f. attwateri)
and Goliad County (N. m. canescens).
Neotoma micropus micropus Baird
Neotoma micropus Baird, 1855:333 [Lectotype
—USNM 1676/554 from Charco Escondido,
Tamaulipas].
Neotoma micropus littoralis Goldman, 1905:31
[Holotype—USNM 92952 from Altamira,
Tamaulipas].
Remarks.—When Baird named Neo-
toma micropus he had specimens from
both Charco Escondido, Tamaulipas, and
Santa Rosalia (=Ciudad Camargo ), Chi-
huahua. Unfortunately no holotype was
designated by Baird. Merriam (1894b:
244) pointed out that the specimen from
Santa Rosalia is “somewhat aberrant”
and that because “the original descrip-
tion is based wholly on the Charco Es-
condido specimen . . . [it] must be taken
as the type of this species.” The speci-
men from Santa Rosalia, not seen by me,
is assignable on geographic grounds to
Neotoma albigula (see Anderson, 1969),
but Merriam’s designation of the Charco
Escondido specimen as a lectotype firmly
reserved the name for the woodrats to
which it is applied.
The decision to consider the name N.
m. littoralis as a junior synonym of N.
m. micropus was not an easy one. How-
ever, when analyzed by both univariate
and multivariate statistics, the samples of
woodrats from northern and_ southern
Tamaulipas are consistently more alike
than either is to any other sample of the
species. From north to south in Tamauli-
pas, these rats tend to become less gray-
ish and more brownish. One extreme in
this trend is reached in southern Tamau-
lipas to the south of the Sierra de Tamau-
lipas; it is the woodrats at this end of the
range that formerly were recognized as
littoralis. Alvarez (1963) studied mi-
cropus in Tamaulipas and chose to rec-
ognize two subspecies within the state.
He (p. 453) concluded that micropus
and littoralis intergraded in the vicinity
of Soto la Marina, and assigned speci-
mens from that locality to N. m. micropus
and those from localities farther south in
Tamaulipas to N. m. littoralis.
Woodrats throughout the coastal
plain of Tamaulipas have relatively
longer tails than specimens of micropus
from other localities and tend to be some-
what brownish in coloration (rather than
grayish), especially on the hind legs
where the dorsal coloration meets the
“white” of the feet. Although specimens
of micropus from southern Texas are ap-
preciably larger than those from Tamau-
lipas and are assignable to N. m. canes-
cens, an occasional specimen from the
general area of Brownsville resembles
N.m. micropus.
Woodrats from just south of the Rio
Grande near Nuevo Laredo, Tamaulipas,
are somewhat intermediate between mi-
cropus and canescens but have been as-
signed to the latter. Conversely, speci-
mens from Matamoros, Tamaulipas, have
some characteristics of woodrats from
farther north and west, but I have in-
cluded these with N. m. micropus.
Specimens from the type locality of
N. m. micropus, Charco Escondido, prob-
ably are intergrades between the small,
brownish, long-tailed coastal woodrats
and the equally small, but grayish short-
tailed woodrats in Nuevo Leon and
Coahuila. It is always somewhat incon-
34 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
venient when specimens from a type
locality appear to be intergrades. To
consider specimens from Charco Escon-
dido to be of the same subspecies as
those from Nuevo Leén and Coahuila
would result in all the woodrats herein
referred to as N. m. canescens being ar-
ranged as N. m. micropus, and those from
coastal Tamaulipas being regarded as N.
m. littoralis. Although specimens from
Charco Escondido and adjacent localities
in northwestern Tamaulipas could be
placed about equally well with either the
coastal population or with the inland and
northern populations, I concluded that
they best represent those nearer the
coast. Specimens from Tamaulipas north
to approximately Reynosa and south to
the vicinities of Ciudad Victoria (on the
southwest) and Altamira (on the coast)
are here assigned to the subspecies N.
m. micropus, with the type locality being
Charco Escondido, Tamaulipas; the
name N. m. littoralis thus becomes a sub-
jective junior synonym of N. m. micropus.
Records of occurrence.—Specimens exam-
ined (66).—TAMAULIPAS: 3 mi SE Reynosa,
1 (KU); 3 mi S Matamoros, 2 (KU); Charco
Escondido, 2 (1 UNAM, 1 USNM); 33 mi S
Washington Beach, 1 (KU); San Fernando,
180 ft, 3 (KU); 7 km S, 2 km W San Fer-
nando, 2 (KU); 12 mi NW San Carlos, 1300
ft, 4 (KU); 9.5 mi SW Padilla, 800 ft, 3 (KU);
3 mi NE Guemes, 1 (KU); 3 mi N Soto la
Marina, 3 (KU); Soto la Marina, 500 ft, 13
(12 KU, 1 LSU); 4 mi N La Pesca, 3 (KU); -
La Pesca, 2 (KU); 1 mi E La Pesca, 1 (KU);
7 mi NE Ciudad Victoria, 1 (KU); Ciudad
Victoria, 6 (KU); Sierra de Tamaulipas, 2
mi S, 10 mi W Piedra, 1200 ft, 6 (KU);
Manuel, 1 (AMNH); 6 mi W Altamira, 8
(KU); Altamira, 100 ft, 5 (USNM).
Additional records: TAMAULIPAS (Gold-
man, 1910:28, unless otherwise noted): Mata-
moros; Bagdad; 40 mi S Matamoros (Hooper,
1953:9); Sierra San Carlos [=E] Malato,
Tamaulipeca] (Dice, 1937:254); 16 km N
Ciudad Victoria (Hsu and Benirschke, 1968);
Forlén.
Distribution and habitat—The dis-
tribution of N. m. micropus is essentially
the coastal plain of Tamaulipas, extend-
ing north to the Rio Grande River and
south to Altamira, Tamaulipas (Fig. 7).
Possibly the subspecies occurs in north-
ern coastal Veracruz, but specimens from
that state are not presently available (see
Hall and Dalquest. 1963). Distributional
relationships of N. m. micropus and N.
m. canescens in western Tamaulipas,
eastern Nuevo Leén, and across the
lower Rio Grande are discussed in re-
marks above.
With respect to ecological habits, N.
m. micropus probably differs little from
N. m. canescens. According to Alvarez
(1963:453), the subspecies occurs
throughout the Tamaulipas Biotic Proy-
ince and is most common in brushy areas.
Specimens have been obtained from the
beach near La Pesca and in rocky areas
on the Sierra de Tamaulipas.
Neotoma micropus planiceps Goldman
Neotoma micropus planiceps Goldman, 1905:32
[Holotype—USNM 82105 from Rio Verde,
San Luis Potosi].
Remarks.—Dalquest (1953:158) re-
ported that no specimens of this woodrat
were collected during his investigation
of the mammals of San Luis Potosi, but
did not indicate if specimens were sought
near Rio Verde. He suggested (loc. cit.)
that the holotype of N. m. planiceps
might be “an aberrant specimen, not
fully adult, of Neotoma albigula leu-
codon.” I have examined the holotype
and concur that it is not fully adult but
concluded unequivocally that it is not a
Neotoma albigula. 1 think it possible
that Neotoma angustipalata, discussed in
the following account, may be the same
taxon as N. m. planiceps; however, spec-
imens are not presently available to re-
solve this problem.
Record of occurrence.—Specimen examined
(1)—SAN LUIS POTOSI: Rio Verde, 1
(USNM).
Distribution and habitat.——This sub-
species is known only from the type lo-
cality, which is shown in figure 7.
Goldman (1905:32) did not contribute
ecological comments in the original de-
scription of N. m. planiceps, but presum-
ably it is an inhabitant of the plains im-
mediately west of the Sierra Madre
Oriental.
|
Neotoma angustipalata
Neotoma angustipalata is one of the
least well-known members of the genus.
The species was described in 1951, long
after most species of Neotoma were at
least moderately well studied. The dis-
tributional relationship of N. angusti-
palata and N. micropus might appear to
be that of two subspecies; Hooper (1953)
and Alvarez (1963) both suggested that
angustipalata is probably no more than
_a subspecies of micropus. However, re-
sults of analyses presented beyond indi-
cate that angustipalata is best regarded
as a distinct species, albeit in the same
_ species-group as floridana and micropus.
Neotoma angustiplata Baker
_Neotoma angustipalata Baker, 1951:217 [Holo-
j
type—KU 36976 from 70 km (by highway)
S Ciudad Victoria and 6 km W of the (Pan-
American) highway (at El Carrizo),
Tamaulipas].
Remarks.—As pointed out previously,
the systematic affinities of this woodrat
_ are poorly known. They have been con-
sidered to be with Neotoma mexicana
(Baker, 1951:217), N. albigula (Hall,
| 1955:329), and N. micropus (Hooper,
1953:10; Alvarez, 1963:453). I suggested
in the previous account that N. angusti-
palata may be identical to the rat that
bears the name N. micropus planiceps.
_ Had I synonymized the two, the name
_ angustipalata would have been placed as
a junior synonym of planiceps, and the
latter would have been elevated to spec-
ific status.
I agree with Hooper and Alvarez that
N. angustipalata is much like N. mi-
cropus, but have found that it shares a
nearly equal number of characters with
N. floridana in addition to having some
characters unique unto itself. These char-
acteristics are treated in detail in the
_ discussion of quantitative and qualitative
morphological comparisons beyond.
The three specimens from San Luis
Potosi to which Dalquest (1951:363)
gave the name WNeotoma_ ferruginea
griseoventer (placed in the species mexi-
cana by Hall, 1955:330) were examined
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 35
to determine if this woodrat and N.
angustipalata also might represent the
same taxon. The type locality of N.
mexicana griseoventer is Xilitla, San Luis
Potosi; two of the specimens (LSU 3193,
3194) are from the type locality and one
(LSU 3191) is from El Salto, San Luis
Potosi. The two specimens from Xilitla
appear to be referable to N. mexicana,
but LSU 3191 is indistinguishable from
N. angustipalata and is best assigned to
that species. The similarities between N.
angustipalata and N. m. griseoventer are
many and the two may yet prove to be
synonymous. However, in all specimens
of N. angustipalata (including LSU
3191), the vomer is solid beyond the
leading edge of the palate, whereas all
N. mexicana examined by me have a
deep notch in the vomer anterior and
dorsal to the palate; the vomers of the
two specimens from Xilitla are distinctly
notched. Specimens of both species have
a deep anteroreentrant angle on MI, the
character long used to distinguish N.
mexicana from other species of Neotoma,
but several authors have commented on
the variability in depth of this angle both
in N. mexicana and N. micropus (see
especially Hooper, 1953:10).
Records of occurrence.—Specimens exam-
ined (12)—TAMAULIPAS: 70 km [by high-
way] S Ciudad Victoria, 6 km W [Pan-Ameri-
can] highway [at El Carrizo], 2 (KU); 10 km
N, 8 km W El Encino, 400 ft, 1 (KU); 12 km
S Ciudad Mante, 1 (UNAM); 2 km S Quintero,
250 m, 2 (UNAM); 4 km SSE Quintero, 2
(UNAM). SAN LUIS POTOSI: El Salto, 1
(LSU); 5 mi W El Naranjo, 1 (TT); 30 km
W Valles, edge of plateau, 1 (MWU).
Additional records——TAMAULIPAS: Ran-
cho del Cielo, 1050 m [6 km NW Gomez
Farias] (Hooper, 1953:9; Goodwin, 1954:14;
Koopman and Martin, 1959:7); Infernillo (=
Inferno), 1320 m [7 km W Gomez Farias]
(Koopman and Martin, 1959:6); Paraiso, 420
m [13 km SW Gomez Farias] (ibid.); El Pachon
(Hooper, loc. cit.; Goodwin, loc. cit.).
Distribution and habitat—Booth
(1957:15) first reported Neotoma an-
gustiplata from San Luis Potosi; reas-
signment of a specimen previously as-
signed to the species N. mexicana (see
remarks) and assignment of TT 9769
36 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
and MWU 3055 to this species further
elucidate the known geographic range
of angustiplata in the state.
All locality records for N. angustiplata
are either in or near the eastern slopes of
the Sierra Madre Oriental (Fig. 7).
Koopman and Miller (1959:2-3) de-
scribed the localities from whence their
material (owl pellets) probably origi-
nated as Tropical Evergreen Forest and
Cloud Forest. Goodwin (1954:2) de-
scribed Rancho del Cielo as being “on
the first ridge of the Sierra Madre Orien-
tal at 1150 meters. Humid, oak and
sweet gum, cloud forest (humid upper
tropical life zone) surrounding the ranch
has been thoroughly lumbered since
1952.” The specimens on which the name
originally was based were trapped “in
rocks and crevices at the base of a small
hill in thick vegetation growing in deep
humus” (Baker, 1951:218). All speci-
mens reported by Hooper (1953:9) were
collected in limestone caves.
COMPARATIVE MORPHOLOGICAL ANALYSES
In view of the ubiquity of woodrats
in the United States and México, it is
interesting that relatively little attention
has been devoted to generic variation in
Neotoma as compared with that given
other cricetine genera such as Peromyscus
(King, 1968). Hooper (1938 and 1940)
studied geographic variation in N.
fuscipes and N. cinerea. Hoffmeister and
de la Torre (1960) assessed variation in
N. stephensi, comparing it to N. lepida.
The systematics of N. goldmani were
considered by Rainey and Baker (1955).
Size and physiological attributes of sev-
eral species of Neotoma (not including
N. floridana or N. micropus) were cor-
related with selected environmental fac-
tors by Brown and Lee (1969).
Geographic variation in six eastern
subspecies of Neotoma floridana was
studied by Schwartz and Odum (1957),
but it has not been assessed in western
races of the species or in N. micropus.
Cockrum (1952:188) shifted the sub-
species boundary between N. m. mi-
cropus (herein restricted to coastal
Tamaulipas) and N. m. canescens east-
ward in Kansas from that proposed by
Goldman (1910:27), but Cockrum did
not study patterns of variation in mi-
cropus outside of Kansas. Baker (1956:
286) regarded all specimens of the spe-
cies from Coahuila as N. m. micropus,
whereas Goldman (loc. cit.) considered
those from western localities in the state
as N. m. canescens.
Although the above studies either
lacked statistical treatment of data or
were limited to univariate analyses of
morphological characters, | Anderson
(1969) employed multivariate statistics
in comparisons of Neotoma micropus
with N. albigula from Chihuahua and
Coahuila. Multivariate statistics have
been used widely in studies of members
of the genus Canis (Jolicoeur, 1959; Law-
rence Bossert, 1967, 1969) and recently
have been employed in studies of geo-
graphic variation in bats (Smith, 1972),
shrews (Choate, 1970), and spiny mice
(Genoways, 1971). Geographic variation
in western subspecies of N. floridana and
all subspecies of N. micropus is consid-
ered here by means of a combination of
univariate and multivariate analyses.
MATERIALS AND METHODS
Age determination—Age of speci-
mens examined was determined by use
of a modification of the scheme devised
by Hoffmeister and de la Torre (1960:
479) for Neotoma stephensi. They rec-
ognized four age-groups based on degree
of eruption of upper molars and subse-
quent wear on these teeth. The oldest
and youngest categories in my arrange-
ment correspond in a general way to
those two groups as defined by Hoff-
meister and de la Torre. However, pre-
liminary calculations indicated that vari-
ance of mensural characters of rats in the
intermediate groups exceeded that ex-
pected. Age groups then were recon-
sidered and eight age classes were rec-
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 37
ognized as follow: Group I—immature
rats in which M3 is not occlusal and
often not erupted. Group I].—immature
rats in which M3 is occlusal, but with
the posterior loph of the tooth still iso-
lated. Group III.—rats with the dentine
of the posterior loph on M3 continuous
with that of the anterior loph and with
the labial reentrant angles of M2 and M3
continuing out of view into the alveolus;
the proximal termination of the labial
reentrant angles of M1 often is visible.
Group IV.—rats characterized by visible,
proximal terminations of reentrant angles
on all upper molars; the reentrant angles
of M1 are more than three-fourths as
long as the exposed portion of that tooth.
Group V.—young adults in which the
reentrant angles of M1 are shorter than
defined for group IV, but less than half
as long as the height of M1. Group VI.
adults with the reentrant angles of M1
between a third and a half as long as
the height of the tooth. Group VII.—
rats with visible reentrant angles on M1
that are less than a third as long as the
height of the tooth. Group VIII.—old
adults with no visible reentrant angles
on M1 but often with short reentrant
angles on M2 and M3. For reasons dis-
cussed beyond (see variation with age),
only specimens of age groups VI, VII,
and VIII were included in studies of
geographic variation when such speci-
mens were available, and males and fe-
males were treated separately (see sec-
ondary sexual variation). In two _ in-
stances it was necessary to include spec-
imens of age group V (the holotypes of
N. m. planiceps and N. m. leucophea
both are males of this age and older in-
dividuals were not available).
Molars of woodrats that had been
reared or maintained in the laboratory
were less worn than those of woodrats
that had not been in captivity. As a re-
sult, aging criteria described above were
not applicable in separating laboratory
animals into age groups comparable to
those of non-laboratory rats. Laboratory
specimens known to be more than two
years of age frequently were placed in
groups IV and V. Results of growth and
development studies, which will be pub-
lished elsewhere, indicated that labora-
tory woodrats essentially had ceased
growth by 30 weeks of age; this age then
was used as the critical age and only
laboratory woodrats more than 30 weeks
old were used in comparisons or treated
statistically. As discussed beyond, it was
found that laboratory woodrats were
larger in some measurements than their
non-laboratory counterparts from the
same localities. Thus, woodrats that had
been maintained in the laboratory in ex-
cess of one month were not included in
studies of geographic variation employ-
ing univariate analyses or in multivariate
analyses using CLSNT; a few were in-
cluded in MULDIS when other speci-
mens from critical areas were not avail-
able.
Pelage variation A Photovolt Photo-
electric Reflection meter (Model 610),
which yields values that are percentages
of reflection of pure white, was employed
to quantify color variation of woodrats.
Readings made for each of three reflec-
tions (red, green, and blue) were taken
from the lumbar region of museum spec-
imens of age groups VI-VIII character-
ized by unworn or relatively unworn
pelage. Analyses of adult molts and
pelages were made on museum skins.
The number and sequence of matura-
tional molts were studied on live wood-
rats in the laboratory; these data will be
included elsewhere in a discussion of
growth and development.
Qualitative cranial characters.—Three
cranial characters (Fig. 10) that have
been used as “taxonomic characters”
(Finley, 1958:248) were found to be
more variable than previously recorded.
The anterior palatal spine may be
pointed and nonbifurcate or distally
bifurcate. The presence and size of the
bifurcation was scored from one to five,
with “one” denoting absence of the fork.
The posterior margin of the hard palate
varies from having a relatively well-de-
fined medial indentation to having a
well-developed projecting medial con-
38 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
vexity. Variation in this character was
scored one to eight, with one being as-
signed to specimens with the deepest
indentation and eight to those with the
largest convexity. Size of sphenopalatine
vacuities was found to vary from nearly
closed in a few individuals to a large
opening extending anterior beyond the
posterior edge of the hard palate in
others; variation in this character was
scored one to six, from smallest to largest.
None of these characters lends itself to
precise measurements without more
sophisticated equipment than usually is
available. To insure consistency in scor-
ing, exemplary skulls were selected and
used for comparison in scoring other
specimens.
Bacular variation —Bacula of selected
adult male woodrats in the Museum of
Natural History of The University of
Kansas were prepared and stained ac-
cording to the method described by
Lidicker (1960:496), and subsequently
removed from phalli. Measurements of
bacula were taken to the nearest tenth
of a millimeter with the aid of a Wild
Heerbrugg Stereomicroscope, graph pa-
per, and dial calipers.
External and cranial size variation.—
External measurements (total length,
length of the tail, length of the hind foot,
and length of the ear from the notch)
were recorded from data on specimen
labels. These data were omitted if ob-
viously erroneous as recorded. Ten
cranial measurements were taken to the
nearest tenth of a millimeter. Seven of
the measurements were taken as illus-
trated and described by Hooper (1952:
9-11); these include greatest length of
skull, zygomatic breadth, least interor-
bital constriction (interorbital breadth),
length of rostrum, breadth of rostrum,
alveolar length of maxillary toothrow
(length of molar row), and length of
palatal bridge (length of palate). The
remaining three measurements were
taken as follow: condylobasilar length—
midline length of the skull from anterior-
most extensions of the premaxillae to the
posterior surface of the condyles; breadth
at mastoids—the distance, perpendicular}
to the longitudinal axis of the skull, from
the most lateral extension on one mastoid
to the same point of the other; and length
of nasals—the distance from the anterior
edge of the longest nasal to the most
posterior extension of either nasal.
Selection of samples.—Because there
were so few adults of each sex for statis-
tical treatment of specimens from indi-
vidual localities it was necessary to in-
clude those from adjacent localities in
pooled samples. Decisions for grouping
specific localities and establishing size of
geographic areas to include in each sam-
ple were based on several criteria. In no
case were specimens of different nominal
taxa, as recognized at the onset of the
study, included together in a single sam-
ple. In areas of suspected intergradation
or possible contact between species and
subspecies, an attempt was made to keep
size of geographic areas as small as pos-
sible. Whenever practical, localities were
grouped so that at least three and pre-
ferably no fewer than five adults of each
sex were available. Whenever the above
criteria could be met and there was no
cause to suspect biologically-based rea-
sons for doing otherwise, locality group-
ings often were made with consideration
to political boundaries merely to facili-
tate menial tasks such as sorting of orig-
inal data.
The thirty-two aggregate localities
(samples) and their identifying symbols
are shown in figure 8 and briefly outlined
below. When all available specimens of
a species or subspecies are included in a
single sample, the geographic area is not
described (exact localities were listed
previously under specimens examined).
Grouped localities of Neotoma floridana
were coded with numeric symbols and
those of N. micropus and the single sam-
ple of N. angustipalata were given alpha
symbols. Names given below in paren-
theses are those by which the woodrats
previously were recognized.
Sample 1—Neotoma floridana bai-
leyi.
Sample 2.—N. f. campestris from all
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 39
localities in Colorado and Nebraska.
_ Sample 3.—N. f. campestris from all
localities in Kansas west of a north-south
line extended from the boundary be-
tween Trego and Ellis counties.
Sample 4.—N. f. campestris from all
localities in Kansas east of the line de-
Iscribed for sample 3 and west of a paral-
lel line extended from the boundary be-
tween Russell and Ellsworth counties.
| Sample 5—N. f. attwateri (N. f.
osagensis) from all localities in Kansas
east of the line described for sample 4
and west of a parallel line extended from
Fic. 8. Sketch map of region in which
woodrats were studied showing general geo-
graphic areas of grouped localities, indicated by
identifying code symbols. All samples of Neo-
toma floridana (1-13) are represented by nu-
meric symbols and those of N. micropus (A-P)
and N. angustipalata (R) are represented by
alpha symbols. Solid lines separate the distri-
butions of species and dashed lines the distribu-
tions of subspecies. The solid dot labeled S in
Oklahoma marks the single known locality of
sympatry between two of the species. See text
for precise definitions of the area included in
each grouped locality.
the boundary between Saline and Dick-
inson counties.
Sample 6.—N. f. attwateri (N. f.
osagensis) from all localities in Kansas
east of the line described for sample 5
and north of a perpendicular line ex-
tended from the boundary between Lyon
and Greenwood counties.
Sample 7.—N. f. attwateri (N. f.
osagensis) from all localities in Kansas
south of the line described for sample 6.
Sample 8—N. f. attwateri (N. f.
osagensis) from all localities in Okla-
homa west of a line extended from the
boundary between Major and Garfield
counties.
Sample 9.—N. f. attwateri (N. f.
osagensis) from all localities in Oklahoma
east of the line described for sample 8
and north of a perpendicular line ex-
tended from the boundary between
Lincoln and Pottawatomie counties.
Sample 10.—N. f. attwateri (N. f.
osagensis) from all localities in Oklahoma
east of the line described for sample 8
and south of the line described for sam-
ple 9.
Sample 11—N. f. attwateri (N. f.
osagensis) from all localities in Texas
north of a line extended from the boun-
dary between Navarro and Limestone
counties and west of a perpendicular line
extended from the boundary between
Harrison and Gregg counties.
Sample 12.—N. f. attwateri from all
localities in Texas south of the east-west
line described for sample 11 and south-
west of a line extended from the south-
western border of Walker County where
it abuts Montgomery County.
Sample 13.—N. f. rubida from all lo-
calities in Texas.
Sample A.—N. micropus canescens
from all localities in Colorado, and in
Cimarron County, Oklahoma.
Sample B.—N. m. canescens from all
localities in Kansas northwest of U.S.
highway 54, and in Beaver and Texas
counties, Oklahoma.
Sample C.—N. m. canescens from all
localities in Meade and Clark counties,
40 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
Kansas, and in Harper County, Okla-
homa.
Sample D.—N. m. canescens (N. m.
micropus) from all localities in Barber,
Comanche, and Kiowa counties, Kansas.
Sample E.—N. m. canescens from all
localities in New Mexico except the
White Sands National Monument.
Sample F.—N. m. canescens from all
localities in Texas north of a line ex-
tended from the boundary between An-
derson and Winkler counties and west
of a perpendicular line extended from
the boundary between Fisher and Curry
counties.
Sample G.—N. m. canescens (N. m.
micropus) from all localities in Oklahoma
north of the South Canadian River, ex-
clusive of localities in samples A, B,
and C.
Sample H.—N. m. canescens (N. m.
micropus) from all localities in Oklahoma
south of the South Canadian River.
Sample I—N. m. canescens (N. m.
micropus) from all localities in Texas
north of the east-west line described for
sample F, and east of the north-south line
described for that sample.
Sample J.—N. m. canescens from all
localities in Chihuahua and those in
Texas south of the east-west line de-
scribed for sample F and west of a line
extended from the boundary between
Reagan and Irion counties.
Sample K.—N. m. canescens (N. m.
micropus) from all localities in Texas east
of the line described for sample J, south
of the east-west line described for sample
F, west of a line extended from the
boundary between Medina and Bexar
counties, and north of the Webb-Zapata
County boundary.
Sample L.—N. m. canescens (N. m.
micropus) from all localities in Texas
south of the east-west line described for
sample F and the Webb-Zapata County
boundary, and east of a north-south line
extended south to the southern Webb
County boundary from the boundary be-
tween Medina and Bexar counties.
Sample M.—N. m. canescens (N. m.
micropus) from all localities in Coahuila
and Nuevo Leon and those in Tamaulipas
north of an east-west line passing through
Reynosa.
Sample N.—N. m. micropus from all
localities in Tamaulipas south of the line’
described for sample M and north of 23°
30’ N latitude.
Sample O.—N. m. canescens (N. m.
leucophea) from White Sands National
Monument in New Mexico.
Sample P.—N. m. micropus (N. m.
littoralis) from all localities in Tamaulipas
south of 23° 30’ N latitude.
Sample Q.—N. m. planiceps.
Sample R.—N. angustipalata.
Sample $.—Neotoma_ floridana, N.
micropus, and their natural hybrids from
3 mi S Chester, Major Co., Oklahoma.
Statistical analyses.—Statistical anal-
yses were selected for their appropriate-_
ness, ease of interpretation, and avail-
ability at The University of Kansas Com-
putation Center. Standard _ statistics
(mean, range, standard deviation, stand-
ard error of the mean, variance, and
coefficient of variation) were calculated,
after which group-means were simul-
taneously tested for significant differ-
ences at the 0.95 level of confidence (0.05
level of significance) by single classifica-
tion analysis of variance (univariate
ANOVA). If significant variation was
present among the group-means and if
more than two samples were being com-
pared, the Sums of Squares Simultaneous
Testing Procedure (SS-STP) described
by Gabriel (1964) was employed to de-
termine maximal non-significant subsets.
Calculations involved in the SS-STP were
outlined by Sokal and Rohlf (1969:582),
and use of the procedure in studies of
geographic variation was considered by
Gabriel and Sokal (1969). All of the
above calculations were computed by
Power's UNIVAR program (Power, 1970).
Univariate analyses first were con-
ducted to compare males and females by
selecting samples of woodrats considered
to be adults that were from the same geo-
graphic areas (ideally, animals from a
single locality would be used, but no suf-
ficiently large samples were available).
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 41
When it was clear that significant sexual
dimorphism existed, samples of the pre-
viously described age groups were com-
pared separately within each sex. Re-
sults indicated that animals of age groups
V and younger frequently were signifi-
cantly smaller than those in groups VI
or older. Although animals in group VI
occasionally were significantly smaller
than those of groups VII and VIII, these
three age groups were considered to-
gether with sexes being treated separ-
ately in analysis of geographic variation.
So-called Dice-grams (Dice and Leraas,
1936) have been employed frequently to
illustrate a general array of variation.
For reasons discussed by Sokal and
Rinkel (1963), Dice-grams are not ap-
propriate for determination of statistical
significance when more than two samples
are being compared; therefore, all deter-
minations of significance or the absence
thereof were based on SS-STP tests.
Because the sample of specimens from
each locality usually exhibited various
subset relationships with samples from
other localities when different characters
were considered, it was necessary to use
multivariate analyses to determine rela-
tionships based on all characters exam-
ined. This was accomplished by means
of two programs (CLSNT-Version 2, and
MULDIS) available in the Numerical
Taxonomy System at the Computation
Center of The University of Kansas.
CLSNT was used to compare samples of
populations for geographic variation by
considering the sample of specimens
from each aggregate locality as an Oper-
ational Taxonomic Unit (OTU) and
sample means as characters. When only
a single individual was available, as for
Neotoma micropus planiceps, the char-
acters of that specimen were treated as
means. Discriminant function analysis
(MULDIS) was employed to compare
individuals from various samples and to
analyze for hybridization and intergrada-
tion.
Among other sets of values, CLSNT
and optional subroutines as employed by
me computed matrices of Pearson’s prod-
uct moment correlations and matrices of
taxonomic distance coefficients (see
Sokal, 1961, and Sokal and Sneath, 1963).
Each matrix was then subjected to clus-
ter analyses using UPGMA (unweighted
pair group method using arithmetic aver-
ages), and a two-dimensional phenogram
was generated from each. A coefficient
of cophenetic correlation (Sokal and
Sneath, 1963) was computed to express
the reliability of the phenogram based
on comparisons with the respective
matrices. Moss (1968) discussed rela-
tionships of the two phenograms and ex-
perimentally studied general types of
variation affecting each. I have consid-
ered both matrices and both phenograms
in all analyses, but because coefficients
of cophenetic correlation usually were
higher between the distance matrix and
phenogram, these have been given
greatest consideration. All computations
for CLSNT were conducted on stand-
ardized data, which was derived by con-
verting the mean for each character to
zero and the variance and standard devi-
ation to one so that the value for each
character was expressed in terms of
standardized deviates (see Sokal and
Rohlf, 1969:109 ).
A principal components analysis also
was conducted on the among-characters
correlation matrix to “condense” or “com-
press” the variation in the characters con-
sidered into a smaller number of “new”
characters, the first few principal com-
ponents. At least the first three com-
ponents were extracted in all cases and
the first five components frequently were
considered, especially when the number
of characters for each OTU was large.
The percentage of the total variation ac-
counted for by each principal component
also was calculated. OTU’s were pro-
jected onto the principal components, and
bivariate scatter diagrams were made by
plotting projections of OTU’s on all
combinations of components. Projection
of OTU’s into three-dimensional draw-
ings was accomplished with a PROJ-3D
program whereby the first three prin-
cipal component scores of each OTU
A2 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
were transferred to a magnetic tape from
which a Benson-Lehner incremental plot-
ter made the perspective drawings. The
shortest minimally connected network
between OTU’s was computed from the
matrix of distance coefficients and in-
cluded on the three-dimensional models.
Discriminant function analysis
(MULDIS) employs variance-covariance
mathematics to differentially weight each
character relative to the variance within
and between groups of that character
when two reference samples are con-
sidered. A discriminant multiplier ( dis-
criminant function) was calculated for
each variable; then each discriminant
multiplier was multiplied by the value of
its respective variable and summed for
all variables to yield a discriminant score
for each OTU. The discriminant scores
then were plotted on a frequency histo-
gram to compare the individuals of two
populations, with or without additional
comparisons of a test sample of geo-
graphic intermediates or suspected and
known (laboratory-bred ) hybrids.
NON-GEOGRAPHIC VARIATION
In order to undertake a meaningful
assessment of geographic variation, it is
necessary to understand the non-geo-
graphic variation that exists in popula-
tions of the organisms to be compared.
I have analyzed variation with respect
to age, secondary sexual characteristics,
individual differences, and effects of hav-
ing been held in captivity. Variation in
pelages resulting from age and molts was
considered and was found to vary sea-
sonally. Because seasonal timing of molt
and certain characteristics of pelage in
woodrats vary geographically, these as-
pects are considered beyond with dis-
cussion of geographic variation in color.
Variation with Age
Variation in size correlated with age
differences was analyzed for samples of
Neotoma floridana campestris (Table 1),
N. f. baileyi, N. f. attwateri, and N. mi-
cropus canescens (Birney, 1970). Be-
cause age-groups and sexes were sepa-
rated sample size frequently was small,
especially for baileyi. As a result, some
age-groups were strikingly different in
size, but the differences were not always
statistically significant.
Dimensions of two external charac-
ters (length of hind foot and length of
ear) and those of two cranial characters
(least interorbital constriction and alve-
olar length of the maxillary toothrow)
were influenced less by age than were
those of other characters. Growth and
development studies of laboratory wood-
rats demonstrate that the hind foot and
ear grow at a disproportionately faster
rate than the body and tail. Also, varia-
tion in external measurements of museum
specimens is high (see discussion of indi-
vidual variation) because of inconsis-
tencies in techniques used to measure
these characters by various collectors.
Alveolar length of the maxillary tooth-
row does not increase with age after the
molars have become occlusal, because
individual teeth of woodrats do not in-
crease in diameter after eruption. There
is a tendency for the molar row to be
slightly longer in rats of age-groups III
and IV than in older animals. The alve-
olar tissue in cleaned skulls of older
woodrats usually is separated slightly
from the base of the teeth and in some
senile rats the molar roots extend to the
alveolus. These factors tend to result in
smaller measurements, and a decrease in
accuracy of the measurement. Least
interorbital constriction shows a general
increase in size up to age-groups III and
IV. Sequence of means varied noticeably
in the older age-groups, indicating that
the constriction changes little with age
after the early period of rapid growth.
Dimensions of other cranial charac-
ters indicated that animals in age-groups
VII and VIII do not differ significantly
in size. Although the mean of a sample
in age-group VI frequently was less than
that of older woodrats, this difference
seldom was significant. Highest F,
values and the greatest number of non-
significant subsets frequently were com-
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA
TABLE 1. Variation with age in 14 external and cranial measurements of Neotoma floridana
campestris. Fs; was calculated by single classification analysis of variance.
are at the P 0.05 level of significance; ns indicates no significant difference within a group of
means.
Tabular F values
Nonsignificant subsets (as calculated by the Sums of Squares Simultaneous Testing
Procedure ) of significantly different groups of means are shown in the last column.
Measurement,
sex, and F,
age class N Mean se SIR Range CV F SS=Sie
Total length
Females
VIII 15 370.8 8.70 (340.0-402.0) 4.54 22.88 I
VI 16 369.6 8.88 (340.0-409.0) 4.81 PPA) | I
VII 10 268.7 11.39 (344.0-395.0) 4.88 I
V 20 353.5 6.72 (325.0-377.0) 4.95 il
IV 14 337.0 8.91 (303.0-365.0) 4.94 ll
Ill 13 314.2 1s) (291.0-374.0) Ugaie: Ib AL
II 2 284.0 24.00 (272.0-296.0) 5.98 I
Males
VIII ul 399.7 15.56 (371.0-434.0) 5.15 30.90 I
VI 1 382.8 9.84 (350.0-408.0) 4.26 25 I
V 117 377.6 13.19 (325.0-42.4.0) 7.20 eel
VII 9 373.9 10.30 (341.0-395.0) 4.13 owe
IV 13 347.8 12.54 (307.0-383.0) 6.50 Ik 1
Ill 7 302.0 21.00 (288.0-365.0) 8.38 I
I 3 264.7 SMILE (232.0-286.0) 10.85 I
II 6 264.3 17.82 (240.0-287.0) 8.26 I
Length of tail vertebrae
Females
VI 16 156.6 4.54 (144.0-172.0) 5.80 13.65 I
VIII 15 154.5 4.85 (136.0-175.0) 6.07 SH I
VII 10 154.5 7.46 (138.0-172.0) meOo Me i
V 20 148.4 4.86 (131.0-167.0) Weoo ie
IV 14 142.2 St3D (133.0-152.0) 4A] ial
Ill 13 130.8 5.48 (115.0-154.0) 7.56 if at
Il 2 122.5 25.00 (110.0-135.0) 14.43 I
Males
VIII 7 164.4 6.38 (@USIRO=175!0) Bale 17.39 I
VI 11 161.0 8.33 (130.0-178.0) 8.58 25 I
Vv 17 155.9 6.53 (132.0-177.0) 8.64 I
VII 9 151.6 9.17 (120.0-164.0) 9.07 ou
IV 13 146.8 6.08 (129.0-168.0) TAT if al
Ill i IB PATE 9.77 (107.0-147.0) 9.73 Idi
I 3 113.0 21.94 (92.0-129.0) 16.81 I
II 6 108.5 8.53 (98.0-124.0) 9.63 I
Length of hindfoot
Females
IV 14 39.9 1.10 (36.0-43.0) Salle ee 100 ns
VI 16 39.7 0.60 (38.0-42.0) 3.01 2.21
V 20 39.4 0.69 (36.0-41.0) 3.90
VIII 16 39.2 0.71 (36.0-41.0) 3.64
VII 10 39.1 1.28 (36.0-42.0) 5.18
Ill 13 38.8 1ek3 (35.0-41.0) 5.24
II 2, 38.0 4.00 (36.0-40.0) 7.44
43
44
MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
TABLE 1.—Continued.
Measurement,
sex, and F,
age class N Mean =+ 2SE Range CV F SS-STP
Males
VII 4 40.8 0.88 (39.0-43.0) 3.43 4.84 I
VIII 8 40.8 1.50 (36.0-44.0) 6.35 2.14 I
V 10 40.6 0.90 (36.0-44.0) 4.73 if
VI 5 40.4 1.24 (37.0-44.0) Sell I
IV of 40.0 1.01 (35.0-42.0) 4.56 dt
III 5 38.9 1.34 (37.0-41.0) 4.56 I I
II 5 36.7 B52: (35.0-40.0) 5.08 I
I 3 36.7 0.67 (36.0-37.0) Sir I
Length of ear
Females
VIII 8 28.0 1eOT (26.0-30.0) 5.40 1.36 ns
VI 12 oS 1.18 (25.0-32.0) sey? 27S)
VII 5 Die, 1.47 (25.0-29.0) 6.04
IV 9 272, 1.19 (25.0-30.0) 6.57
V 6 27.0 0.89 (25.0-28.0) 4.06
Ill 9 26.4 eat (25.0-30.0) 6.30
II 2 25.0 4.00 (23.0-27.0) 1ST
Males
VI 5 29.0 2.28 (26.0-33.0) 8.79 1.70 ns
IV 7 28.9 1.60 (26.0-32.0) Us 2.26
VII 8 28.6 2.28 (26.0-33.0) 8.79
VII 4 28.5 0.58 (28.0-29.0) 2.03
V 8 28.5 1.00 (26.0-30.0) 4.96
Ill 5 26.0 1.41 (24.0-28.0) 6.08
Il 5 25.6 1.36 (24.0-28.0) 5.92
I 3 25.0 ISIS) (24.0-26.0) 4.00
Greatest length of skull
Females
VIII 14 49.9 0.69 (48.3-52.1) sy 24.01 I
VI 13 49.4 0.87 (47.0-53.3) 3.18 8) I
VII 8 49.3 0.86 (47.5-51.8) 9,45 Jha
V 19 47.3 4.19 (45.8-49.5) 1.93 It) dL
IV 14 46.7 0.57 (44.4-48.1) 2.28 I
III 10 44.9 fay) L (42.5-48.3) roll
II 2 41.8 2.90 (40.4-43.3) 4.90
Males
VIII 10 51.8 ALS (49.5-55.2) 3.44 32.64 I
VII 6 51.6 1.30 (49.0-53.4) 3.08 De lil I
V 20 49.8 0.76 (47.3-53.7) 3.40 I
VI 9 49.7 1.52 (46.0-52.7) 4.60 eo
IV 13 46.8 0.95 (43.3-49.6) 3.66 Pel
Ill 4 44.4 2.25 (42.3-47.4) 5.06 I
I 1 40.9 oat (40.9-40.9) a I
Il 5 39.2 2.19 (37.1-42.7) 6.26
Condylobasilar length
Females
VIII 15 48.4 0.75 (46.9-51.6) 2.98 36.40 I
VII 8 48.3 0.90 (46.4-50.9) 2.63 228 I
VI 10 47.3 0.67 (45.2-48.9) D2 eT
V 20 45.7 0.45 (44.0-48.2) DON ive i
IV 14 44.6 0.57 (42.7-46.3) DBM I
Ill 12 42.4 127 (39.9-45.6) 5.19
Il 2 39.3 2.60 (38.0-40.6) 4.68
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA
TABLE 1—Continued.
Measurement,
sex, and Fy
age class N Mean + 2SE Range CV F SS-STP
Males
VIII 12 50.6 1.07 (48.1-54.3) 3.66 36.44 I
VII ll 49.6 1.63 (46.6-52.3) 4.32 OIL I
VI 9 48.3 EAN (44.5-52.3) 4.57 I
V 20 48.2 0.82 (45.3-52.8) 3.82 I
IV 13 44.7 0.95 (41.1-46.8) 3.81 I
III 4 42.0 2.94 (39.6-46.1) 6.99 I
I 1 38.6 a (38.6-38.6) ets if at
II 5 36.7 2.09 (34.8-40.1) 6.38 I
Zygomatic breadth
Females
VIII 14 27.4 0.52 (26.0-29.6) 3.54 34.92 I
VII 6 26.8 0.54 (26.0-27.7) 2.46 OF8) I
VI 14 26.3 0.41 (25.1-28.0) 2.88 Io
V 19 25.6 0.36 (24.5-27 1) 3.09 eT
IV 14 24.7 0.33 (23.6-25.9) 9.54. if J
Ill 1} DN 0.54 (22.6-25.5) 4.15 I
II 2 ODT I5) 0.60 (22,.2-22.8) 1.89
Males
VIII 11 28.2 0.51 (27.0-29.9) 2.99 49.56 II
VII 7 HT/83 0.72 (26.1-28.5) 3.47 Dy I
VI 8 26.7 0.54 (25.4-28.1) 2.85 if I
V 19 26.6 0.44 (25.3-28.7) By aM/ I
IV 13 24.8 0.49 (23.4-26.4) 3.56 I
Ill 6 24.3 1.13 (22.9-26.1) 5.69 I
I 3 20.6 1.64 (19.0-21.7) 6.88 I
II 5 20.5 1.30 (18.9-22.6) 7.07 I
Least interorbital constriction
Females
VI 15 6.8 0.19 (6.1-7.5) 5.55 01 ns
VII 9 6.7 0.17 (6.2-7.0) 3.78 Reon
VIII 16 6.6 0.13 (6.2-7.1) 3.92
V 20 6.6 0.12 (6.1-7.1) 4.07
IV 14 6.6 0.12 (6.1-6.9) 3.49
Ill 14 6.5 0.18 (6.0-7.3) Bulli
II 2 6.2 0.10 (6.1-6.2) eas
Males
VII 10 7.0 0.23 (6.5-7.7) 5.19 5.97 I
VIII 1b 6.8 0.13 (6.5-7.1) 3.32 2.14 el
VI 10 6.8 0.18 (6.4-7.1) 4.20 1 fe ay Dee |
V 20 6.7 0.11 (6.2-7.2) 3.60 | ae! Lee) aL
Ill 0 6.6 0.20 (6.3-6.9) 3.97 LPS is V1
IV 13 6.5 0.18 (GET) 4.90 Jy toe a
Il 6 6.4 0.31 (5.9-6.9) 5.87 eral
I 3 6.2 0.2 (6.1-6.4) 2.79 I
Breadth at mastoids
Females
VIII 15 19.4 0.36 (18.3-21.0) 3200 7.96 I
VI JUL 19.3 0.40 (18.1-20.2) 3.42 depo} I
VII 10 19.2 0.38 (18.1-20.0) Bip 1 Ib ou
V 19 18.7 0.20 (17.9-19.7) 2.32 Thy ace I
IV 13 18.7 0.20 (17.9-19.2) 1.91 Liet
Ill 1 18.3 0.30 (17.7-19.5) 2.82 I
II 2 17.9 0.60 (17.6-18.2) ROT I
45
46 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
TABLE 1.—Continued.
Measurement,
sex, and F,
age class N Mean + 2SE Range GN. F SS-STP
Males
VIII ill 20.5 0.51 (19.3-22.4) 4.15 16.91 I
VII 10 19.6 OSS (18.7-20.2) 2.66 Dall AL
V 20 19.6 0.37 (18.3-20.8) 4,20 It lt
VI 8 19.1 0.73 (17.4-20.3) 5.43 eel:
IV 13 18.7 O27 (17.6-19.6) 2.59 100
Ill 5 18.6 0.36 (18.1-19.0) OR AUTl LoL
II 6 17.0 0.48 (16.3-17.7) 3.45 I
I 1 16.9 (16.9-16.9) z I
Length of rostrum
Females
VII 10 19.5 0.51 (18.2-21.0) 4,11 19.25 I
VIII 15s 19.4 0.29 (18.6-20.5) 2.92 OPAL I
VI 16 19.0 0.44 (17.3-21.1) 4.62 1 Gate
V 19 18.3 0.26 (17.5-19.8) 3.14 I
IV 15 18.1 0.36 (16.7-19.4) 3.84 eel
Ill 12 ie, 0.61 (15.9-18.6) 6.11 1
II 2, DES 0.90 (15.3-16.2) 4.04
Males
VIII 11 20.5 0.64 (19.4-22.9) 5.19 oil I
VII 8 20.4 0.44 (19.3-21.2) 3.08 Asi a! I
V 20 19.7 0.43 (18.0-21.7) 4.92 I
VI iat 19.2 0.51 (18.0-20.9) 4.38 Teer
IV 133 18.2 0.49 (16.4-19.6) 4.88 I
Ill 6 ies 0.95 (16.1-18.8) 6.66 i
I 3 14.7 1.92 (12.8-15.9) ES. I
II 6 14.4 0.94 (13.2-15.6) 7.99 I
Breadth of rostrum
Females
VIII 16 8.5 0.17 (8.0-9.4) 4.10 8.62 I
VII 9 8.5 Q:211! (8.0-9.0) 3.64 DADA I at
VI 15 8.2 0.12 (7.7-8.5) 2.84 1 ed |
Vv 20 8.1 0.15 (iz3=8:0) 4.1] ge da cif
IV 15 7.9 1.16 (7.4-8.4) 3.89 Ihe dl
Ill 13 7.8 0.23 (7.3-8.5) 5.20 I
II 1 7.6 (7.6-7.6) Es I
Males
VIII 12 8.9 0.14 (8.6-9.3) 2.64 iyeay I
VII 9 8.6 0.24 (8.2-9.2) 4.10 2.14 lope |
V 20 8.4 0.17 (7.8-9.4) 4.54 iT, ie
VI 11 8.2 0.46 (6.1-8.8) 9.35 it
IV 13 8.1 0.20 (7.5-9.0) 4.58 Teele ll
III 7 Voll 0.23 (7.2-8.1) 3.90 Pes “1
II 6 7.0 0.44 (6.3-7.6) 7.79 ek
I 3) 7.0 0.46 (6.6-7.4) thal I
Alveolar length of maxillary toothrow
Females
IV 15 9.9 0.17 (9.3-10.5) 3.31 2.32 I
VII 10 9.8 0.17 (9.4-10.3) STIS: DO ie
V 20 9.7 0.14 (9.1-10.3) SHS if Ut
VI 16 9.7 0.17 (9.3-10.5) 3.49 lel
Ill 13 9.7 0.13 (9.4-10.1) 2.41 1b
II 9) 9.6 0.50 (9.3-9.8) 3.70 Lael:
VIII 16 9.5 0.18 (8.9-10.0) 3.82 I
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA AT
TABLE 1.—Concluded.
Measurement,
sex, and Fy
age class N Mean + 2SE Range GY F SS-STP
Males
V 20 9.9 0.12 (9.2-10.4) 2.64 2.13 ns
| IV 13 9.9 0.19 (9.3-10.6) 3.43 2.14
Ill il 9.8 0.19 (9.6-10.3) 2255
VIII 2, 9.7 0.26 (9.0-10.4) 4.68
VII 10 9.7 0.26 (8.9-10.2) 4,22,
VI 11 9.6 0.23 (9.1-10.3) 4.05
I 3 9.5 0.18 (9.3-9.6) 1.61
II 6 9.4 0.28 (8.9-9.8) 3.66
Length of palatal bridge
Females
VII 10 8.6 0.20 (8.0-9.1) OHhe 4.91 I
VIII 16 8.5 0.25 (7.8-9.4) 5.96 SHOAL lie
VI 16 8.2 On (7.5-8.8) 4.13 Hk Al
Vv 20 8.2 0.15 (7.4-8.7) 4.15 I I
IV T5 8.1 0.19 (7.3-8.6) 4,44 |e |
Ill 13 8.1 0.16 (7.6-8.8) 3.67 I
II 2; 7.6 0.10 (7.6-7.7) 0.92 I
Males
VII 9 9.0 0.44 (7.9-9.8) TAT 14.27 I
VIII 12 9.0 0.21 (8.5-9.7) 4.05 2.14 Ti
VI 11 8.5 0.25 (7.6-9.0) 4.81 1 Oa gay
V 20 8.4 0.23 (7.4-9.5) 6.15 le eel
III 6 8.1 0.33 (7.6-8.7) 4.96 ee el
IV 13 7.9 0.18 (7.4-8.4) 4.07 1s ent
I 2 7.4 0.60 (7.1-7.7) Bo eat
II 6 wal 0.41 (6.5-7.9) 7.02 I
Length of nasals
Females
Vill 15 19.4 0.30 (18.7-20.4) 3.03 20.54 I
VII 10 19.3 0.36 (18.4-20.4) 2.96 PAPAL I
VI 16 18.9 0.44 (17.6-20.3) 4.70 they ae
V 19 18.1 0.25 (17.2-19.3) 3.04 ie
IV 15) 17.9 0.42 (16.2-19.2) 4,55 I al
III 12 16.8 0.61 (15.4-18.5) 6.26 eyl
II 2 16.0 2.00 (15.0-17.0) 8.84 I
Males
VII 8 20.3 0.42 (19.1-21.0) 2.94 29.19 I
VIII 11 20.2 0.83 (18.3-23.3) 6.77 2.14 I
V 20 19.5 0.43 (18.3-21.5) 4.90 | (ta
VI ma 19.0 0.60 (17.7-20.5) p20 leer ey
IV 13 18.1 0.52 (16.0-19.5) 5.21 jlo |
III 6 17.0 IB? (15.5-19.0) 8.06 IF
I 3 14.8 2.07 (12.8-16.2) 12.10 lel
II 6 14.4 0.91 (1333-1557) 7.69 I
puted for measurements involving di-
mensions of the anterior portions of
skulls. In studies of Neotoma micropus,
Allen (1894a:240) noticed that relative
growth of the preorbital region exceeded
that of the postorbital area in post-
partum development. Hall (1926:396)
observed similar relative rates of growth
for Spermophilus beecheyi and con-
sidered them a common feature of mam-
malian development. Therefore, it was
expected that measurements such as
length of rostrum and length of nasals
would be most critical in terms of group-
48 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
ing animals of different ages for other
analyses. Animals of age-group V_ usu-
ally were significantly different from
animals of older groups, thus indicating
that specimens of age-group V_ should
not be included with older woodrats. Al-
though this resulted in reduction of the
sizes of available samples, comparisons
of smaller, more homogeneous samples
are more reliable than those involving
heterogeneous samples.
Secondary Sexual Variation
Although no detailed analytical tests
comparing woodrats of different sexes
from the same geographic areas are avail-
able, males and females generally have
been treated separately in studies of
geographic variation (Hooper, 1938,
1940; Hoffmeister and de la Torre, 1960).
However, Schwartz and Odum (1957)
apparently treated both sexes of N. flori-
dana in the same samples. Using only
specimens of age groups VI, VII, and
VIII, males and females were tested by
single classification ANOVA to deter-
mine if secondary sexual variation was
present in external and cranial dimen-
sions of N. f. baileyi, N. f. campestris, N.
f. attwateri, N. m. micropus, and N. m.
canescens (Table 2).
In one sample, N. f. campestris, size
variation attributable to sex was ob-
served in most measurements. Samples
of campestris generally included more
individuals than other samples. Means
for males were larger at the 0.01 level
of significance (P < 0.01) in eight of the
14 measurements, and significantly larger
(P <0.05) in two of the remaining six.
Only in length of ear did the mean for
females exceed that for males. In N. m.
micropus, the taxon represented by few-
est individuals, no significant differences
in means were detected, but means of
measurements for males were larger than
those for females in nine characters. This
suggests that non-significant results were
a function of the small samples rather
than absence of real differences between
sexes. Males of baileyi were found to be
larger than females in only six measure-
ments and the difference was significant
only in one (least interorbital constric-
tion). Size of females exceeded that of
males in three characters, but the dif-
ference was significant in none. Means
accurate to the nearest tenth of a milli-
meter were identical in five dimensions
considered. Although larger samples
might alter the results, it appears that
baileyi has less secondary sexual varia-
tion than other taxa considered. Samples
of canescens and attwateri were rela-
tively large. Seven significant differences
(one at the 0.01 level and six at the 0.05
level) apparently resulting from secon-
dary sexual variation were observed for
attwateri, whereas only four (one at the
0.01 level and three at the 0.05 level)
were exhibited by canescens.
Significant secondary sexual variation
was not demonstrated for length of tail
vertebrae, length of ear, breadth of ros-
trum, and alveolar length of maxillary
toothrow. Total length, condylobasilar
length, and length of nasals varied sig-
nificantly between the sexes in all of the
taxa having samples of more than 10
individuals of each sex.
When all taxa and characters are
considered, it is seen that sufficient sec-
ondary sexual variation exists to discour-
age treatment of males and females as
a single sample. Therefore, the sexes
were treated separately in geographic
considerations of mensural data. Spec-
imens of both sexes were treated as a
single sample in only one set of analyses
that included mensural data (discrim-
inant function analysis). Because dis-
criminant function analysis was used in
comparisons of individuals and not in
comparisons of sample means, the sex
of each individual could be considered
when interpreting results.
As discussed beyond (comparative
reproduction), it was observed in the
laboratory that males capable of phys-
ically dominating females in breeding
cages were the more successful breeders
and, conversely, females that were phys-
ically subordinate were more successful
breeders than large dominant females.
Thus secondary sexual variation in size
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 49
TABLE 2. Secondary sexual variation in 14 external and cranial measurements of selected
samples of adult Neotoma floridana and N. micropus. Fs was calculated by single classification
analysis of variance. Tabular F values are given at the level of significance or at P<0.05 if not
significant. One asterisk and two asterices indicate significance at P<0.05 and P<0.01, re-
spectively, whereas ns indicates no significant difference.
Measurements F
and sex N Mean a= PSF Range CV F
Sample 1 (Neotoma floridana baileyi)
Total length
Females 9 374.4 9.87 (350.0-393.0) 3.95 < 1.00
Males ui 381.3 10.04 (361.0-398.0) 3.48 4.60 ns
Length of tail vertebrae
Females 9 161.7 9.00 (136.0-180.0) 8.35 <1.00
Males it 159.7 10.20 (138.0-176.0) 8.44 4.60 ns
Length of hind foot
Females iil 39.1 0.51 (38.0-41.0) 2.14 3.00
Males 8 39.8 0.60 (38.0-41.0) Dal2 4.45 ns
Length of ear
Females 5 26.6 1.20 (25.0-28.0) 5.04 <1.00
Males 2 205 3.00 (26.0-29.0) Tata 6.61 ns
Greatest length of skull
Females ll 48.8 0.44 (47.5-49.7) 15m! < 1.00
Males 7 48.4 iil (46.5-50.7) 3.03 4.49 ns
Condylobasilar length
Females fat. 47.4 0.55 (46.0-48.9) 1.92 <1.00
Males i 47.4 Lay, (45.7-49.8) SHOE 4.49 ns
Zygomatic breadth
Females 11 26.1 0.27 (25.4-26.6) 2; < 1.00
Males of 25.9 0.61 (24.8-27.1) 3.10 4.49 ns
Least interorbital constriction
Females ia 6.7 0.15 (6.3-7.0) 3.63 6.34
Males 9 6.9 0.17 (6.6-7.4) 3.68 4,41*
Breadth at mastoids
Females 11 19.0 0.13 (18.2-19.6) 230 <1.00
Males 8 19.0 0.51 (18.0-20.4) 3.79 4,45 ns
Length of rostrum
Females Tet 18.8 0.32 (17.5-19.4) 2.86 <1.00
Males 8 18.9 0.43 (17.8-19.6) Sep 4.45 ns
Breadth of rostrum
Females eu 7.9 0.13 (7.5-8.2) 2.76 < 1.00
Males 9 7.9 On (7.5-8.2) 3.26 4.41 ns
Alveolar length of maxillary toothrow
Females 1 9.4 O17 (8.8-9.9) 3.07 < 1.00
Males 9 9.5 0.20 (9.2-10.0) 3.10 4.41 ns
Length of palatal bridge
Females ii 8.7 0.34 (7.3-9.2) 6.42 < 1.00
Males 9 8.7 0.33 (8.2-9.6) 5.66 441 ns
Length of nasals
Females 11 18.7 0.33 (18.0-20.2) 2.96 <1.00
Males 8 18.7 0.43 (17.6-19.4) oe22) 4.45 ns
50 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
TABLE 2.—Continued.
Measurements F,
and sex N Mean Se) Os) By Range GV F
Samples 2, 3, and 4 (Neotoma floridana campestris)
Total length
Females 4] 369.8 roo (340.0-409.0) 4.61 10.42
Males 27 384.2 7.47 (341.0-434.0) 5.05 7.04 **
Length of tail vertebrae
Females Al 1553 3.03 (136.0-175.0) 6.24 1.48
Males 27 158.7 ball? (120.0-178.0) 8.37 3.99 ns
Length of hind foot
Females 42, 39.4 0.46 (36.0-42.0) 3.80 9.71
Males 33 40.6 0.72 (36.0-44.0) 5.07 70s
Length of ear
Females 25 27.8 0.71 (25.0-32.0) 6.35 3.02
Males 17 28.7 0.82 (26.0-33.0) 5.88 4.08 ns
Greatest length of skull |
Females 5) 49.6 0.46 (47.0-53.3) 2.76 10.02 |
Males 25 51.0 0.84 (46.0-55.2) 4.12 Tally
Condylobasilar length
Females 33 48.1 0.47 (45.2-51.6) 2.82 11.84
Males 28 49.6 0.83 (44.5-54.3) 4.43 Te
Zygomatic breadth
Females 34 26.8 0.32 (25.1-29.6) 3.53 6.53
Males 26 27.5 0.42 (25.4-29.9) 3.85 4:02)
Least interorbital constriction
Females 40 6.7 0.09 (6.1-7.5) 4.56 7.44
Males 32 6.9 0.10 (6.4-7.7) 4,29 Ol. =
Breadth at mastoids
Females 36 19.3 0.22 (18.1-21.0) 3:00 5.96
Males 29 19.8 0.37 (17.4-22.4) 4.97 4:00 =
Length of rostrum
Females Al 19.3 0.24 (17.3-21.1) 3.98 11.40
Males 30 20.0 0.38 (18.0-22.9) 5.26 1.047"
Breadth of rostrum
Females 40 8.4 0.10 (7.7-9.4) 3.97 3.35
Males 32 8.6 0.20 (6.1-9.3) 6.77 3.98 ns
Alveolar length of maxillary toothrow
Females 42, 9.6 0.11 (8.9-10.5) 3.60 < 1.00
Males 33 9.7 0.14 (8.9-10.4) 4.21 3.98 ns
Length of palatal bridge
Females 42, 8.4 0.13 (7.5-9.4) 5.06 12.48
Males 32 8.8 0.15 (7.6-9.8) 5.83 HAO
Length of nasals
Females 4] 19.2 0.23 (17.6-20.4) 3.84 7.91
Males 30 19.8 0.44 (17.7-23.3) 6.03 OA =
Samples 5, 6, and 7 (Neotoma floridana attwateri)
Total length
Females 20 364.6 8.89 (329.0-397.0) 5.45 8.28
Males 18 386.9 13.02 (345.0-450.0) 7.14 Moo HS
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA
TABLE 2.—Continued.
Measurements F,
and sex N Mean ae OAT Range CV F
Length of tail vertebrae
Females 20 1572 4,23 (142.0-170.0) 6.02 < 1.00
Males 18 160.1 4.18 (139.0-175.0) 5.54 4.11 ns
Length of hind foot
Females 21 38.1 0.96 (34.0-42.0) 5.75 4.51
Males 19 39.4 0.69 (36.0-42.0) 3.81 ANOe
Length of ear
Females 15 Dill 1.79 (23.0-38.0) 12.76 <1.00
Males 15 26.7 0.93 (25.0-30.0) 6.70 4.20 ns
Greatest length of skull
Females 21 49.4 0.70 (47.0-52.2) O25 5.49
Males 18 50.7 0.80 (47.4-53.5) 3.36 Ae
Condylobasilar length
Females 21 48.1 OFT. (45.6-51.7) 3.68 5.90
Males 18 49.6 0.87 (46.1-52.2) 3.74 Asli
Zygomatic breadth
Females 22 26.9 0.39 (25.6-29.1) 3.42 5.61
Males 17 WiLal 0.55 (25.7-29.2) 4,12 ALY *
Least interorbital constriction
Females 23 6.5 0.13 (6.1-7.2) 4.81 2.67
Males 20 6.7 0.18 (6.0-7.8) 6.01 4.08 ns
Breadth at mastoids
Females 23 19.2 0.31 (17.8-20.4) 3.84 5.98
Males 18 19.9 0.49 (16.9-21.0) 5.23 ANNO! =
Length of rostrum
Females al 19.2 0.32 (18.1-20.6) SRrlT Bl y/
Males 20 19.7 0.43 (17.9-21.5) 4.85 4.10 ns
Breadth of rostrum
Females 21 8.1 0.11 (7.7-8.5) 3.24 Sok
Males 19 8.3 0.21 (7.5-9.1) 5.45 4.10 ns
Alveolar length of maxillary toothrow
Females 23 9.4 1.54 (8.7-10.1) 3.95 2.63
Males 20 9.6 1.62 (9.0-10.2) 3.78 4.08 ns
Length of palatal bridge
Females P23) 8.5 1.60 (7.6-9.3) 4.50 SAT
Males 20 8.7 1.98 (7.9-9.6) 5.08 4.08 ns
Length of nasals
Females 20 19.1 0.36 (17.8-21.3) 4.17 6.03
Males 19 19.8 0.37 (18.0-21.6) 4,12 A
Samples B and C (Neotoma micropus canescens)
Total length
Females 31 355.8 5.97 (310.0-382.0) 4.67 7.11
Males 23 370.0 9.46 (334.0-411.0) 6.13 4.03 *
Length of tail vertebrae
Females 31 147.1 3.70 (130.0-165.0) 7.01 3.22
Males 23 152.6 5.10 (131.0-175.0) 8.01 4.03 ns
Length of hind foot
Females 30 38.4 0.54 (36.0-41.0) 3.85 1.95
Males 25 39.2 1.01 (35.0-45.0) 6.46 4.03 ns
51
52 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
TABLE 2.—Continued.
Measurements F,
and sex N Mean + 2SE Range CV F
Length of ear
Females 24 wile 0.56 (25.0-30.0) 5.10 <1.00
Males 16 PAfall 0.72 (25.0-29.0) 5.31 4.10 ns
Greatest length of skull
Females 2G 48.8 0.70 (44.2-51.8) 3.10 1.89
Males 25 49.5 0.63 (46.4-52.9) 3.17 4.03 ns
Condylobasilar Jength
Females 29 47.0 0.58 (42.8-50.0) 3.34 8.72
Males 24 48.3 0.66 (44.6-50.9) 3.33 Tale
Zygomatic breadth
Females 30 26.5 0.39 (24.7-29.1) 4.06 < 1.00
Males 26 26.7 0.36 (25.1-28.8) 3.47 4.03 ns
Least interorbital constriction
Females 32 6.3 0.10 (5.8-7.0) A472 < 1.00
Males OM 6.3 0.11 (5.8-6.9) 4,39 4.02 ns
Breadth at mastoids
Females 27 19.1 0.23 (17.9-20.3) 3.10 1.86
Males 24 19.3 0.28 (18.0-20.8) 3.58 4.04 ns
Length of rostrum
Females 30 18.9 0.27 (17.2-20.2) 3.98 (Gls)
Males 26 19.4 0.28 (17.8-20.7) 3.67 4035"
Breadth of rostrum
Females 32 8.3 0.14 (7.2-9.3) 4,92 < 1.00
Males ON 8.3 0.14 (7.5-9.2) 4.41 4.02 ns
Alveolar length of maxillary toothrow
Females 32 9.4 0.14 (8.5-10.1) 4.35 <1.00
Males 27 9.3 0.12 (8.7-10.1) 3.47 4.02 ns
Length of palatal bridge
Females 31 7.9 0.19 (7.1-9.5) 6.56 <1.00
Males 26 8.1 0.18 (6.8-8.9) ate 4.02 ns
Length of nasals
Females 30 19.2 0.35 (16.7-21.2) 5.04 6.03
Males 26 19.8 0.32 (18.0-21.1) 4.11 ALORS
Sample P (Neotoma micropus micropus)
Total length
Females 4 354.5 24.84 (333.0-377.0) 7.01 < 1.00
Males 3 364.3 24.04 (362.0-366.0) b.71 6.61 ns
Length of tail vertebrae
Females 4 1735 19.77 (155.0-193.0) 11.40 < 1.00
Males 3 169.7 4.06 (166.0-173.0) 2.07 6.61 ns
Length of hind foot
Females 4 36.5 1.29 (35.0-38.0) 3.54 2.76
Males 3 38.0 1 ss (37.0-39.0) 2.63 6.61 ns
Length of ear
Females 4 28.2 RO? (25.0-30.0) 7.85 < 1.00
Males 2 28.0 2.00 (27.0-29.0) 5.05 let ms
Greatest length of skull
Females 4 45.8 1.49 (43.9-47.1) Bab) 1.21
Males 3 46.6 0.42 (46.2-46.9) 0.77 6.61 ns
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 53
TABLE 2.—Concluded.
Measurements By
and sex N Mean + 2SE Range CV F
Condylobasilar length
Females 4 43,2 1.44 (41.7-44.5) 3.32 1.24
Males 3 44,2 0.75 (43.6-44.9) 1.47 6.61 ns
Zygomatic breadth
Females 4 24.0 0.38 (23.5-24.4) 1.57 3.88
Males 3 25.0 WLeIbe (24.4-26.2) 4.04 6.61 ns
Least interorbital constriction
| Females 4 6.3 0.36 (6.0-6.8) 5.68 1.42
{| Males 3 6.0 0.29 (5.8-6.3) A417 6.61 ns
_ Breadth at mastoids
| Females 4 18.2 0.48 (17.6-18.6) 2.64 <1.00
Males 3 18.3 0.44 (18.0-18.7) 2.07 6.61 ns
Length of rostrum
Females 4 17.6 0.91 (16.4-18.5) 5.19 < 1.00
Males 3 17.4 0.47 (17.0-17.8) 3.33 6.61 ns
Breadth of rostrum
Females 4 7.4 0.25 (7.2-7.8) 3.38 < 1.00
Males 3 led 0.12 (7.4-7.6) 1.33 6.61 ns
Alveolar length of maxillary toothrow
Females 4 8.9 0.34 (8.6-9.4) 3.82 < 1.00
Males 3 9.1 0.41 (8.8-9.5) 3.84 6.61 ns
Length of palatal bridge
Females 4 7.8 0.42 (7.5-8.4) 5.39 < 1.00
Males 3 ted 0.81 (6.8-8.2) 9.33 6.61 ns
Length of nasals
Females 4 eget 0.80 (16.3-18.2) 4.70 2.42
Males 3 17.9 0.35 (17.6-18.2) 1.68 6.61 ns
(with males being larger than females )
might convey a selective advantage.
However, the laboratory breeding cage
was clearly an unnatural situation. In
the natural environment, domination of
females by males may not be important
if females tolerate males only during
estrus but are willing to accept any male
at that time. Considering the habit of
solitary occupancy of dens and competi-
tion for den sites during times of high
population density (see Fitch and Rainey,
1956:517), females that are large enough
to protect choice dens for maternity pur-
poses may rear more young than less
robust females. On the other hand, most
adult male N. micropus collected in west-
ern Kansas in June, 1967, had what ap-
peared to be fresh wounds in the region
of the lower back, but no “battle scars”
were noted for females at that time (see
Fitch and Rainey, 1956:521, for similar
comments pertaining to N. floridana).
Perhaps in the natural environment,
physical competition and fighting is most
common between males, which would
cause selection for large size to be more
intense in males than females.
Brown (1968) and Brown and Lee
(1969) studied various physiological and
morphological responses of woodrats to
differing thermal regimes. It was found
that body size was related to tempera-
ture, and although no comparisons of
sexes were reported, it is clear that selec-
tive responses to temperature and other
environmental factors play a major role
in determination of size of woodrats.
Such factors probably act similarly on
animals of both sexes, tending to reduce
54 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
secondary sexual variation. The magni-
tude of secondary sexual variation prob-
ably is controlled by several interacting
forces, some of which favor secondary
sexual differences while others operate to
minimize such differences. The result is
as seen in Table 2; perceptible differences
exist, but these appear to be more pro-
nounced in some taxa (campestris, for
example) than in others (such as
baileyi).
Individual Variation
Of more than 2000 woodrats exam-
ined during this investigation, only five
had obviously atypical coloration that I
assumed to be genetically based. Three
of these, Neotoma micropus canescens
that were previously reported by Baker
(1956:286), are from near Sabinas,
Coahuila; all were collected on the same
day. One is a young adult female that
was lactating and the other two are
juveniles nearing completion of the post-
juvenal molt. Most hairs of the venter
are white to the base on all three, and
white hairs extend onto the sides and
lower rump. The female probably is the
mother of the two juveniles. The status
of the color pattern in the population
from which these specimens originated
would be of interest. The other two
abnormally colored specimens are Neo-
toma floridana attwateri. One (OSU
4541) is a young adult female from
northeastern Dewey County, Oklahoma;
dorsal coloration is a uniform creamy tan
and the ears are nearly white. The other
(KU 18682), from Anderson County,
Kansas, is an albino in fresh winter
pelage. The ears, plantar surfaces of the
feet, hair, and underlying skin are de-
void of pigment; written on the data
label are the words “eyes pink.”
A specimen of Neotoma micropus
obtained in western Kansas in June 1967
and another from Prowers County, Colo-
rado captured in April 1968 were dis-
tinctly reddish dorsally, at the time of
capture. Both were in old pelage and the
one from Colorado was still in reddish
pelage when sacrificed about six weeks
after capture. The other was molting at
the time of capture and eventually com-
pleted molt into a gray pelage lacking
the reddish coloration. This reddish
coloration is not considered to be ge-
netically based, but probably was the
result of chemical alterations of pigment
in old pelage and likely caused by ex-
trinsic factors such as high concentra-
tions of ammonia in the nest.
Because coefficients of variation re-
flect the ratio of the standard deviation
to the mean, the statistic is useful in
comparing the degree of variation be-
tween populations of a single species or
between populations of different taxa.
The coefficient of variation can be used
also to compare the relative reliability
of different measurements of a single
sample. Long (1968, 1969) recently sum-
marized patterns of individual variation
and comparative variation of measure-
ments commonly used in taxonomic in-
vestigations.
Coefficients of variation for each sex
of three samples of floridana and three
samples of micropus are shown in figure
9. The coefficients are superimposed on
Dice-grams illustrating the trends of vari-
ation among the measurements taken.
Size of all samples except the two (one
male, one female) for canescens from
Coahuila (M) are given in table 2. Sam-
ple M consisted of 12 females and 13
males. Length of tail vertebrae and
length of ear are the most variable di-
mensions considered, and also are two
of the four recorded from specimen
labels. Length of hind foot and _ total
length were recorded from specimen
labels. The former shows about average
variability, whereas total length is more
variable than all except one cranial mea-
surement, but less variable than lengths
of tail and ear.
Of the 10 cranial measurements,
length of the palatal bridge is the most
variable. This measurement varies in
part with the shape of the posterior mar-
gin of the palate (see beyond under
geographic variation of qualitative cra-
nial characters ), which is relatively vari-
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 55
i 2 § 12 Sra 8 3 3
gueey i 4 sus 10
)
= s
eo
E PD
eo
ie
s
wn
oO
o
28
10 ats 45 112 6
2
uu 1 Le 4 6 1 9
10 5 2
. Ss aS ESE + + 12
5.0 6.0 70 8.0 9.0
Coefficients of Variation
Fic. 9. Coefficients of variation for 14 external and cranial measurements showing variability of
that statistic in each. Measurements are as follows: A—total length; B—length of tail vertebrae;
C—length of hind foot; D—length of ear; E—greatest length of skull; F—condylobasilar length;
G—zygomatic breadth; H—least interorbital constriction; I—breadth at mastoids; J—length of ros-
trum; K—breadth of rostrum; L— alveolar length of maxillary toothrow; M—length of palatal bridge;
N—length of nasals. Numbers plotted on the horizontal lines are individual coefficients of variation
for each sample of adult woodrats, as defined below; odd numbers are males, and even numbers are
females (see figure 8 for geographic areas included within the coded localities indicated in paren-
theses): 1 and 2, Neotoma floridana baileyi (1); 3 and 4, N. f. campestris (2, 3, and 4); 5 and 6,
N. f. attwateri (5, 6, and 7); 7 and 8, N. micropus canescens (B and C); 9 and 10, N. m. canescens
(M); 11 and 12, N. m. micropus (P). The apex of the darkened triangle is the arithmetic mean of
the coefficients of variation of the 12 samples, and the thick horizontal bar is plus and minus two
standard errors of the mean; the thin horizontal bar is plus and minus one standard deviation of the
mean, and the horizontal line is the range.
able even at the intra populational level.
All cranial measurements were recorded
only to the nearest tenth of a millimeter
and length of palatal bridge is one of
the smaller dimensions; thus, the pre-
cision of data recorded relative to size
of the character measured would be only
about one-fifth of that for, say, greatest
length of skull. Least interorbital con-
striction was the next most variable cra-
nial measurement and also is one of the
smaller dimensions; however, other char-
acters measured having means of less
than 10 (alveolar length of maxillary
toothrow and breadth of rostrum) dem-
onstrate near average variability. Great-
est length of skull, condylobasilar length,
zygomatic breadth, and mastoid breadth
are the least variable characters mea-
sured; all having average coefficients of
variation less than 4.0.
To compare the relative variation of
the 14 characters simultaneously between
the 12 groups, three simple tallies were
made. When only extreme coefficients
were considered, one or the other of the
two samples of baileyi is least variable in
six of the 14 measurements and one or
the other of the samples of attwateri is
most variable in five instances. This tally
also shows that a sample of males is most
variable in 10 of the 14 characters con-
sidered. Each pair of samples from each
locality next was compared for all mea-
surements to determine if males were in
fact more highly variable than females.
Of the 84 comparisons (six localities
times 14 measurements ) made, males are
56 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
more variable than females in 49 in-
stances and less variable in 35, a differ-
ence not significant at P < 0.05 as tested
by Chi-square. Lastly, the coefficients of
variation for each character were as-
signed values on a rank-order basis so
that the lowest coefficient for a character
accrued one unit and the highest accrued
12 units to the respective taxa. These
scores then were totaled for each sample
by summing the 14 rank-order scores;
thus a low total implies less variation and
a high total more variation. As deter-
mined by this crude technique, the sam-
ple of baileyi females is least variable
(41.5) and the sample of campestris
males is most variable (134.0). Males
were shown to be more variable than
their female counterparts at four lo-
calities (N. m. micropus from locality P,
and N. m. canescens from combined lo-
calities B and C being the two excep-
tions); they have a rank-order total of
587 compared to 504 for females ( differ-
ent at P < 0.05, as tested by Chi square).
When scores of the sexes were summed
for each locality, the sample of baileyi
is least variable (106.5) and that of
attwateri is most variable (215.5). Coef-
ficients of variation in the sample of
micropus is intermediate (158.0) be-
tween baileyi and the four samples of
widely distributed taxa (201.5-215.5);
but in micropus the distribution of coef-
ficients is erratic, probably reflecting the
small sample size available.
The tendency for samples of males
to be more variable than those of females
is indicated by all three methods of anal-
ysis that I employed. Long (1969:298)
found males of domestic mammals more
variable than conspecific females, but
indicated that no basis presently exists
for attributing greater variation to males.
The apparent presence of relatively less
individual variation in the isolated sub-
species, baileyi, as compared to widely
distributed taxa is not surprising; small,
isolated populations are prone to loss of
variation by chance or “drift.” Addition-
ally, they lack one of the most important
means of acquiring “new” genetic varia-
tion, i.e. immigration. Mayr (1963:177)
suggested that a reasonable estimate of
“new genes normally acquired by a local
population through immigration is at
least 90 percent and possibly exceeds 99
percent.
It was expected a priori that individual
variation in the samples of campestris
would be more pronounced than in other
taxa. In part the prediction was correct;
the sample of campestris males is more
variable than other samples, but only
baileyi females and micropus males are
less variable than campestris females.
Possibly selection acting on populations
that live in similar environments main-
tains the observed degree of homogeneity
(Ehrlich and Raven, 1969), or perhaps
there is more interpopulational gene flow
in campestris than my observations have
indicated.
Variation Resulting from Captivity
The most striking differences ob-
served between a specimen that had
been reared, or at least maintained, in
the laboratory for an extended period of
time and one that had been killed at the
time of capture were in the teeth. The
cheekteeth of woodrats fed on laboratory
chow did not wear at a rate comparable
to that in natural populations. The molars
of cleaned skulls of laboratory rats often
are as much as a third or a half longer
than those of non-laboratory animals.
Furthermore, the reentrant angles of lab-
oratory-reared woodrats extend much
nearer to the alveolus than do those of
comparably aged non-laboratory rats. Al-
though this may be the result of reduced
tooth growth to compensate reduced
wear, the stimulus that stops or slows
growth is unknown. In some laboratory
specimens, alveolar tissue near the base
of the molars appeared reduced and
slightly porous. If the alveolar tissue of
laboratory rats grows abnormally slow or
if it is resorbed, the molar may undergo
normal growth but have higher crowns.
The incisors of woodrats living in the
laboratory frequently are broken, result-
ing in abnormal occlusion and the ab-
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 57
sence of wear on the opposing incisor.
The frequency of abnormal growth of
incisors is relatively high in laboratory
animals, whereas woodrats living in the
natural environment and having maloc-
cluding incisors probably are destined to
early death.
Comparisons of size of woodrats
reared in the laboratory with non-labora-
tory animals from the same geographic
areas are shown in table 3. Only speci-
mens at least 30 weeks of age that either
were born in the laboratory or were cap-
tured before they had completed the
postjuvenal molt were included in lab-
oratory samples. After specimens meet-
ing these criteria were separated by sex,
only three samples, Neotoma micropus
canescens (localities B and C) males and
females, and Neotoma floridana cam-
pestris (localities 3 and 4) females, con-
tained enough specimens (10 or more)
for conducting the tests. Non-laboratory
comparative samples included all avail-
able specimens of age groups VI, VII,
and VIII from the grouped localities in-
dicated above.
Differences in two measurements,
total length and alveolar length of maxil-
lary toothrow, are highly significant
(P <0.01) between the two samples of
N. f. campestris females; no highly sig-
nificant differences were observed for N.
m. canescens. Significant differences
(P <0.05) were observed for two other
characters (length of hind foot and
length of nasals) in floridana, one mea-
surement (total length) of micropus fe-
males, and five measurements (length of
hind foot, length of ear, greatest length
of skull, condylobasilar length, and
breadth of rostrum) for N. m. canescens
males. Total length of micropus females
is the only dimension significantly larger
in the non-laboratory or “wild” sample.
On the average, laboratory samples are
slightly larger in most measurements that
are not significantly different.
Increased size of laboratory animals
may be the result of a more nutritious
diet or it may reflect differences in age.
Many animals in the laboratory samples
were near two years of age. It is doubt-
ful that the average age of non-labora-
tory animals equals that of the laboratory
sample.
GEOGRAPHIC VARIATION
In the discussion beyond, I will in-
terpret patterns of both qualitative and
quantitative variation of morphological
characteristics primarily from an evolu-
tionary point of view in an attempt to
elucidate the relationships of woodrats.
If it can be determined whether patterns
of variation are concordant or discordant,
and clinal or abrupt, one can surmise
which patterns have resulted from pri-
mary intergradation, secondary intergra-
dation, or from present restrictions to
gene flow. Also, I will attempt to ascer-
tain if natural hybridization is introgres-
sive in N. floridana and N. micropus.
Pelage, Molt, and Color
Finley (1958:232) described the suc-
cession of molts and pelages of woodrats
as juvenal pelage, postjuvenal molt, sub-
adult pelage, second molt, first autumn
pelage, third molt, first winter pelage,
annual molt. My observations agree in a
general way with this scheme. Animals
born late in summer or early in autumn,
however, do not undergo the complete
sequence, but spend the first winter in
either the subadult pelage or first autumn
pelage.
Remarkably little published informa-
tion pertaining to molt in adult Neotoma
is available. Goldman (1910:12) sum-
marized his understanding of molt on
adults as follows: “The molting season
is somewhat irregular, especially in the
southern part of the range of the group.
The northern species molt once a year,
toward the end of summer or fall. The
southern forms usually molt in early
winter, but individuals in worn and in
fresh pelage may often be seen together.”
Linsdale and Tevis (1951:450-458) de-
scribed and discussed molt in Neotoma
fuscipes, and Finley (1958) studied it
in those species of woodrats that occur in
58 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
TABLE 3. Size comparisons of woodrats reared in the laboratory and those killed at the time
of initial capture (wild). Statistics given are sample size, mean, two standard errors of the
mean, range, coefficient of variation, Fs (F value calculated by single classification ANOVA),
and F (tabular F value at level of significance or at P<0.05 if not significant). One asterisk
and two asterices indicate significance at the 0.05 and 0.01 levels, respectively, whereas ns
indicates no significant difference.
Measurement F,
and treatment N Mean a= PND, Range (GW F
Neotoma floridana campestris females (Samples 3 and 4)
Total length
Wild 33 370.8 6.23 (340.0-409.0) 4,83 9.86
Laboratory 10 394.2 17.94 (331.0-421.0) 7.20 (gl
Length of tail vertebrae
Wild 30 154.9 3.59 (136.0-175.0) 6.66 3.70
Laboratory 10 162.7 8.93 (129.0-178.0) 8.68 4.07 ns
Length of hind foot
Wild 34 39.3 0.55 (36.0-42.0) 4.09 5.94
Laboratory 10 40.7 0.45 (39.0-43.0) 3.48 4.07 *
Length of ear
Wild 19 2.8 0.72 (25.0-32.0) 5.53 < 1.00
Laboratory 10 2.9 0.13 (24.0-31.0) 7.01 4.21 ns
Greatest length of skull
Wild 29 5.0 0.52 (47.0-53.3) DiS <1.00
Laboratory 12 5.0 il li/ (46.2-52.4) 4.05 4.10 ns
Condylobasilar length
Wild 26 48.2 0.56 (45.2-51.6) 2.97 2.83
Laboratory 12 49.1 0.99 (45.2-51.2) 3.49 4.11 ns
Zygomatic breadth
Wild oe 27.0 0.38 (25.1-29.6) 3.68 <1.00
Laboratory 12 27.2 0.63 (25.7-29.0) 4.03 4.11 ns
Least interorbital constriction
Wild oz 6.7 0.11 (6.1-7.5) 4.72, < 1.00
Laboratory 12 6.7 0.21 (6.2-7.5) oul 4.07 ns
Breadth at mastoids
Wild 29 19.4 0.24 (18.1-21.0) Sol <1.00
Laboratory 12 19.6 0.35 (18.5-20.5) Sale 4.10 ns
Length of rostrum
Wild 33 19.4 0.25 (i8=21)) 3.70 1.85
Laboratory 12 19.8 0.72 (17.4-21.2) 6.35 4.07 ns
Breadth of rostrum
Wild 32 8.5 0.12 (7.9-9.4) 3.85 1.34
Laboratory 11 8.6 0.25 (7.8-9.2) 4.81 4.08 ns
Alveolar length of maxillary toothrow
Wild 34 9.7 0.09 (9.1-10.3) 2.84 NPAT
Laboratory 12 10.0 0.09 (9.6-10.3) 1.61 ems
Length of palatal bridge
Wild 34 8.5 0.14 (7.8-9.4) 4.72 < 1.00
Laboratory 12 8.6 0.25 (8.2-9.6) 5.09 4.06 ns
Length of nasals
Wild 38} 19.2 0.26 (17.6-20.4) 3.93 5.30
Laboratory) 12 19.8 0.57 (18.0-21.1) 4.97 4.07 *
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 59
TABLE 3.
Continued.
Measurement F,;
and treatment N Mean == 2SE Range CV F
Neotoma micropus canescens females (Samples B and C)
Total length
Wild 31 355.8 5.97 (310.0-382.0) 4.67 4.47
Laboratory 11 351.8 11.25 (326.0-382.0) 5.30 4.08 *
Length of tail vertebrae
Wild 31 147.1 3.70 (130.0-165.0) 7.01 < 1.00
Laboratory iil 146.2 8.32 (126.0-171.0) 9.43 4.08 ns
Length of hind foot
Wild 30 38.4 0.54 (36.0-41.0) 3.85 2.90
Laboratory 13 39.2 0.69 (37.0-41.0) Bills 4.08 ns
Length of ear
Wild 24 27 0.56 (25.0-30.0) 5.10 4.00
Laboratory 13 28.1 0.86 (25.0-30.0) Bibs 4.l3)us
Greatest length of skull
Wild aT 48.8 0.70 (44.2-51.8) 3.75 <1.00
Laboratory 14 48.9 0.86 (46.2-51.4) Soll 4.10 ns
Condylobasilar length
Wild 29 47.0 0.58 (42.8-50.0) 3.34 < 1.00
Laboratory 15 47.4 0.71 (45.0-49.4) 2.92 4.07 ns
Zygomatic breadth
Wild 30 26.5 0.39 (24.7-29.1) 4.06 < 1.00
Laboratory 14 26.7 0.43 (25.2-30.0) 3.04 4.07 ns
Least interorbital constriction
Wild 32 6.3 0.11 (5.8-7.0) 4.72 2.80
Laboratory 15 6.2 0.15 (5.7-6.6) 4.73 4.06 ns
Breadth at mastoids
Wild HH if yal 0.23 (17.9-20.3) 3.10 Sea
Laboratory 14 19.4 0.17 (18.9-19.9) 1.65 4.08 ns
Length of rostrum
Wild 30 18.9 0.27 (17.2-20.2) 3.98 < 1.00
Laboratory 14 18.8 0.39 (17.8-20.2) 3.93 4.07 ns
Breadth of rostrum
Wild 32 8.3 0.14 (7.2-9.3) 4,92 < 1.00
Laboratory 15 8.4 0.21 (7.9-9.3) 4.87 4.06 ns
Alveolar length of maxillary toothrow
Wild 32 9.4 0.14 (8.5-10.1) 4,35 < 1.00
Laboratory 15 9.3 0.19 (8.4-9.9) 3.92 4.06 ns
Length of palatal bridge
Wild 31 8.0 0.19 (7.1-9.5) 6.56 < 1.00
Laboratory 15 8.0 0.18 (7.4-8.5) 4.38 4.06 ns
Length of nasals
Wild 30 19.2 0.35 (16.7-21.2) 5.04 < 1.00
Laboratory 14 19.4 0.43 (18.0-20.9) 4.15 4.07 ns
Neotoma micropus canescens males (Samples B and C)
Total length
Wild 23 370.1 9.46 (334.0-411.0) 6.13 PA
Laboratory 8 383.0 11.84 (354.0-398.0) 4.37 4.18 ns
60 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
TABLE 3.—Concluded.
Measurement Fs
and treatment N Mean as USD Range CV F
Length of tail vertebrae
Wild 23 152.6 5.10 (131.0-175.0) 8.01 < 1.00
Laboratory 8 154.8 (hey (142.0-172.0) 6.87 4.18 ns
Length of hind foot
Wild 5: 39.2 1.01 (35.0-45.0) 6.46 6.18
Laboratory 10 41.3 0.79 (39.0-43.0) 3.03 ANG
Length of ear
Wild 16 Weal 0.72 (25.0-29.0) 5.31 7.39
Laboratory 11 28.7 1.05 (27.0-32.0) 6.05 4.94 *
Greatest length of skull
Wild 25 49.5 0.63 (46.4-52.9) Bh ly 4.79
Laboratory 10 50.6 0.43 (49.4-51.9) 1.35 AL lis)
Condylobasilar length
Wild 24 48.3 0.66 (44.6-50.9) 3:08 5.24
Laboratory 10 49.5 0.44 (48.3-50.6) 1.39 ANS
Zygomatic breadth
Wild 26 26.7 0.36 (25.1-28.8) 3.47 < 1.00
Laboratory TR 26.9 0.39 (26.1-28.2) 2.42 4.13 ns
Least interorbital constriction
Wild Nil 6.3 0.11 (5.8-6.9) 4.39 < 1.00
Laboratory 11 6.4 0.13 (6.1-6.9) 3.38 4.11 ns
Breadth at mastoids
Wild 24 19.3 0.28 (18.0-20.8) 3.58 < 1.00
Laboratory ll 19,4 0.10 (19.2-19.8) 0.87 4.15 ns
Length of rostrum
Wild 26 19.4 0.28 (17.8-20.7) 3.67 < 1.00
Laboratory 10 19.5 0.40 (18.3-20.4) 3.23 4.13 ns
Breadth of rostrum
Wild 27 8.4 0.14 (7.5-9.2) 4.4] 4.86
Laboratory 11 8.6 0.22 (8.0-9.2) 0.22 ALL
Alveolar length of maxillary toothrow
Wild 27 9.3 0.12 (8.7-10.1) 3.47 2.19
Laboratory 11 9.5 0.22 (9.0-10.0) 3.81 411 ns
Length of palatal bridge
Wild 26 8.1 0.18 (6.8-8.9) 5.73 3.37
Laboratory 10 8.4 0.13 (7.9-8.6) 2.54 4.13 ns
Length of nasals
Wild 26 19.8 0.32 (18.0-21.1) 4.11 < 1.00
Laboratory 10 19.9 0.35 (19.0-20.7) 2.79 4.13 ns
Colorado. In both studies it was con-
cluded that only a single annual molt
occurs in adult woodrats.
Seasonal occurrence of molt in se-
lected samples of N. floridana and N.
micropus is shown in table 4. Specimens
of age-groups V-VIII were included in
these tabulations. With one exception,
animals were considered to be molting if
new pelage appeared to have been re-
placing old pelage regardless of whether
the replacement was symmetrical or in-
volved a complete replacement of hair.
Many woodrats have a varying number
of tiny spots of actively growing hair.
These probably are areas in which hair
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA
lost while fighting or in other ways not
directly associated with seasonal molt is
replaced. Specimens with such “spots”
that were not molting elsewhere were not
considered to be molting.
_ As can be seen in table 4, some wood-
rats obtained in every month were molt-
‘ing. It was thought that possibly only
animals of age-groups V and VI (which
still might have been in some stage of
maturational molt) were molting at
times other than late summer and au-
tumn as has been reported previously.
However, when only specimens of age-
groups VII and VIII were considered,
the seasonal array of molting and non-
molting individuals remained approxi-
mately the same.
In northern populations of the two
species studied, adults are almost invari-
ably in a dense, luxuriant winter pelage
by late November or early December.
Beginning in late winter or early spring,
the winter pelage of many individuals
begins to deteriorate; it becomes thinner,
less luxuriant, has many broken tips, and
appears “scruffy.” In other rats, the
)winter pelage seems to be well main-
/tained into late May or early June. When
the pelage begins to deteriorate, it gen-
erally is replaced erratically over the
body, usually beginning in those areas
where the winter pelage is thinnest or
61
most worn. This “molt” has little or no
symmetry of pattern. In occasional indi-
viduals, the winter pelage is nearly or
completely replaced by a shorter, usually
darker “summer” pelage. Some rats have
only localized spots of this pelage and
others show no sign of replacement until
July or August. At this time they appar-
ently begin the “annual molt” and molt
the old winter pelage directly into a new
winter pelage. Those individuals that re-
placed some or all of the pelage earlier
also molt into a new winter pelage in
late summer and autumn.
The molting sequence in southern
populations of both species is less clear.
Even the new winter pelage of southern
woodrats is shorter than “summer pelage”
of those from northern populations, and
the “annual molt” (molt into winter pel-
age) is only weakly synchronized among
animals of the same population. Usually
this molt occurs anytime from June to
October, and generally is complete by
November.
Whether one wishes to consider the
replacement of worn winter pelage prior
to the attainment of new winter pelage
as a “vernal molt” and the resultant pel-
age as a “summer pelage” is primarily a
question of semantics. Almost certainly
the only molt that is consistently com-
plete and common to all adults is the
TABLE 4. Seasonal distribution of molt in selected samples of Neotoma floridana and N.
micropus. See figure 8 for geographic areas included in coded localities.
Jan. Feb. Mar. April May June July Aug. Sept. Oct. Nov. Dec.
Sample 1 (Neotoma floridana baileyi)
Females
Molting = dat a = 0 = 1 2 = = = =
Examined __ : & 1 _— i 3 ae pi ae ses
Males
Molting = z ee es 1 S pases 2 si 2 BE as
Examined __ <= Ss — i om mat 2 28 2; = a
Samples 2, 3, and 4 (Neotoma floridana campestris)
Females
Molting re fe re 3 0 2, 2 2 5 2 1 0
Examined - tal 3 il 3 oe 3 5 38 2 9
Males
Molting <4 = 1 id 5 Z 1 3 c 0 1
Examined _ i = 5 z 1 3 E 2; To
62
MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
TABLE 4.—Concluded.
Jan. Feb. Mar. April May June July Aug. Sept. Oct. Nov. Dec
Samples 5, 6, and 7 (Neotoma floridana attwateri)
Females
Molting 0 5 2 1 js 1 1 1 6 1
Examined 2 Ta 12 2 : as 1 1 2 Tal 12
Males
Molting 0 1 0 0 sde i = 3 1 2 5 0
Examined 4 ®) 8 4 ne =a 3 1 2 9 6
Samples 8, 9, 10 (Neotoma floridana attwateri)
Females
Molting 2 0 2 7a i 0 ss 1 4 3 2
Examined 9 1 9} mah 3 1 sats 2 6 6 9
Males
Molting i 0 0 0 Sis 3 std 2a 5 3 1
Examined 8 9) 6 3 3 =a Pa 5 4 6
Samples 11 and 12 (Neotoma floridana attwateri)
Females
Molting 0 1 _ 0 2 5 3
Examined 3 1 ell, eee ed I 3 6 5
Males
Molting 1 0 Ad ae se Boe Ae 2 2 5 1
Examined 2, 2 a ae en aie a 2 3 5 2
Samples A, B, C, and F (Neotoma micropus canescens)
Females
Molting 0 0 il 8 3 i 2 2 0 =
Examined 2 i 1 10 i 6 9) 2 3
Males
Molting 1 1 0 0 3 2 6 fone 3 1 0
Examined = 1 1 1 1 5 4 6 ae 4 5 4
Samples D, G, H, and I (Neotoma micropus canescens)
Females
Molting 0 om 0 1 6 zs 1 3 0 0
Examined 2 es 1 3 us at 1 3 1 9
Males
Molting 0 0 a ees 3 2 a is pall rs 0
Examined 3 2 aes oe 3 6} ee EN fe tte 10
Samples J, K, L, and M (Neotoma micropus canescens)
Females
Molting 0 0 3 0 1 0 1 1 4 0
Examined 1 2 4 1 9) 1 2 i 12 i
Males
Molting 0 1 4 0 1 i = i = 10 *
Examined I 1 6 1 il 3 be i as 16 2
Samples N and P (Neotoma micropus micropus)
Females
Molting 0 2 1 1 2 hse 2 0
Examined a 4 4 1 1 2 10 ]
Males
Molting ) 3 2 2, 4 3 0
Examined 1 4 2 4 5 9 2)
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 63
autumn molt or in Finley’s (1958) ter-
minology, the annual molt. The “vernal
molt” apparently is primarily a mechan-
ism to maintain the pelage and may be
complete, abbreviated, or absent. For
‘many years it was thought that members
of the genus Peromyscus molted only
‘once a year (see Layne, 1968:141, for
review), but recent studies have shown
‘that at least in some species molting also
‘occurs at other times of the year ( Brown,
11963: Lawlor, 1965). Possibly the sea-
sonal molting regimes of members of the
two genera are similar, but characterized
y much more individual and geographic
ariation than previously has been
hought.
An attempt was made to correlate re-
roductive data from specimen labels
with molt in females. Pregnant or lactat-
ing females that were collected in spring
or early summer usually were in the old
winter pelage; however, pregnant and
lactating females collected in late sum-
mer often were actively molting. An
adult female N. f. campestris (KU
120844) was captured in December in a
relatively new winter pelage. She was
maintained in the laboratory until late
March without having been placed with
amale. At that time she was undergoing
what probably would have been a nearly
complete molt from her typical winter
pelage, which was in remarkably good
repair, to a new shorter darker “summer
pelage.” On 20 March she was placed
with a male and on 26 April she gave
birth to a litter. Insofar as I could deter-
mine, the molt had progressed very little
between those dates and remained with-
out change until she was killed on 10
June. The specimen shows no line of
“current” activity between the two pel-
ages, which are markedly different in
length, color, and general texture. Ap-
parently molt of woodrats is influenced
by the hormones of reproduction and
shortly after this female became preg-
nant the molt was arrested.
Other factors that probably influence
the timing and degree of completeness
of the “vernal molt” include age, condi-
tion of health, and condition of the ex-
isting pelage. Although exchange of pel-
ages clearly is necessary, especially in
northern woodrats preparing for winter,
molt may be one of the body processes
that is under a relatively loose genetic
control and easily altered when it is
physiologically advantageous for an in-
dividual to divert energy or reserves
elsewhere.
The variation in molts and pelages
of woodrats in spring and summer re-
sulted in some difficulty selecting speci-
mens for color measurements. Ideally,
only adults in fresh winter pelage would
be considered in analyses of geographic
variation in color. However, sufficient
samples from the various aggregate lo-
calities were not available when samples
were thus limited. It was necessary to
include all specimens whose pelage was
in relatively good repair, regardless of
season.
The effect of including animals col-
lected at different times of the year was
tested for each of the three reflectance
readings and for the total (value ob-
tained by summing the three individual
reflectance readings for each individual)
by pooling readings of animals from lo-
calities 5 through 11 (all Neotoma flori-
dana attwateri) and separating the indi-
viduals into four seasonal samples. Each
sample included animals killed during a
three-month period so that four samples
corresponding roughly to winter (De-
cember-February ), spring (March-May),
summer (June-August), and autumn
(September-November) were available.
Seasonal variation is not significantly dif-
ferent in reflectance of blue or green,
but is significantly different (0.05 > P >
0.01) for reflectance of red and for total
reflectance. These data were separated
by sex to test males against females.
Males were significantly paler (0.05 > P
> 0.01) as indicated by reflectance of
red, but F, values were less than unity
for blue and green, and less than F for
total reflectance.
Explanation of the slight seasonal
variation is commensurate with the above
64 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
discussion of molt and pelages. Most
woodrats are darkest in fresh winter pel-
age and palest in old pelage just before
undergoing molt into winter pelage,
which is the only more or less synchro-
nous molt of adults. This molt usually
occurs in September, October, or early
November; thus most animals in the au-
tumn sample recently had molted or
were molting. The high coefficients of
variation for this sample are attributable
to the fact that all specimens were not in
the same pelage. The three seasonal sam-
ples involving mostly animals in winter
pelage were not significantly different in
color, and even the sample composed
mostly of summer specimens was not sig-
nificantly different from the spring or
winter samples.
Specimens of both sexes and from
all seasons were pooled for each locality
for studies of geographic variation. Re-
sults of univariate analyses of intra-
specific color variation in Neotoma flori-
dana are shown in table 5. Highly
significant (P < 0.01) differences exist in
comparisons of group-means for all re-
flectance readings. In no case, however,
are animals from localities 5-13 (all sam-
ples of N. f. attwateri and the single
sample of N. f. rubida) significantly dif-
ferent from each other with respect to
color. Specimens from localities 12
(southern Texas), 6 (northeastern Kan-
sas), and 11 (northern Texas) tend to
be slightly paler in color than other spec-
imens. Samples 5 (north-central Kan-
sas), 10 (southeastern Oklahoma), and
13 (N. f. rubida) generally are darkest.
Within the subspecies N. f. campestris,
a rather clear trend exists from paler
animals in the west (localities 2 and 3)
to darker ones in the east (locality 4)
where the range of campestris meets that
of attwateri. In no case is the difference
between animals from localities 2 and 3
significant, but those from locality 4 are
significantly darker than those from 2 in
all reflectance readings. Specimens in
sample 4 also are significantly paler in
all readings from those of attwateri from
adjacent locality 5. Only in reflectance
of blue are differences between samples
3 and 4 shown to be significantly differ-
ent. The darker color of specimens from
locality 4 as compared to those in sam-
ples 2 and 3 probably has resulted from
intergradation with the darker attwateri
population to the east. With respect to
color, the zone of intergradation would
appear to have been assigned largely to
campestris, although in size (see be-
yond) animals from locality 5 are more
like those from locality 4 than from
locality 6.
Neotoma floridana baileyi (locality 1)
is paler than all samples of attwateri, and
significantly darker than campestris
(with the exception of the sample of
campestris from the narrow zone where
campestris intergrades with attwateri at
locality 4). The pale coloration of baileyi
is less tannish than that of campestris,
and although most specimens of baileyi
are distinctly paler than specimens of
attwateri, their coloration more closely
resembles that of attwateri, than that of
campestris. The habitat in which baileyi
occurs resembles that where attwateri is
found, but most adjacent habitat types
in northern Nebraska, which thus far
have not been found to support wood-
rats, are mostly shortgrass pasture (more
like the habitat of campestris). The pale
color seen in baileyi and campestris
probably signifies convergence, which
has resulted from adaptation to an arid
environment, from a darker common an-
cestor.
Table 6 contains results of univariate
analyses of intraspecific color variation
for Neotoma micropus. As opposed to
the pattern of color variation in floridana,
that in micropus is clearly clinal and
lacks noticeable steps. Specimens from
locality E (New Mexico) are paler on
the average than those from White Sands
National Monument (locality O, pre-
viously N. m. leucophea). Therefore,
there seems to be no sound reason for
recognizing the name leucophea. (If
larger samples separable by season had
been available, the White Sands popula-
tion might have averaged paler, but cer-
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 65
tainly the differences are slight.) When
all samples of micropus are considered,
specimens from localities in New Mexico
(E and O) and western Texas (F and J)
generally are palest in color as evinced
by higher reflectance readings.
Those from localities D, G, H, K, L,
N, and P generally are darker than those
from A, B, C, I, and M, which tend to be
intermediate. Darkest populations gen-
erally occur at localities in the eastern
parts of the range of the species, and
palest populations are from the more
arid western localities. As shown by the
TABLE 5. Geographic variation in color of selected samples of Neotoma floridana. F, was
calculated by single classification analysis of variance. Tabular F values are at the P<0.05
level of significance; ns indicates no significant difference within a group of means. Nonsig-
nificant subsets (as calculated by the Sums of Squares Simultaneous Testing Procedure) of
significantly different groups of means are shown in the last column. See figure 8 for geographic
areas included within each coded locality.
Color reflectance
measured, and His
coded localities N Mean + 2SE Range CV F SS-STP
Red
2 2 19.2 0.50 (19.0-19.5 ) 1.84 12.78 I
3 19 17.0 1.06 (13.0-20.5 ) 13.66 1.83 I
1 23 15.6 0.88 (12.0-20.0) 13.56 til
4 16 15.5 0.97 (12.0-19.5) 1252: ay Tne
12 16 14.1 0.92 (11.5-17.0) 12.96 Gemma
9 7 13.1 1.18 (12.0-16.5 ) 11.98 ee ok
6 12 13.0 0.85 (10.0-14.5 ) 133 Ie ll
TST il ONT 0.69 (11.5-14.0) Tells} if Jl
0 28 12.7 0.53 (10.0-17.0) 11.07 I
13 5 12.6 1.66 (10.5-15.0) 14.69 I
8 4 D5 0.82 (11.5-13.5) 6.53 I
10 5 12.2 0.93 (10.5-13.0) 8.50 I
5 6 ED 1.09 (10.0-13.5) 11.90 I
Blue
2 2 10.5 2.00 (9.5-11.5) 13.47 41.62 I
3 19 9.6 0.45 (7.5-11.5) 10.20 ESS I
4 16 8.3 0.42 (7.0-10.5 ) 9.96 I
1 23 8.0 0.32 (6.5-9.5 ) 9.61 I
12 16 6.6 0.28 (5.5-7.5) 8.49 I
5 6 6.5 0.52 (6.0-7.5) 9.73 I
11 ii 6.5 0.65 (5.5-8.0) 13/32 I
8 4 6.5 0.00 (6.5-6.5) 0.00 I
6 12 6.4 0.45 (5.0-7.5 ) Qa, I
9 1 6.3 0.37 (5.5-7.0) 7.76 I
7 28 6.0 0.19 (5.5-7.0) 8.41 I
13 5 5.6 0.37 (5.0-6.0) TAT I
10 5 Dro 0.75 (4.0-6.0) 15.79 I
Green
2 2, 12.0 2.00 (11.0-13.0) 11.79 39.62 I
3 19 10.5 0.52 (8.5-12.5) 10.85 1.83 | Lea
4 16 9.4 0.49 (8.0-11.5) 10.40 ae
1 23 8.3 0.28 (7.5-9.5) 8.10 MeL
6 102 les 0.40 (6.5-8.5 ) 9.35 IE JI
8 4 UP 0.65 (6.5-8.0) 8.90 iy, Ll
5 6 Mp2, 0.43 (6.5-8.0 ) E23 Ill
12 16 Ux 0.36 (6.0-9.0 ) 10.11 I
11 il UP 0.61 (6.5-9.0) PR22; I
a 28 6.9 0.20 (5.5-8.0) 7.65 I
9 1 6.9 0.29 (6.5-7.5) 5.51 I
13 5 6.5 0.32 (6.0-7.0) 5.44 I
10 5 6.2 0.68 (5.0-7.0) 12.23 I
66 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
TABLE 5.—Concluded.
Color reflectance
measured, and Firs
coded localities N Mean =+ 2SE Range CV F SS-STP
Total
2 2, 41.8 4.50 (39.5-44.0) 7.62 29.51
3 19 BH/all 1.90 (29.0-44.5 ) 11.19 1.83 I
4 16 33.2 1.66 (28.0-41.5) 9.96 oe
1 23 Sei, Lea (26.0-35.5 ) 9.14 eel
12 16 28.0 1.40 (23.0-33.5 ) 10.00 HI
6 12, 26.8 1.44 (2275=30)5)) 9.31 I
11 a 26.4 ei (23.5-31.0) 8.84 I
8 4 26.2 0.87 (25.5-27.5) 3.30 I
9 a 26.2 1.41 (24.0-30.0) 7.12 I
i 28 25.7 0.79 92,.0-31.5) 8.18 I
5 6 24.9 1.85 22,.5-29.0) 9.10 I
13 5 24.7 2.14: 22,.0-28.0) 9.67 I
10 5 VT 2.20 19.5-25.5) 10.40 I
sequence of means and arrangement of
maximal non-significant subsets in table
6, however, the trends in color variation
in N. micropus take the form of gradual
clines.
Qualitative Cranial Characters
Finley (1958:248-252) discussed sev-
eral cranial features of woodrats that
vary among taxa. Three cranial charac-
ters can be employed to distinguish skulls
of Neotoma angustipalata, N. floridana,
and N. micropus, although none is diag-
nostic. A fourth varies greatly with sex
and age but is useful in skull identifica-
tion. The three most useful characters,
the anterior palatal spine, the posterior
margin of the bony palate, and the
sphenopalatine vacuities (Fig. 10), are
discussed individually below and anal-
yzed geographically. The fourth, shape
of the interorbital region, was assessed
in the measurement of least interorbital
constriction. In micropus, the supraor-
bital region tends to be narrower and
more ridged than in floridana. Espe-
cially in mature micropus males (less
frequently in females ), ridging is so pro-
nounced that a structure resembling a
postorbital shelf is formed. In floridana
such a “shelf” is never present and the
interorbital region usually is nearly level.
Ridging between the orbits and presence
of the “shelf” generally are distinctive to
micropus, but because of variation with
sex and age, absence of these characters
is not distinctive to floridana. The num-
ber of adult N. angustipalata available
for analysis of normal variation in the
interorbital region is small; however,
specimens examined tend to be more like
micropus than floridana in this character.
Berry and Searle (1963) discussed
occurrence and frequency in several
rodent species of characters similar to
the three considered below. Hedges
(1969) studied such characters inter-
specifically and geographically in two
species of Apodemus. These authors, and
others, referred to such characters as
“epigenetic characters.” Berry and Searle
(1963:607) stated that “many genes are
concerned in the determination of each
character, while environmental factors
are also very important, so that the ef-
fects of individual genes cannot be iso-
lated.” I am not presently prepared to
comment on the relative genetic versus
environmental control of the germane
characters, but planned study of these
through several generations of labora-
tory-bred woodrats should be elucidat-
ing. Although the term “epigenetic” may
well apply to characters such as these,
I prefer to avoid use of the term until
more is known about their developmental
control and functional importance. How-
ever, “qualitative characters” is also
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 67
TABLE 6. Geographic variation in color of selected samples of Neotoma micropus. Fs; was
calculated by single classification analysis of variance. Tabular F values are at the P<0.05
level of significance; ns indicates no significant difference within a group of means. Non-
significant subsets (as calculated by the Sums of Squares Simultaneous Testing Procedure) of
significantly different groups of means are shown in the last column. See figure 8 for geographic
areas included within each coded locality.
Color reflectance
measured, and F,
coded localities N Mean + 2SE Range CV F SS-STP
Red
E 5 yall 0.97 (16.5-19.0) 6.34 5.44 I
O 2 16.8 0.50 (16.5-17.0) 2.11 V6 II
J 3) 16.8 2.50 (15.5-18.0) 10.55 en
F 2 16.8 0.50 (16.5-17.0) 2 Aa if ah 1
B 18 16.2 0.98 (13.0-19.5) 12.87 It 1k
C 17 15.6 0.88 (13.5-19.5) 11.56 Vit
M 32 15.1 0.78 (10.5-20.5 ) 14.69 1h J fai
A 5 14.9 0.73 (14.0-16.0 ) 5.51 oe It wt
I 3 14.5 0.58 (14.0-15.0) 3.45 ele teon
G 2 14.2 2.50 (13.0-15.5) 12.41 If Je Wt VE
H 18 13.9 0.72 (5 = 17.0) 10.94 Ie Te I
L 3 13.7 2.40 (12.0-16.0) 15.18 Je al
12) 10 13.4 1.09 (11.5-17.0) 12.81 If lt
N 23 Sal 0.66 (11.0-16.5) eds I
D 12 Ls! 0.81 (10.0-14.5) 10.79 I
K 13 13.0 1.08 (8.5-15.5) 14.97 I
Blue
F 2 ORD, 3.50 (10.5-14.0) 20.20 AKG: I
E 5 10.5 1.18 (9.0-12.5) 12.60 1.76 ie
O 2 10.2 1.50 (9.5-11.0) 10.35 II
J 2 100 2.00 (9.0-11.0) 14.14 ie
B 18 10.0 0.56 (8.0-12.5) 11.88 1
C yy 9.4 0.42 (8.0-11.0) 9.2) IE JEU
A 5 9.1 0.66 (8.0-10.0) 8.15 if Ae I
M 32 8.9 0.52 (7.0-13.0) 16.69 i it i
I 3 8.8 0.67 (8.5-9.5) 6.54 it
G 2 8.2 1.50 (7.5-9.0 ) 12.86 eae It al
H 18 8.2 0.42 (7.0-10.0) 10.88 It Jt dt
D 12 7.9 0.46 (7.0-9.5) 10.02 1G It
L 3 7.5 1.00 (7.0-8.5) E55 WAT
K 13 eo 0.56 (5.0-9.0) 13.84 Tek
N 23 eS 0.34 (6.0-9.5 ) 11.26 I
P 10 6.8 0.44 (5.5-7.5) 10.35 I
Green
F » 15.0 1.00 (14.5-15.5) 4.71 11.44 I
J 2 12.8 7.50 (9.0-16.5) 41.59 1.76 ey
E 5 10.7 ONT (9.5-13.0) 12.63 eter
B 18 10.4 0.68 (8.5-13.5) 13.83 leer
O ® 10.0 1.00 (9.5-10.5) 7.07 ee a
Cc 17 9.6 0.44 (8.0-11.0) 9.41 Ie Ut We Te at
A 5 9.5 0.63 (8.5-10.5) 7.44 ME Te
M 32 9.2 0.57 (6.5-13.5) 17.45 IL JG a Wh I
H 18 8.7 0.47 (7.0-11.0) 11.53 ML ee a a
G 2 8.5 1.00 (8.0-9.0 ) 8.32 Teele Vest
I 3 8.5 1.00 (8.0-9.5) 10.19 We A
L 3 8.3 1.20 (7.5-9.5) 12.49 Me a
D 12 8.2 0.57 (7.0-10.5 ) 12.06 eel
K 13 Hell 0.60 (5.5-9.5 ) 14.18 lial
N 3} 7.6 0.35 (6.0-9.5 ) 10.86 I
1p 10 Ue 0.58 (6.0-8.5 ) 12.76 I
68 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
TABLE 6—Concluded.
Color reflectance
measured, and F;
coded localities N Mean + 2SE Range CV F SS-STP
Total
F 2 44.0 2.00 (43.0-45.0 ) PAL 8.93 I
J 2, 39.5 12.00 (33.5-45.5 ) 21.48 1.76 II
E 5 38.3 3.20 (35.5-44.5 ) 9.35 I ll
O 2 37.0 3.00 (35.5-38.5 ) 5.73 It it 3
B 18 36.0 PAPAL (27.5-43.5 ) 13.03 Mh Jt I
Cc 17 34.6 1.53 (29.5-40.5 ) 9.11 ETL A
A 5 3o.0 1.70 (30.5-35.5 ) 5.68 1G Ct 3
M 32 Soul: Wee (24.5-46.5 ) Way ils} YL Wu
I 3 31.8 E33} (30.5-32.5 ) 3.63 Ie Ie i
G 2, 31.0 5.00 (28.5-33.5) 11.40 ye I ae
H 18 30.8 1.47 (26.5-36.5 ) 10.10 oe Ie
1G; 3 29.5 1.53 (28.0-30.5 ) 4,48 it at dt
D 12 29.2 1.67 (25.0-34.5 ) 9.92 ML gl
N 2S 28.0 ore, (24.0-34.0) 10.41 II
K lis} 28.0 2.16 (19.0-33.5 ) 13.90 I
12 10 Hao) 1.74 (23.5-33.0) 10.00 I
somewhat of a misnomer because the
variation is nearly continuous and, as —
y noted by Berry and Searle (loc. cit.),
must be treated by statistics rather than
Mendelian methods.
Another important characteristic of
woodrat skulls involves the relative de-
velopment of the vomer within the narial
passage and the resultant absence or
presence and relative size of a maxillovo-
merine notch (Finley, 1958:249). In
four species of Neotoma, the three dis-
cussed herein and N. palatina (Hall and
Genoways, 1970), the vomerine septum
is solid anterior to the palate (see also
Anderson, 1969:47, Fig. 7). None of the
specimens of N. angustipalata, N. flori-
dana, or N. micropus from the Central
Ces Plains examined by me exhibit a maxil-
lovomerine notch, but all specimens of
N. f. magister in the Museum of Natural
History of The University of Kansas have
Fic. 10. Semidiagrammatic drawing of a
skull of Neotoma floridana showing: A—ante-
rior palatal spine; B—posterior margin of the
bony palate; and C—sphenopalatine vacuities.
Enlargements of A-C (scale at bottom applies
to all) to the right illustrate the range of vari-
ation seen in these characters in N. floridana and
N. micropus. Numbers represent sequential
scoring values assigned to each character. KU
numbers of skulls from which enlargements
were drawn are: A—(1) 53908, (2) 3094,
(3) 117335, (4) 117325, (5) 119707; B—(1)
119615, (2) 117786, (3) 117783, (4) 117324,
(5) 119797, (6) 119796, (7) 119804, (8)
53906; C—(1) 16111, (2) 117774, (3) 117786,
(4) 117324, (5) 119804, (6) 38922.
a deep notch and also lack a fork on the
anterior palatal spine discussed below
(but see Schwartz and Odum, 1957).
Anterior Palatal Spine-—Geographic
variation in the morphology of the an-
terior palatal spine is shown graphically
in figure 11 and in percent frequency of
occurrence of the five categories (Fig.
10) in table 7. Calculations for making
the pie diagrams (Fig. 11) were as fol-
low: 1) the percent frequency of each
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 69
category was multiplied by the score
shown (Table 7) for that category; 2)
these values were summed for each
grouped locality; 3) the lowest total was
subtracted from each total; and 4) this
value then was divided by the largest
remaining value and converted to per
cent development of the fork relative to
the sample having the largest fork. This
percentage value is represented by the
darkened areas in the symbols of figure
11. Thus, circles that are most darkened
represent samples having a greater fre-
quency of occurrence and larger size of
the fork on the palatal spine than samples
from localities with more open circles.
Morphology of the anterior palatal
spine varies geographically in both N.
floridana and N. micropus. In N. f.
baileyi, the bifurcate condition is ob-
served in more than 91 percent of the
specimens examined and in more than
40 percent of these the spine is classified
as “large.” As a result, baileyi represents
100 percent development for this charac-
ter and the percent development for all
other samples is relative to this situation
in baileyi. Of the two specimens of N.
m. canescens from White Sands National
Monument, New Mexico (locality O,
previously N. m. leucophea), examined
for this character, neither has a fork;
thus, that sample represents zero percent
relative to the condition seen in baileyi.
TABLE 7. Percent frequency of occurrence of five morphological categories of the anterior
palatal spine in 31 grouped samples of Neotoma floridana, N. micropus, and N. angustipalata.
See figure 10 for illustrations of morphological categories and figure 8 for geographic areas
included within each coded locality.
Spatu- Small Medium Large
Locality Pointed late fork fork fork
code N (1) (2) (3) (4) (5)
1 49 8.16 8.16 40.82 42,86
2, 43 9.30 = 55.82 25.58 9.30
3 79 10.13 5.06 48.10 26.58 10.13
4 69 8.70 11.60 Bo00 31.88 14.49
5 12 4 =e 58.33 33.34 8.33
6 67 13.43 4,48 55S 19.40 7.46
i 63 SLAM Take aL 34.92 31.75 ILA
8 73 24.66 4.11 41.09 17.81 12.33
9 93 6.45 13.98 47.31 32.26
10 63 17.46 2a 28.57 33.33 20.64
J ON 14.82 14.82 33.33 33.33 3.70
12 50 38.00 6.00 46.00 8.00 2.00
13 17 41.18 5.88 47.06 uae 5.88
A Bi7/ 97.30 Sls 2.70 —_ aes
B 98 76.53 Wala 16.33 e
Cc iLaly/ 94.02 lecal 3.42 0.85 =e
D 69 92.75 1.45 4.35 ce. 1.45
E 23 82.61 4.35 13.04 oe at
F 55 89.09 1.82 9.09 a we
G 37 89.19 = 10.81 sie ETA
H 43 86.05 = 13.95 an Es
I 108 89.81 1.85 5.56 2.78
J 45 95.56 4,44 pase a:
K 3D 94.28 we 2.86 2.86
I, 50 94.00 2.00 4.00 we ate
M Al 73.24 8.45 18.31 ate =
N 44 86.36 = 13.64
O 2 100.00 = —s fue a
12 16 87.50 6.25 Fe 6.25
Q 1 BZ x 100.00 ts
R 9 DPA ON) 2222, 44.45 Wt AL et
S 55 60.00 3.64 23.64 5.45 UU
70 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
Only one sample of N. micropus (N.
m. planiceps, locality Q) demonstrates
a higher percentage than some samples
of N. floridana. Because planiceps is
known only by the holotype, which has
a small fork on the spine, this sample is
not necessarily indicative of the condi-
tion in the population. With the excep-
tion of planiceps, however, percent
morphological development of the fork
in micropus is consistently below 15, and
populations geographically adjacent to
floridana show no apparent increase
either in the frequency of occurrence of
a fork or in size of the fork as compared
to those not geographically adjacent to
floridana. A fork classified “large” is
seen only in one specimen of micropus
(KU 69604), but five other specimens
from the same _ locality (Comanche
County, Kansas) do not have forked
spines. Medium-sized forks are uncom-
mon in micropus, but all samples repre-
- > oS 7
108 96 |
| ip ae iT a) |
| eo . |
! = | \
lite. 4 }
2p | | © |
es eS ts ee --- \ 432|
24--
| i eS a
108 ; a : AR
Fic. 11. Geographic variation in morphol-
ogy of anterior palatal spine in three species ot
Neotoma. See figure 8 for geographic areas
represented by each symbol and text for discus-
sion of variation and calculations
sented by more than 16 specimens have
at least one individual with a bifurcated
palatal spine. Grouping of samples was
not conducive to demonstrating local
populational variation; only one series of
specimens from a single locality deviates
noticeably in frequency of the palatal
spine as compared to that of other speci-
mens from the aggregate locality. Six
of seven micropus (MHP 3377-81, 4634-
35) collected on the same date from 3
mi S and 14 mi W Johnson, Stanton Co.,
Kansas, have small terminal forks on the
anterior palatal spine. Two of five ani-
mals from other localities in Stanton
County also have small forks. Therefore,
although less than 10 percent of the
other specimens from locality B have
forked spines, 66.7 percent of those from
Stanton County demonstrate the char-
acter.
Considering intraspecific variation in
Neotoma_ floridana, samples of both
campestris and attwateri from Colorado
and Kansas are similar, ranging from
near 65 percent to 80 percent develop-
ment. Of the three samples from Okla-
homa, specimens from locality 10 (south-
eastern part of the state) have an aver-
age similar to that of samples of floridana
from Kansas. Frequency of the fork is
noticeably lower in specimens from lo-
cality 8, and even when present the forks
tend to be relatively smaller. Many of
the specimens in this sample originated
from Blaine, Dewey, and Major counties,
Oklahoma, all of which are near the
known area of sympatry and_ natural
hybridization of floridana with micropus.
It should be reiterated that specimens
from the locality of sympatry were not
pooled with those from adjacent locali-
ties, but were treated separately as a
single sample (S). The intermediacy of
this sample is evident in figure 11.
Intermediacy of sample S was ex-
pected. If considered alone, the ten-
dency toward intermediacy in sample 8
might lead to the conclusion that hy-
bridization of the two species in central
Oklahoma is introgressive. This observa-
tion must not be disregarded in evalua-
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA ae
tion of the specific integrity of floridana
and micropus. The importance of the
reduced frequency and size of forks on
the anterior palatal spine of specimens
from sample 8 may be even more sig-
nificant when considered in view of the
high frequency of the fork on specimens
from adjacent sample 9. When only spec-
imens from Oklahoman localities 8 and
9 and the two adjacent localities for
micropus (G and H) are considered,
those from locality § appear almost per-
fectly intermediate. If these findings are
interpreted as being the result of intro-
gression, the flow of genetic materials
then would appear to be eastward and
not westward. However, Key (1968:19)
has shown that in some instances hybrid
suture zones are in a manner analogous
to semipermeable membranes. If so, they
probably allow flow of some genes in
only one direction, others in the opposite
direction, and still others to move in
both directions. Lewontin and Birch
(1966) have hypothesized, with support-
ing evidence, that a species may actually
become better fit to expand its distribu-
tion as a result of having introgressed
certain desirable genes from a closely
related species. In neither case discussed
did the original hybridizing taxa merge
to form a single species.
Samples of floridana from Texas dem-
onstrate the lowest percent scores of sam-
ples of that species. The sample of N. f.
rubida (locality 13) shows least develop-
ment of the spine and is not geograph-
ically adjacent to a population of micro-
pus. Localities 11 and 12, however, are
geographically adjacent to the range of
micropus and the reduction in frequency
and development of the fork in these
populations could be interpreted as dis-
cussed above for specimens from locality
8. On the other hand, sample 8 and the
Texas samples may represent no more
than a geographic cline toward reduc-
tion and loss of the fork. Further inter-
pretation must await additional material
from Oklahoma and Texas as well as
study of this character in eastern popula-
tions of floridana.
Morphology of the anterior palatal
spine in N. angustipalata is highly vari-
able (see Hooper, 1953:9-10, for notes
on apparent excessive variation within
this species), but is more similar to flori-
dana than micropus. The presence of a
small fork and the deep reentrant angle
of MI on the holotype of N. m. planiceps
(both characters unlike typical micropus
and resembling angustipalata) support
my earlier suggestion that rats of these
two nominal taxa may actually represent
a single taxon. Additional specimens of
angustipalata from localities in northern
San Luis Potosi and more planiceps from
near Rio Verde should elucidate this
question.
Because the anterior palatal spines of
other species of Neotoma are not forked
(Finley, 1958:252, reported the presence
of a fork on one specimen of N. albigula),
it seems logical to assume that the forked
condition is derived, and that a pointed
spine represents the original or “primi-
tive’ grade. A solid vomer is also the
exception rather than the rule for Neo-
toma. Both characters apparently
evolved together in the precursor of the
angustipalata-floridana-micropus — com-
plex. Subsequently, evolution either has
favored the solid vomer equally in all
three species or the character was al-
ready “fixed” before speciation within
the complex occurred. In the case of the
forked spine, it appears that at least some
members of the precursory species must
have possessed the character but selec-
tion has favored it more strongly in
floridana and angustipalata than in mi-
cropus. Alternatively, the frequency of
occurrence may have been dispropor-
tionately in favor of the direct ancestors
of angustipalata and floridana at the
time of isolation.
Posterior Margin of Bony Palate.—
Calculations of percent development of
the posterior margin of the palate were
conducted in a manner similar to those
described for the palatal spine. Deter-
mination of sequence for scoring varia-
tion in the posterior margin of the palate
was more difficult. On the palate, the
72 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
plain or rounded condition of the palatal
margin probably is intermediate ( primi-
tive?) with the deep notch being one
extreme (advanced?) and the large con-
vexity being the other (also advanced? ).
The decision concerning which extreme
to designate one and which to designate
eight was arbitrary and does not imply
evolutionary direction. Less arbitrary
and more troublesome was the decision
of scoring condition four (Fig. 10), in
which two convexities form a median
notch. Variation in morphology of the
margin results from the manner in which
the right and left halves of the develop-
ing hard palate adjoin. When a single
projection is present, approximately half
of the bone involved was contributed by
each side of the palate. Conversely,
when an indentation is present, it is be-
cause the two halves of the palate fuse
anterior to the posterior margin. When
two projections are present, each con-
sists only of bone originating from a
single half of the palate; the resultant
“notch” between the projections clearly
is homologous with the notch present in
the absence of projections. Thus, two
projections are homologous to the single
projection characteristic of other animals.
Because most (if not all) other species of
woodrats tend to have either a rounded
palatal margin or one with a convexity,
is is most parsimonious to conclude that
the notch is derived and that the double
projection is an evolutionary grade in
N. f. baileyi. It may be a condition
derived from the single notch seen fre-
quently in N. floridana. If the latter is
the case, this condition probably should
have been scored as one and placed at
the left of the series. In any event, it
apparently is more closely allied to the
indentation than to the single convexity,
and therefore, was scored as intermediate
between the rounded margin and the
smallest indentation.
On the average, the sample of Neo-
toma micropus canescens (locality E)
from New Maxico exhibited greatest de-
velopment of the posterior palatal con-
vexity. Nearly 75 percent of specimens
in that sample have convexities classified
as medium or large. Therefore, this sam-
ple was established as 100 percent de-
velopment of the palatal convexity. The
palatal margins of specimens of N. f.
rubida (locality 13) show the least ten-
dency toward a convexity, with 11 of 12
specimens having an indentation and
none having a convexity. Thus, sample
13 is considered zero percent relative to
sample E for this character (see Table
8, and Fig. 12).
Geographic variation in the morphol-
ogy of the posterior margin of the bony
palate in micropus is slight, ranging from
the established 100 percent in sample E
to 75.9 percent for sample G. Intra-
specific variation in floridana is greater
than for micropus, ranging from the es-
tablished zero percent at locality 13 to
53.7 percent at locality 5. In most sam-
ples of floridana, percent development of
a convexity is between 10 and 30, but in
three samples (1, 5, and 11) it exceeds
40 percent. In sample 1 (baileyi), the
high frequency (49 percent) of the
double convex palatal margin discussed
above accounts for the high index of de-
velopment, but in samples 5 and 11, the
frequency of this morph is not especially
high. Both of these populations are char-
acterized by a relatively high incidence
of animals with rounded palatal margins.
Rounded margins are common in labo-
ratory hybrids having a floridana parent
with an indentation and a micropus par-
ent with a convexity. Locality 5, al-
though adjacent in the broad sense to
localities C and D, is situated geograph-
ically so that woodrats from there are
not currently in contact with any popula-
tion of micropus. If the two species oc-
curred together in the vicinity of the
Arkansas River at some date in the past
(prior to settlement of the area by Euro-
pean man), it seems plausible that the
intermediacy of population 5 could be
the result of previous hybridization be-
tween the two species. However, speci-
mens from locality 5 demonstrate no
morphological or other proclivities to-
ward micropus in other characters, and
re)
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74 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
the sample is relatively small (13 indi-
viduals). Probably it is best not to
attribute the deviation seen in this pop-
ulation to past or present hybridization,
but rather to interpret it either as a local
population phenomenon or an artifact of
the small sample.
Interpretation of palatal morphology
in sample 11 is more difficult and may
represent one result of hybridization of
floridana and micropus in north-central
Texas. Specimens of this sample also
tend toward micropus with respect to
the anterior palatal spine discussed
above. As mentioned elsewhere, a sam-
ple of floridana from southwest of Dallas,
Texas, was nearly intermediate in color
between the two species (see beyond
under discussion of results of discrim-
inant function analysis ). Specimens from
locality 8, which show a marked _ ten-
dency toward micropus in morphology
40 : Sa
= : > \ &s oo ta
' J
& A ©;
hae ES eee \
| a . aera |
24\- { @: 1
| | o sO 150
Fic. 12. Geographic variation in morphol-
ogy of the posterior margin of the bony palate
in three species of Neotoma. See figure 8 for
geographic areas represented by each symbol
and text for discussion of variation and calcu-
lations.
of the anterior palatal spine, do not differ
notiecably in morphology of the posterior
palatal margin from specimens from lo-
calities remote from the range of mi-
cropus. Specimens from the locality of
sympatry (sample S) are approximately
intermediate between the adjacent pop-
ulations of the two species in average
morphology, but demonstrate a range of
variation from medium indentations to
large convexities. Increased variation in
a hybrid population is, of course, to be
expected. With respect to this character,
specimens of the species angustipalata
are more like micropus than floridana.
Sphenopalatine Vacuities—Variation
in form and size of the sphenopalatine
vacuities was scored and treated in a
manner similar to that explained pre-
viously. The range of observed variation
and values assigned to each category are |
shown in figure 10; percent frequency of
each category for each sample is shown
in table 9, and the relative size of the
vacuities for each population is shown
geographically in figure 13. On the aver-
age, vacuities in specimens from locality |
G are largest. That sample was set as_
the standard of 100 percent development.
Vacuities of specimens from locality 4
are smallest on the average, and were set
at zero percent relative to the vacuities
of animals from sample G.
The average size of the sphenopala-
tine vacuities is markedly different in
samples of micropus as compared to that
of floridana; samples of the former range
from 60.3 percent (N. m. planiceps) to
100 percent (sample G), whereas those
of floridana range from zero percent (lo-
cality 4) to 50.6 percent for sample 1
(N. f. baileyi). Neotoma angustipalata is
highly variable with respect to morphol-
ogy of the vacuities; it is clearly flori-
dana-like when averages are considered.
Specimens from the locality of sympatry
(sample S) are intermediate (58.6 per-
cent), but on the average nearer micro-
pus than floridana.
Size of the sphenopalatine vacuities
in specimens of baileyi is appreciably
larger on the average than those of other
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 75
TABLE 9. Percent frequency of occurrence of six morphological categories of the spheno-
palatine vacuities in 31 grouped samples of Neotoma floridana, N. micropus, and N. angusti-
palata. See figure 10 for illustrations of morphological categories and figure 8 for geographic
areas included within each coded locality.
Very
Locality Closed Minute Small Medium Large large
code N @t) (2) (3) (4) (5) (6)
1 47 = am 44.68 38.30 17.02
2, 38 ae 23.68 44.74 23.68 7.90
3 63 =e 23.81 55.56 15.87 4.76
4 44 oe Tue 27.27 ee
5 12 —_ 2.5.00 66.67 8.33
6 59 1.70 22.03 67.80 8.47
7 56 1.79 41.07 51.78 5.36
8 27 = 18.52 59.26 DIDO,
9 13 = 15.38 84.62 =
10 1 = 8.33 75.00 16.67
11 16 sth 2.5.00 75.00 ae
12 4] am? 36.58 53.66 9.76
13 ify 8.33 33.33 41.67 16.67 = aut
A 34 ae, aed 5.88 44.12 41.18 8.82
B 87 aL a2 2.30 29.88 66.67 PS
C 78 — = 1.28 12.82 79.49 6.41
D 43 Be oS 2.33 41.86 43.48 230
E 14 a fat 14.29 50.00 28.57 7.14
F 16 ee a5 12.50 56.25 lb is
G 14 ae eee ae 21.43 42.86 Soe
H 30 _— ae: 10.00 23°35 63.34 3.33
I 2 =ae exh = 50.00 50.00 bea
J 18 Ps mate 5.56 50.00 38.88 5.56
K 19 = a = 36.84 42.11 21.05
IG, 10 «<< ”? . . . . .
Sl” and “S2” represent samples of micropus-like and floridana-like woodrats, respectively, from
the same locality; “6 X D” is a sample of laboratory bred F; hybrids whose parents were from
localities 6 and D.
78 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
The bacula of four adult F, hybrids
between micropus from locality D and
floridana from locality 6 also were mea-
sured, averaged, and plotted in the dia-
gram. This sample was plotted in a posi-
tion nearly intermediate between the
parental populations, but more like flori-
dana if all localities are considered. The
intermediacy in the bacula of hybrids
demonstrates the assumed genetic basis
for determination of the shape of the
bone.
Because woodrats from the locality
of sympatry, 3 mi S Chester, Major Co.,
Oklahoma, were identified by charac-
ters of the skin and skull, but not the
baculum, the three specimens most like
floridana (S1) were averaged indepen-
dently from the five most like micropus
(S2). When plotted as above, the S1
sample appears to be typical of floridana
and gives no indication of effects of hy-
bridization. Sample S2 plots in a posi-
tion marginal to other samples of mi-
cropus, but clearly more like micropus
than floridana. Bacular measurements of
woodrats from other localities do not
indicate any obvious intraspecific or geo-
graphic trends nor do they seem to be
noticeably correlated to any of the other
measurements and characters studied. In
most instances the baculum of floridana
can be distinguished from that of micro-
pus or angustipalata, but no completely
diagnostic differences exist in the mor-
phology or size of the bone.
Univariate Analyses of Mensural
Characters
The four external and ten cranial
measurements described previously were
analyzed by Powers’ UNIVAR Program
in univariate assessment of geographic
variation. This was done separately for
each sex and each species, then sepa-
rately for each sex with samples of both
species treated simultaneously. These re-
sults are discussed below, in a considera-
tion of general trends of geographic vari-
ation. A more detailed evaluation that
includes discussion of each measurement
and subset relationships of group-means
as determined by SS-STP (as included
exemplarily below for total length) may
be found elsewhere (Birney, 1970).
Neotoma floridana.—Standard statis-
tics computed on measurements of spec-
imens from the 13 pooled localities of
Neotoma floridana are shown in table 10.
Interlocality variation in the measure-
ments of total length is significantly
(P <0.01) different for both sexes. For
males, localities are separated into two
broadly overlapping, non-significant sub-
sets (hereafter called subsets) indicating
that animals from southeastern Texas (N.
f. rubida, locality 13) and from south-
eastern Kansas (locality 7) are signifi-
cantly larger than those from localities
6 (northeastern Kansas) and 9 (north-
eastern Oklahoma). Males from locality
12 (southern Texas), adjacent on the
west to locality 13, also are large. Males
from sample 7 are significantly larger
than those from both adjacent localities
(6 and 9), but not significantly larger
than those from non-adjacent localities.
In females, variation in total length is
similar to that for males, but group-
means separated into five subjects with
females from locality 5 being. signifi-
cantly larger than those from localities
8, 6, 10, and 9 (hereafter written as
locality 5 > 8, 6, 10, 9), locality 13 > 6,
10, 9 and locality 12 >9. The only ad-
jacent localities showing significant dif-
ferences are 5 and 6, the two samples
from north-central and northeastern
Kansas.
Hind foot length in both sexes is
greatest in N. f. campestris and the sam-
ple of N. f. attwateri (5) that is geo-
graphically contiguous with campestris.
Ear length is not significantly different
for group-means in either sex. Coeffi-
cients of variation for external measure-
ments are high compared to those for
cranial measurements. Although analy-
ses of these characters are indicative of
total size relationships, they probably
are less reliable than analyses of cranial
dimensions. Differences that may ac-
tually exist in external size are difficult
to document statistically because unre-
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 79
TABLE 10. Geographic variation in 14 external and cranial measurements of Neotoma floridana
from Nebraska, Colorado, Kansas, Oklahoma, and Texas. See figure 8 for geographic areas
included within each coded locality.
Locality Males Females
Code N Mean + 2SE Range N Mean = 2SE Range
Total length
1 7 381.3 10.04 (361.0-398.0 ) 9 3144 9.88 (350.0-393.0 )
2. 9 379:6 11.04 (350.0-398.0 ) 8 365.8 9.40 (344,.0-382.0 )
3 OR oSpel: 10.25 (341.0-408.0 ) 19 376.4 6b (349.0-409.0 )
4 9 379.4 18.10 (345.0-434.0 ) IAS «63632 10.65 (340.0-402.0 )
5 Ie 386.0) 21-00 (376.0-397.0 ) 2 39720) 9 26:00 (384.0-410.0)
6 Dee oped 160 ( 342..0-370.0 ) 8 354.0 14.83 (329.0-395.0 )
T 14 3943 14.22 (349.0-450.0 ) ee oles 9.41 (340.0-397.0 )
8 15 380:0 11.99 (350.0-425.0 ) OD Sbrelt 10.87 (334.0-379.0)
9 20%) 359!5 Toth) (323.0-397.0 ) Mie S493 2205 (308.0-392.0 )
10 One O 11.29 (334.0-400.0 ) ey 352 9.82 (320.0-374.0 )
11 8 369.4 20.56 (328.0-420.0 ) 8 374.1 19.55 (322.0-340.0 )
119? 7 388.0 25.61 (317.0-414.0) 8 384.6 11.96 (356.0-412.0 )
13 4 407.0 18.20 (387.0-430.0 ) bre SOCOM 2ik3s (368.0-442.0 )
Length of tail vertebrae
1 7 159:7 1020 (138.0-176.0) 9 161.7 9.00 (136.0-180.0)
Seo 15500 S716 (13001670) 8 1572 481 (146.0-168.0)
3 12 1613 894 (120.0-178.0) 19 1585 4.06 (144.0-175.0)
eG Isai Got (130051740) 14) 1490) 55406 s6.0-1720)
Be) 1505" 29:00! (14510-1740) 2 1645 17.00 (156.0-173.0)
6 5 1486 6.65 (139.0-156.0) 8 1508 616 (142.0-169.0)
7 914 1629. 3:74 (153.0-175.0) 12) 1615 439)) (148.0-17000)
8 15 ~=160.7 6.79 (149.0-185.0 ) 9 154.4 6.07 (137.0-165.0 )
9 YAN) le3ayys: 5.39 (132.0-176.0 ) 16 = 150.3 5.02 (136.0-170.0 )
10 122 162.2 5.30 (143.0-172.0) 13 151.0 4.59 (138.0-163.0 )
lat: 9 WES 7/ 13.65 (130.0-195.0) 8 162.9 9.01 (138.0-174.0)
12 1 168.4 9.08 (147.0-181.0) 8 See, 6.48 (156.0-185.0 )
13 on LAO 21563 (159.0-195.0 ) 5 188.2 11.30 (175.0-207.0 )
Length of hind foot
8 39.8 0.60 (38.0-41.0) iE 39.1 0.51 (38.0-41.0)
10 41.8 1.26 (39.0-44.0 ) 8 39.5 0.65 (38.0-41.0)
) 19 39.8 0.77 (36.0-42.0 )
) 15 38.7 0.67 (36.0-40.0 )
) 2 42.0 0.00 ( 42.0-42.0)
) 10 36.8 1.36 (34.0-40.0 )
0) fat 39.3 0.90 ( 37.0-42.0)
14 39.5 1.75 (36.0-49.0 ) 10 37.5 1.31 (35.0-42.0
) 13 37.2 0.82 (35.0-40.0
) 13 38.2 1.14 (35.
) 8 38.5 1.65 (35.0-42.0
) (
) (
12 1 39.1 1.41 (37.0-42.0 11 39.3 1.01 36.0-42.0
13 4 38.8 1.50 (38.0-41.0 4 38.0 2.58 35.0-41.0
Length of ear
1 2 27.5 3.00 (26.0-29.0) 5 26.6 1.20 (25.0-28.0)
2 4 27.8 Ne7Al (26.0-30.0 ) 6 26.0 0.89 (25.0-28.0 )
3 6 28.8 1.89 (26.0-33.0) 9 28.7 1.05 (27.0-32.0 )
4 10 28.0 1.26 (25.0-31.0) 10 28.0 0.99 (25.0-30.0 )
5 3 26.3 2.40 (24.0-28.0) 2, 29.0 0.00 (29.0-29.0 )
6 6 26.7 1.33 (25.0-29.0) U 25.9 1.54 (23.0-28.0 )
ii Ili! 27.0 1.14 (25.0-30.0 ) 8 28.2 2.95 (25.0-38.0 )
8 11 Da 0.66 (26.0-30.0 ) 4 26.2 2.06 (24.0-29.0)
9 16 27.9 0.97 (25.0-32.0) 11 27.4 1.91 (25.0-36.0 )
10 10 27.2 1.07 (25.0-30.0 ) 1? 26.8 0.96 (25.0-29.0 )
11 8 28.5 1.00 (27.0-30.0 ) 5 27.0 3.03 (21.0-29.0 )
MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
TABLE 10.—Continued.
Locality Males Females
Code N Mean + 2SE Range N Mean + 2SE Range
12 3 lait 5.30 (25.0-33.0) 3 26.7 3.33 (25.0-30.0)
13 3 oe 2.91 (29.0-34.0) 3 30.3 2.91 (28.0-33.0)
Greatest length’ of skull
il 7 48.4 een (46.5-50.7 ) 11 48.8 0.44 (47.5-49.7 )
2 7 49.6 2.06 ( 46.0-53.8 ) 6 48.9 0.87 (47.5-50.6 )
3 12 Sle 0.81 (48.9-53.4 ) 18 49.7 0.72 (47.0-53.3 )
4 9 51.4 1.41 ( 48.4-55.2 ) 1k 49.7 0.74 (48.3-52.1)
5 3 Bes 2.66 (49.1-53.7) 2 52 1.20 (50.6-51.8)
6 5 50.1 1.58 (48.0-51.7) 10 48.6 0.94 (47.0-52.2)
i IN} 50.8 0.91 (47.4-53.5) 11 50.2 0.79 ( 48.6-52.1 )
8 15 50.5 Pats (47.1-54.0) 8 48.6 1.00 ( 46.8-50.7 )
9 16 50.2 0.82 (47.1-52.9) 14 48.2 0.84 (45.3-51.4)
10 13 50.2 0.69 (48.2-52.4) 13 48.3 1.01 (45.0-50.8 )
at 9 49.6 ers (44.4-53.0) 8 50.7 0.70 (49.5-51.9)
12 9 51.6 1.09 (49.8-54.0) 8 50.4 EOATE (47.9-53.2)
13 5 53.0 1.39 (50.7-54.5 ) 4 pA 1ST (51.0-54.1)
Condylobasilar length
1 7 47.4 Lees, (45.7-49.8 ) 11 47.4 0.55 (46.0-48.9 )
2; 9 48.6 1.71 (44.5-52.9 ) 1 47.6 0.77 (46.4-48.9 )
3 ils} 49.5 0.89 (47.3-52.3 ) 14 47.8 0.73 (45.2-50.9 )
4 9 50.6 1.47 (47.6-54.3) 12 48.6 0.81 (47.4-51.6)
5 3 49.3 3.27 (47.7-52.6) 2 50.1 1.20 (49.5-50.7)
6 5 49.3 1.61 (47.1-51.1) 10 47.2 0.99 (45.6-51.2)
a 15 49.5 0.99 (46.1-52.2) 11 49.0 0.93 (47.3-51.7)
8 16 49.2 1.15 (45.2-53.2 ) 8 47.2 0.93 (44.9-48.8 )
9 19 48.8 0.81 (45.5-52.4) 13 46.9 0.87 (50.0-54.0)
10 13 48.9 0.74 (47.1-51.0) 11 46.7 1.26 (42.9-49.3 )
ll 10 48.0 1.50 (43.2-50.9) 8 49.0 0.72 (47.6-50.5 )
12 9 50.1 1.29 (48.1-52.4) 10 48.4 1.04 (46.3-51.2)
13 5 50.6 1.63 (47.4-52.0) 5 49.4 1.98 (46.4-52.6)
Zy gomatic breadth
il of 25.9 0.61 (24.8-27.1) 1131 26.1 0.27 (25.4-26.6)
2 8 26.9 0.72 (25.4-28.6) Ml 26.4 0.49 (25.2-27.0)
3 12 27.4 2.14 (26.2-28.3 ) 15 26.8 0.44 (25.1-28.0)
4 10 27.8 1.02 (25.5-29.9 ) 12 27.1 0.67 (25.9-29.6 )
5 2 27.4 2.00 ( 26.4-28.4 ) 2 27.4 0.70 (27.1-27.8)
6 6 27.0 1.03 (25.7-28.9 ) 10 26.5 0.51 (25.6-28.3 )
a 13 27.9 0.53 (25.9-29.2 ) 12 27e3 0.49 (26:2-29.1 )
8 16 26.9 0.68 (24.4-29.0) 6 26.6 0.91 (25.4-28.1)
9 18 26.9 0.51 (24.4-28.9) 15 26.1 0.58 (24.0-27.9)
10 3 Dil 0.55 (25.2-28.5) 14 26.1 0.51 (23.3-27.1)
ll 9 Dial: 1.20 ( 22.8-29.3) 8 27.6 0.54 (26.1-28.3)
12 8 27.0 0.86 (25.5-28.7 ) 10 26.9 0.63 (25.5-29.2 )
13 4 PATE 0.80 ( 26.6-28.5 ) 5 26.8 LS (25.5-28.4)
Least interorbital constriction
1 9 6.9 1.70 (6.6-7.4 ) 11 6.6 0.15 (6.3-7.0)
2: 10 6.9 0.24 (6.4-7.7) 8 6.6 0.17 (6.2-6.9 )
3 14 7.0 0.15 (6.4-7.5) 19 6.8 0.16 (6.1-7.5)
4 14 6.7 0.18 (6.4-7.0) 13 6.6 0.13 (6.2-6.9 )
5 3 6.8 0.07 (6.8-6.9 ) 2 6.6 0.10 (6.5-6.6)
6 6 6.6 0.16 (6.4-7.0 ) 11 6.5 0.15 (6.2-6.9 )
of 16 6.7 0.22 (6.0-7.8 ) 12 6.6 0.21 (6.1-7.2)
8 18 6.8 0.18 (6.2-7.6 ) 10 6.7 0.24 (6.1-7.2)
9 22, 6.7 0.14 (5.8-7.2 ) 17 6.5 0.15 (6.1-7.3)
10 15 6.9 0.16 (6.5-7.5 ) 13 6.6 0.14 (6.2-7.2 )
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA
TABLE 10.—Continued.
Locality Males Females
Code N Mean + 2SE Range N Mean =+ 2SE Range
11 10 6.7 0.26 (6. 0-7 2) 9 6.9 0.16 (6.5-7.2')
12 9 6.8 0.23 ie 9-7.5) ial 7.0 0.24 (6.4-7.7)
13 5 7.0 0.19 (6.8-7.3 ) i 6.9 0.24 (6.7-7.3)
Breadth at mastoids
1 8 19.0 0.51 (18.0-20.4 ) 11 19.0 0.27 (18.2-19.6)
2 8 19.2 0.83 (17.4-20.7 ) 7 18.9 0.37 (18.1-19.3)
3 13 19.7 0.30 (18.7-20.5 ) 15 19.2 0.30 (18.1-20.2 )
4 11 20.3 0.63 (18.5-22.4) 14 19.7 0.34 (18.7-21.0)
5 2 19.8 0.70 (19.5-20.2 ) 2 2.0.0 0.50 (19.7-20.2 )
6 5 19.5 0.76 (18.5-20.6 ) 11 19.0 0.44 (17.8-20.1 )
fl 15 20.0 0.55 (16.9-21.0) 12, 19.4 0.42 (18.2-20.4 )
8 18 19.6 0.31 (18.2-20.7 ) 8 19.2 0.41 (18.5-20.2 )
9 18 19.3 0.22 (18.7-20.2 ) 14 18.8 0.39 (16.5-19.6)
10 15 19.8 0.31 (19.0-20.9 ) 13 19.0 0.28 (18.1-19.6)
iil 8 19.6 0.72 (17.4-20.6 ) 8 19.8 0.18 (19.4-20.1 )
12 8 20.0 0.49 (19.0-21.0) 10 19.8 0.51 (18.8-21.6)
13 5 20.5 0.68 (19.5-21.6) 5 19.4 0.55 (18.5-20.0 )
Length of rostrum
1 8 18.9 0.43 (17.8-19.6) iL 18.8 0.32 (17.5-19.4)
2 8 19.5 0.91 (18.0-21.9 ) 8 18.9 0.65 (17.3-20.0)
3 14 19.9 0.41 (18.7-21.2) 19 19.3 0.39 (Give8-21)
4 12 20.3 0.69 (17.9-22.9) 14 19.4 0.28 (18.7-20.5)
5 3 20.1 1.10 (le) pee leil)) 9} 20.6 0.30 (20.4-20.7 )
6 6 19.2 0.99 (17.7-20.5) 10 18.8 0.40 (18.1-20.0)
ih 16 19.8 0.46 (18.1-21.5) 11 19.5 0.39 (18.6-20.6 )
8 17 20.0 0.49 (18.4-21.6) 9 19.1 0.51 (18.2-20.4)
9 19 19.6 0.42 (18.2-21.1) 7 18.7 0.35 (17.3-19.9)
10 15 19.5 0.36 (18.2-20.4 ) 13 18.6 0.50 (16.4-19.5)
11 9 19.3 0.81 (17.0-21.0) fe) 19.9 0.43 (19.0-20.6 )
12 fe) 20.3 0.58 (19.1-21.7) 8 19.7 0.50 (18.9-20.7 )
13 5 ED 0.61 (20.1-21.9) 4 20.4 0.34 (19.9-20.7 )
Breadth of rostrum
1 9 7.9 0.17 (7.5-8.2 ) 18 7.9 0.13 (7.5-8.2)
2 9 8.2 0.58 (6.1-9.0) 8 8.1 0.16 (7.7-8.4)
3 15 8.7 0.15 (8.3-9.2 ) 17 8.4 0.18 (7.9-9.4)
4 12 8.5 0.36 (7.6-9.3 ) 15 8.5 0.14 (7.9-9.0)
5 3 8.3 0.35 (8.0-8.6 ) 2} 8.5 0.00 (8.5-8.5)
6 6 8.1 0.36 C6=87)) 10 8.0 0.15 (7.7-8.3 )
7 15 8.4 0.22 (7.5-9.1) 11 8.2 0.14 (7.8-8.5)
8 18 8.2 0.21 (7.6-9.0) 10 8.0 0.20 (7.5-8.5)
9 22, 8.0 0.15 (TA-8.7 ) ef 7.8 0.14 (7.3-8.2)
10 15 7.9 0.17 (7.3-8.5) 13 7.8 0.17 (7.4-8.3)
11 10 8.0 0.24 (7.1-8.4) 9 8.2 0.21 (EES)
12 8 8.2 0.31 (7.5-8.7) 10 8.4 0.33 (E5292)
13 5 8.2 0.34 (7.8-8.6 ) 5 8.3 0.27 (7.9-8.7)
Length of maxillary toothrow
1 9 9.5 0.20 (9.2-10.0) 11 9.4 0.17 (8.8-9.9)
2 10 9.3 0.23 (8.9-10.0) 8 9.4 0.38 (8.9-10.5)
3 15 9.9 0.18 (9.4-10.4) 19 9.7 0.12 (9.2-10.0)
4 12 9.6 0.19 (9.1-10.0) 15 9.7 0.16 (9.1-10.3)
5 3 9.6 0.64 (9.0-10.0) 2 9.8 0.40 (9.6-10.0)
6 6 9.7 0.28 (9.3-10.0) 11 9.3 0.21 (8.8-9.9 )
i 16 9.5 0.18 (9.0-10.2 ) 12, 9.4 0.23 (8.7-10.1)
8 19 9.6 0.15 (8.7-10.2 ) 10 9.4 0.26 (8.9-10.1)
9 22 9.3 0.15 (8.8-9.9 ) 17 9.2 0.14 (8.7-9.6 )
81
82 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
TABLE 10.—Concluded.
Locality Males Females
Code N Mean 2SE Range N Mean =+ 2SE Range
10 15 9.2 0.20 (8.5-9.8 ) 14 9.4 0.14 (9.0-9.9 )
11 8 9.4 0.26 (8.8-9.9 ) 9 9.4 0.24 (8.9-10.0)
1 9 9.0 0.28 (8.3-9.4) 11 9.1 0.22 (8.4-9.7 )
13 5 9.6 0.19 (9.4-9.9) 5 9.4 0.43 (8.8-9.9)
Length of palatal bridge
1 9 8.7 0.33 (8.2-9.6) 11 8.7 0.34 (7.3-9.2 )
2 9 8.5 0.30 (7.6-9.0) 8 8.1 0.28 (7.5-8.7)
3 15 8.8 0.23 (7.9-9.6) 19 8.4 0.15 (7.8-9.0)
4 12 8.9 0.37 (7.9-9.8 ) 15 8.6 0.24 (8.0-9.4)
5 3 8.7 0.74 (8.2-9.4) 2, 8.8 0.40 (8.6-9.0)
6 6 8.5 0.35 (7.9-9.0) 11 8.4 0.27 (7.6-9.0)
a 16 8.8 0.20 (8.1-9.6) 12 8.7 0.16 (8.3-9.3 )
8 18 8.6 0.32 (7.2-9.6) 10 8.3 0.18 (7.8-8.7)
9 22, 8.5 0.23 (7.6-9.7 ) 16 8.2 0.21 (7.5-9.0)
10 15 8.3 0.12 (7.9-8.8 ) 14 8.5 0.21 (7.6-9.0)
il 10 8.7 0.39 (7.8-9.5) 9 8.7 0.32 (8.1-9.5)
12 9 8.5 0.36 (7.7-9.4) 10 8.4 0.45 (7.3-9.8 )
lig 5 8.7 0.15 (8.6-9.0 ) 5 8.7 0.61 (7.9-9.7)
Length of nasals
i 8 18.7 0.43 (17.6-19.4) 11 18.7 0.33 (18.0-20.2 )
2, 8 19.3 0.89 (17.7-20.9) 8 19.0 0.48 (18.0-20.3 )
3 14 19.5 0.45 (18.3-20.9 19 19.0 0.37 (17.6-20.3)
4 12 20.3 0.71 (18.5-23.3 14 19.4 0.34 (18.5-20.4 )
5 3 20.5 ESS (19.3-21.6 2 20.6 0.50 (20.3-20.8 )
6 6 19.4 0.70 (18.5-20.7 9 18.7 0.40 (17.8-19.5)
U 15 19.9 0.42 (18.0-21.6 11 19.5 0.47 (18.6-21.3)
8 17) 20.0 0.51 (17.7-21.5 9 19.3 0.41 (18.3-20.5 )
9 19 19.8 0.49 (17.8-21.6 es 18.7 0.42 (16.7-20.2 )
10 15 19.7 0.47 (18.2-20.9 14 18.8 0.55 (16.5-19.8)
11 9 19.4 0.99 (17.3-21.9 9 20.1 0.49 (18.9-21.1)
12 9 20.5 0.68 (19.2-22.1 8 19.9 0.47 (18.8-20.7 )
13 5 Daler 0.94 (20.4-23.3 4 PAI 0.73 (20.2-22.0)
lated factors contribute to within-group
variation. Thus, trends in external char-
acters are not shown graphically, al-
though some of the observed trends were
not evinced by studies of cranial di-
mensions.
Standard statistics and geographic
variation in greatest length of skull are
illustrated as a graphic example of vari-
ation in a longitudinal cranial measure-
ment (Fig. 15, males; Fig. 16, females).
Results of SS-STP tests for this measure-
ment for both sexes are shown in table
11. Table 12 illustrates observed results
of samples of floridana and micropus
tested together. Also included are com-
parisons of subset relationships involving
additional variance between groups, and
results of SS-STP testing for greatest
length of skull for both species treated
simultaneously.
Comparisons of males show that spec-
imens from locality 11 are the smallest
end of a gradual north to south cline in
greatest length of skull. Females from
locality 11 are noticeably larger than
those from localities immediately to the
north and more nearly equivalent in size
to samples 12 and 13 from farther south
and east in Texas. Otherwise, males and
females are more or less similar with ex-
pected minor shifts in sequence of means.
Condylobasilar length was expected
to differ little from greatest length of
skull because both are measurements of
the long axis of the skull. However, a
remarkable amount of shifting in se-
quence of means is evident between the
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 83
TABLE 11. Results of SS-STP tests comparing means of greatest length of skull for males and
females separately from 13 localities of Neotoma floridana and 14 localities for N. micropus.
See figure 8 for geographic areas included within each coded locality.
|
| Males Females
| Maximal Maximal
| Locality non-significant Locality non-significant
code Mean subsets code Mean subsets
Neotoma floridana
13 53.0 I 13 52.3 I
12 51.6 erat 5 lee, ae)
4 51.4 Tee 11 50.7 | i |
5 Dies Jia 1 50.4 J foveas) (gE
3 piel eel ra 50.2 1G) Be Cas
ri 50.8 | Gare 4 49.7 Ganley cic} See
8 50.5 Tipe 3 49.7 lige ee eo Ee
9 50.2 eal 2, 48.9 |e Si I ee
10 50.2 1a | il 48.8 Ie oN Tey
6 50.1 ge 8 48.6 |e) Bae (iL
2 49.6 a 6 48.6 ) ieee) Ce
11 49.6 iran 10 48.3 el
il 48.4 I ) 48.2 I
Neotoma micropus
Li 51.0 I D 49.7 If
H 50.6 ees | © 48.8 | oe |
D 50.5 |G 6 | B 48.8 or
C 49.7 1d Wiles Cale | it 48.6 | gga hoes
G 49.6 | gel Game (uses) igh i | I 48.5 | ued Bnd |
A 49.4 To gk Serie G 48.3 | Fi ge i
B 49.2 1 ee nal ge aa F 47.7 a te “se er
K 48.7 1 ed A Dae | H 47.6 Ei Ts Sit
I 48.3 [foe 2 a | K AT.1 1 AGI a aa
F 48.1 ort ht M 46.7 1 a (Pf
ij 47.9 | Ee) be i Le A 46.5 Lr
N 46.8 ler J 46.2 Li
P 46.6 It P 45.8 I
M 46.6 I N 45.7 I
itwo characters. Also, no significant dif-
ferences were detected in group-means
of males for condylobasilar length.
No significant differences exist among
group-means for zygomatic breadth of
males. Although specimens of rubida
(13) are larger, on the average, than in-
dividuals from more northerly samples
of the species in the measurements of
longitudinal axis of the skull, they are
narrower in zygomatic breadth than
males from localities 7 and 4 (Fig. 17).
However, the differences are not sig-
nificant. Highly significant (P< 0.01)
differences were detected in zygomatic
breadth of females (Fig. 18).
Least interorbital constriction is one
of the least variable measurements con-
sidered for N. floridana. Group-means
are not significantly different for males,
and sequence of means for this character
(Fig. 19, males; Fig. 20, females) does
not follow that seen in other measure-
ments for either sex. The pattern of
geographic variation in mastoidal
breadth closely approximates that seen
for zygomatic breadth.
Woodrats from localities 3, 4, and 5
(the two samples of campestris from
northwestern Kansas and the sample of
attwateri from adjacent north-central
Kansas) are generally larger in breadth
of rostrum than are woodrats from south-
em Texas (12 and 13). In measure-
ments of length, specimens from locality
13 are consistently larger than specimens
from northern Kansas. It is visually per-
ceptible that the skulls of specimens of
84 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
campestris tend to be broader, more
heavily structured and robust than those
of rubida. To a lesser extent the same
differences prevail between campestris
and attwateri with the exception of spec-
imens from locality 5. The latter are like
other samples of attwateri in color, but in
several aspects of overall size and general
shape of the skull, they more closely re-
semble campestris.
Patterns of variation for alveolar
length of the maxillary toothrow are
similar to those of rostral breadth, but
unique in certain aspects. Notably, spec-
imens from locality 12 are smallest both
for males and females, whereas those
from localities 1 (baileyi) and 6 (north-
eastern Kansas), which are among the
smallest in most dimensions, are rela-
tively much larger. Results of computa-
tions for this measurement also are some-
what unique in that more total variation
exists between means of males than be-
tween those of females.
Of the dimensions analyzed, palatal
bridge length demonstrates the least
amount of geographic variation. Group-
means are not significantly different for
males and are significant only at the
0.05 level for females. Coefficients of
variation for measurements of this char-
acter are noticeably larger than for other
cranial dimensions. The reduction in
significant geographic variation in length
of palatal bridge may be a result of high
within-group variation.
Geographic variation in nasal length
exceeds that for other cranial dimen-
sions. Geographic trends for this de-
mension are similar to those for length
of rostrum. These two measurements in-
clude the same region of the skull, but
TABLE 12. Results of SS-STP tests comparing means of greatest length of skull for males and
females treated separately and localities of Neotoma floridana and N. micropus tested simul-
taneously. See figure 8 for geographic areas included within each coded locality.
Males
Maximal
non-significant
subsets
Locality
code Mean
13 53.0
12 51.6
51.4
51.3
51.1
51.0
50.8
50.6
50.5
50.5
50.2
50.2
50.1
49.7
49.6
49.6
49.6
49.4
49.2
48.7
48.4
48.3
48.1
47.9
46.8
46.6
46.6
OGMarwourw
—
QDADMSOCH
=
OO
me
en Al cee cen OL eon fl ce Bl cern ce ee ee ee ee ee
en fl seen fll cen OL een ce ee es ce Oe en ee ee ee
ee OO
Ln A ee cn Oe Oc ce cee ce eB ee en oe
=
eo Ae 5 ee oo ae We)
ee OO
Ln ll een eee I ces fl oe BE en ce en ce en cee ee Bl |
re
—
Females
Maximal
non-significant
subsets
Locality
code Mean
13 52.3
5 51.2
a 50.7
50.4
50.2
49.7
49.7
49.7
48.9
48.8
48.8
48.8
48.6
48.6
48.6
48.5
48.3
48.3
48.2
47.7
47.6
47.1
46.7
46.5
46.2
45.8
45.7
ZrmourZSartnoSoQnoaltortwOnwJarab
Le A cee Hl seen Nl eee Hl eee en een eee ae ae Hl ee ee |
me OS
OO
me
OO
Ln A ee A eee ec FN ee ee en cen BO en Od ce Bd ee en |
OR
me OO OR
ee
|e A cee cn ces ce Be Oe ce ce ce Bl |
Le ee ee Oe Oe ee |
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 85
differ in that rostral length is in part
dependent on shape of the anterior end
of the zygomatic arch.
When all measurements are con-
sidered, there is general agreement be-
tween the patterns of variation as indi-
cated by separate analyses of males and
females except for specimens from lo-
cality 11 (northern Texas). Males from
that locality are smaller (as determined
by rank-order scoring of means for the
14 characters) than samples of males
from all localities except northeastern
Oklahoma (9). Rank-order scores of
males from localities 9, 11, 6, and 1 were
so close as to be indistinguishable by
this method of analysis. In comparisons
of females, however, specimens from lo-
cality 11 were surpassed in total size only
by those from samples 5 and 13.
When the rank-order scores for males
and females are summed, a general trend
of geographic variation for floridana in
the Central Great Plains can be seen.
Neotoma floridana rubida is slightly
larger than any of the samples of attwa-
teri or campestris, and appreciably larger
than baileyi. Specimens of campestris
from localities in Kansas are larger than
those from Colorado and larger than
specimens of attwateri from all except
adjacent localities in north-central Kan-
sas. Within the subspecies attwateri,
there is appreciable variation in size, but
this variation does not follow expected
trends. Specimens from north-central
Kansas (5) are largest, followed in se-
quence by those from southern Texas
(12), southeastern Kansas (7), and west-
ern Oklahoma (8). Specimens from east-
ern Oklahoma (9 and 10) and northeast-
ern Kansas (6) are the smallest examples
of the subspecies. Neotoma floridana
baileyi is slightly larger than the smaller
representatives of attwateri, but smaller
than the larger representatives of that
subspecies. The only contiguous locali-
ties from which samples of specimens
frequently are significantly different in
size are those in north-central Kansas
(5) and northeastern Kansas (6). How-
ever, on the basis of color, specimens
from these localities are similar and indi-
viduals in both samples are significantly
darker than specimens of campestris.
Neotoma micropus and N. angusti-
palata—In univariate analysis of geo-
graphic variation in Neotoma micropus
and N. angustipalata, specimens from lo-
calities O (White Sands National Monu-
ment, New Mexico) and Q (Rio Verde,
San Luis Potosi) were not included in
UNIVAR computations because only
single specimens were available. Sample
R (N. angustipalata) was not included
because only one adult specimen of each
sex was available at the time UNIVAR
analyses were conducted. Subsequently,
two additional adult females were exam-
ined and included with calculations of
standard statistics shown in table 13.
Sample E (N. m. canescens from New
Mexico ) also was omitted from UNIVAR
analyses because New Mexico was not
included in the study area at the time
computations were conducted. Standard
statistics of this sample are shown in
table 13. In all four instances, sequence
of means were considered for rank-order
analysis of trends in size variation, but
significance levels are not known for
these four samples.
Considering the remaining 14 sam-
ples of N. micropus, differences in group-
means of total length are not significant
for males, but they are significant (P<
0.05) for females. Specimens from lo-
calities N and P (coastal Tamaulipas)
are relatively large in this character,
whereas those from adjacent Coahuila
and Nuevo Leon are small. Specimens
of both sexes from localities P and N
(N. m. micropus) have the longest tails
of any samples of the species. This is in
marked disagreement with trends in cra-
nial measurements, wherein specimens of
N. m. micropus are among the smallest.
Furthermore, they exhibit a marked ten-
dency toward being unicolored, espe-
cially in southern parts of Tamaulipas.
Although somewhat variable and less
reliable than cranial measurements, ex-
ternal dimensions demonstrate certain
overall trends. The two samples com-
86 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
_
o0o”MWO WON AO WH & WwW DN
Localities
zx onmooo p
ir Om Om aa see) ao
42:5 43:5 44°55 45:5 46:5 «47:5 48.5 949'5 50:5 51/5° 52°55 953°5)54'5)) (5535
mm
Fic. 15. Dice-grams illustrating geographic variation in greatest length of skull of male Neotoma
angustipalata, N. floridana, and N. micropus. The upper point of the triangle is the arithmetic
mean; the darkened bar is plus and minus two standard errors of the mean; the open bar is plus
and minus one standard deviation of the mean, and the horizontal or vertical lines indicate the
range. See figure 8 for geographic areas included within the coded localities indicated on the ordinate.
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 87
Localities
zon i moo0onw »,p 0 ON OO WN RB W bw =
> VZz Ss rFexKe
| 43.0 440 450 460 470 48.0 49.0 50.0 510 52.0 53.0 54.0
mm
Fic. 16. Dice-grams illustrating geographic variation in greatest length of skull of female Neo-
toma angustipalata, N. floridana, and N. micropus. See figure 15 for explanation of symbols and
figure 8 for geographic areas included within the coded localities indicated on the ordinate.
88 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
oO ON Ou fF WD =
Localities
zo Tem oC 1 =
7 oO vo 2 2 =x ol
230 23:5 240 24/55 250 255: 26:0 26:5. 270: 275 28:0 28:5 2910 (2915
mm
Fic. 17. Dice-grams illustrating geographic variation in zygomatic breadth of male Neotoma
angustipalata, N. floridana, and N. micropus. See figure 15 for explanations of symbols and figure
8 for geographic areas included within the coded localities indicated on the ordinate.
Localities
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 89
Oo WO NOW fF W PD =
23:0) 23:5) 24:05) °24:5, 25.0, (25:55 «26:0 26:5 «270 27:5. 28:0 28:5 29:0 295
mm
Fic. 18. Dice-grams illustrating geographic variation in zygomatic breadth of female Neotoma
angustipalata, N. floridana, and N. micropus. See figure 15 for explanation of symbols and figure
8 for geographic areas included within the coded localities indicated on the ordinate.
90 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
Localities
=- ronrnmooiow ep 0 ©) <7 OF Ul wh)
ya OwveozezksrxK «=
5.5 5:7 59 6.1 6.3 6.5 6.7 69 TA 7.3 75 7.7 719
im m
Fic. 19. Dice-grams illustrating geographic variation in least interorbital constriction of male
Neotoma angustipalata, N. floridana, and N. micropus. See figure 15 for explanation of symbols and
figure 8 for geographic areas included within the coded localities indicated on the ordinate.
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 91
—
o OnN OD ON BW bw
Localities
2B) Dwi 5.9 6.1 6.3 6.5 6.7 6.9 71 3 1) tll
mm
Fic. 20. Dice-grams illustrating geographic variation in least interorbital constriction of female
Neotoma angustipalata, N. floridana, and N. micropus. See figure 15 for explanation of symbols and
figure 8 for geographic areas included within the coded localities indicated on the ordinate.
92 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
posed of largest individuals (exclusive of
the tail) tend to be L and D. Locality L
is composed of specimens from along the
Gulf Coast of Texas and D represents
specimens from south-central Kansas.
Specimens from localities N and P (N.
m. micropus) have noticeably longer tails
than even the samples of N. m. canescens
characterized by large size. Specimens
from southwestern Texas, in the general
region of the Big Bend area (J), appear
smallest in external characters.
Geographic variation in greatest
length of skull is shown graphically for
Neotoma micropus in figures 15 (males)
and 16 (females). Results of SS-STP
tests illustrating maximally connected
non-significant subsets for this dimension
are given in table 11 for tests conducted
only on the specimens of N. micropus
from grouped localities, and in table 12
for tests made when specimens from
grouped localities of N. floridana and N.
micropus were tested simultaneously.
Means of samples of the two species
overlap broadly, but samples shown to
be significantly different by the two
methods are generally the same.
The pattern of geographic variation
seen in this measurement is typical of
most cranial measurements. The sam-
ples of largest woodrats are from locali-
ties L (southern coastal Texas), C, D,
and G (south-central Kansas and ad-
jacent western Oklahoma inclusive of the
panhandle). The smallest are N. m. mi-
cropus (N and P) from Tamaulipas and
N. m. canescens from samples J (south-
west Texas) and M (Coahuila and
Nuevo Leon). Specimens from other lo-
calities tend to form gradual clines with
the large and small samples listed above.
The single exception is the marked
change in size between specimens from
coastal Texas (N. m. canescens, locality
L) and northern Tamaulipas (N. m.
micropus, locality N ).
Specimens of both sexes from locali-
ties in Colorado, Kansas, northern Texas,
and Oklahoma generally are larger in
condylobasilar length than those from
southern localities, including sample I
(northeastern part of the range in Texas
just south of the Red River). The only_
breaks in this trend result from the large
size of specimens from the Gulf Coast
of Texas and the relatively small size of
females (A) from Colorado. Geographic
trends in zygomatic breadth are shown
in figures 17 (males) and 18 (females). |
Except the females from Colorado (A)
appear larger and more nearly the size
of females from other northern localities,
these are comparable to those discussed
for condylobasilar length.
Trends in geographic variation of the
least interorbital constriction are shown
in figures 19 (males) and 20 (females).
This dimension differs from other cranial
characters of micropus in three respects.
First, variation in group-means is not sig-
nificant for females. Second, means of
both sexes from locality L are relatively
low, placing this population more nearly
with others in the southern part of the
distribution rather than with the larger
northern populations. Thirdly, specimens
from locality H, which generally are in-
termediate in size (especially females),
have the broadest average interorbital
constriction. Interorbital constriction is
consistently broader in floridana than
micropus, and the possibility exists that
the wide constriction in specimens of
micropus from these localities has_re-
sulted from introgression of floridana
genes.
The pattern of variation for breadth
at the mastoids is typical of most cranial
measurements save for the unusually
large size of specimens from localities A
and B. Analysis of rostral length, espe-
cially for males, exemplifies the north to
south and east to west clines in diminish-
ing size. The pattern of geographic vari-
ation in rostral breadth deviates from
this general trend of variation in the
large size of males from locality J (south-
western Texas). In other characters,
woodrats from locality J tend to be more
like the smaller woodrats from western
and southern parts of the range of the
species.
Variation in alveolar length of maxil-
WOODRATS (GENUS NEOTOMA)
IN CENTRAL NORTH AMERICA
TABLE 13. Geographic variation in 14 external and cranial measurements of Neotoma
micropus and N. angustipalata. See figure 8 for geographic areas included within each coded
locality.
Locality Males Females
Code N Mean =+ 2SE Range N Mean + 2SE Range
Locality
A OeoGOses 1073) = ((S53.0-571.0) 10 348.5 12.74 (318.0-372.0)
B 8 364.4 17.76 (340.0-410.0 ) 13) Gores 8.08 (323.0-381.0 )
C lowe Soul Wills} (334.0-411.0) 18 354.8 8.62 (310.0-382.0 )
D 8 3/48 12.45 (351.0-404.0 ) 14 362.3 10.52 (337.0-398.0 )
E 3} SPAILD) 16.04 (305.0-330.0 ) 5 329.0 18.25 (310.0-354.0 )
F 7 362.7 10.58 (340.0-380.0) 8 358.5—) 1246" ((33310-378.0)
G A363.) 8.89 (355.0-376.0) 10 35a9 8.21 (328.0-373.0)
H by Ba 12.42 (348.0-385.0 ) io SANE 11.14 (311.0-355.0)
I Jae 3584 1021 (317.0-398.0) 30 345.3 9.32 (303.0-400.0)
J 4 358.2 10.72 (350.0-374.0) 8 330.1 12:16 ~ (81010-352.0)
kK 7 350.3 23.44 (302.0-380.0) 7 9351.3 22.63 (304.0-390.0)
L Cee ono ON) 22572) (348.0-422.0 ) 8 365.9 18.16 (319.0-388.0 )
M 12 345.4 1G) Be? (302.0-368.0 ) 12 339) 9.40 (313.0-366.0 )
N 9 370.3 9.78 (349.0-390.0 ) 2 9361.5 23:00 (350.0-373.0 )
0 i 3ls:0 eae | =) 0 = :- ( 1)
2 3.) 364:3 2.40 (362. 0-366. 0) 4 3545 24.84 (333. 0377. 0)
Q ee Sok.0 ( z) 0 ae el 3)
R 1 402:0 ( _) 3° 3903 25:36 (365. 0-404. 0)
Length of tail vertebrae
A 3) deere 481 (135.0-143.0) 10 += 139.6 429 (130.0-150.0)
B Sml45.2 7.28 (131.0-160.0) ie | 14428 4.36 (130.0-157.0)
C 15 156.6 5.99 (135.0-175.0 ) 18 148.8 5.51 (130.0-165.0)
D 8 147.0 9.19 (120.0-164.0) 14 148.7 Delis (126.0-168.0)
E Sy Ber foley (120-134) 0) Hee 3or6 7.60 (126.0-144.0)
F 7 146.3 6.34 (133.0-156.0 ) 8 152.9 7.68 (138.0-170.0 )
G 4 149.0 3.74 (145.0-154.0) 10M 502 4.99 (136.0-162.0)
H lara 1OO7 iC 13610-16510) 7 149.6 5.40 (138.0-159.0)
I 22 146.0 4.98 (129.0-166.0) 30 §6144.8 5.39 (120.0-195.0)
Vf 4 148.5 8.19 (140.0-156.0) 8 137.4 10.65 (110.0-153.0)
K 7 149.7 10.62 (126.0-169.0) a 149.9 7.65 (133.0-161.0)
ify Ga 15633 9.53 (150.0-180.0) See 57-5 6.29 (147.0-173.0)
M 13 141.2 6.33 (113.0-154.0) 12 140.4 4.88 (121.0-153.0)
N 9 1649 7.00 (147.0-177.0) 2 1645 P5007 2 C1502172.0)
O i $120:0 Aes Bil 3) 0 ae eee Mega" feee )
iP, 3 169.7 4.06 ( 166.0-173. 0) AS NS Ovi ae w ( 155.0-193. 0)
Q ey A167.0 ( z=) 0 = ae (ae )
R 1 200.0 ( 7s) 3 1907 — TTS: * ( 179.0-198. 0)
Length of hind foot
A 6 38.0 ESIC (35.0-40.0) 10 37.3 1.08 (34.0-39.0)
B 9 38.7 1.76 (36.0-45.0) 13 38.5 0.89 (36.0-41.0)
C 16 39.5 1455 (35.0-43.0) ef 38.4 0.68 (36.0-41.0)
D 9 40.2 0.93 (38.0-42.0) 15 39.1 0.73 (37.0-41.0)
E 3 36.3 0.67 (36.0-37.0) 6) 36.6 1.85 (35.0-40.0 )
F 6 OieD 235 (33.0-41.0) 8 35.9 0.80 (34.0-37.0)
G 5 38.2 1233 (36.0-40.0 ) 9 38.2 1.14 (36.0-41.0 )
H i 36.6 WT (35.0-39.0) 8 37.0 1.20 (35.0-40.0 )
I PAL 3o1.3 1.54 (28.0-43.0) 31 36.7 0.79 (32.0-40.0)
i 4 36.0 0.82 (35.0-37.0 ) 8 34.6 25 (33.0-38.0 )
K 9 39.1 0.62 (38.0-40.0 ) a 36.6 2.64 (30.5-40.0 )
1 6 40.3 1.91 (37.0-43.0) 7 39.9 1.45 (37.0-43.0 )
M 13 Oiled. 1.49 (32.0-41.0) 1 37.9 0.87 (36.0-41.0)
N 10 30.0 1.00 (35.0-40.0 ) 3 Silke 3s (36.0-38.0 )
O 1 36.0 = (i) 0 ah ms (en A)
P 3 38.0 iets) (37.0-39.0 ) 4 36.5 1.29 (35.0-38.0 )
93
94
MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
TABLE 13.—Continued.
Locality Males Females
Code N Mean =+ 2SE Range N Mean + 2SE Range
Q 1 38.0 (ea rc 5§) 0 e a (oo SE a)
R 1 42.0 (ak a) 3 38.7 2.91 (36.0-41.0)
Length of ear
A 6 28.3 0.42 ( 28.0-29.0) 9 27.0 0.94 (25.0-29.0)
B 9 ipl 1.02 (25.0-29.0) 12 He les: 0.62 (25.0-29.0)
C 7 27.0 1.07 (25.0-29.0) 12 26.8 0.95 (25.0-30.0 )
D 6 28.2 0.61 ( 27.0-29.0) sa 28.1 igi (25.0-32.0)
E 3 26.3 1.76 (25.0-28.0) 5 28.4 1.85 ( 27.0-32.0)
F 4 25.2 Soli (20.0-28.0 ) 6 28.2 0.61 (27.0-29.0)
G 5 27.0 1.10 (25.0-28.0) 1 26.1 0.81 (25.0-28.0)
H 6 26.3 0.42 (26.0-27.0) 6 26n 0.99 (25.0-28.0)
I eT 25.9 eS (20.0-30.0 ) 24 25.9 0.79 ( 22.0-30.0)
Ij 4 26.2 3.40 ( 22.0-29.0) 8 26.1 1.33 (23.0-28.0)
K 6 28.8 2.39 (25.0-34.0) 2 23.5 7.00 (20.0-27.0)
Je 6 28.2 1.50 (25.0-30.0 ) 6 29.1 1.42 ( 27.0-32.0)
M 12 28.7 0.92 (26.0-31.0) 10 28.4 0.84 (26.0-30.0)
N 10 29.4 0.90 (27.0-32.0) 3 29.0 1S (28.0-30.0)
O 0 = a (Cae) 0 i ae (Cr Se
P 2 28.0 2.00 (27.0-29.0) 4 28.2 2:22 (25.0-30.0 )
Q 0 ae ( =) 0 = —_ ( sz.) Pass
R 1 36.0 ( )) 3 28.7 Ses: (27.0-32.0)
Greatest length of skull
A 6 49.4 leltzé (47.9-51.4) 9 46.5 1.20 ( 43.0-48.8 )
B 11 49.2 0.78 (47.6-51.6) 12 48.8 0.86 (46.1-51.3)
G 14 49.7 0.95 (46.4-52.9) 15 48.8 1.09 (44.2-51.8)
D 9 50.5 0.95 (48.8-53.4) its 49.7 0.56 (48.0-51.4)
E 3 46.6 0.53 (46.2-47.1) 4 47.0 233 (43.8-49.2 )
F 6 48.1 0.61 (47.0-49.0) 8 AT.7 0.81 ( 46.0-49.2 )
G 5 49.6 1.65 (47.6-52.1) 8 48.3 0.55 (47.1-49.0)
H u 50.6 1S (48.6-53.4) 8 47.6 1215 (45.2-50.5)
I 19 48.3 0.86 (43.8-51.1) 28 48.5 0.65 (45.3-51.5)
J 3 47.9 1.58 ( 46.3-48.8 ) 8 46.2 ila ye (44.0-48.8 )
K U 48.7 0.86 (47.5-50.5 ) 6 47.1 1.08 (45.9-49.5)
iL 6 51.0 1.50 (47.9-53.0) il 48.6 127 (45.9-50.8 )
M Le 46.6 0.92 (42.5-48.5 ) 11 46.7 1.07 (43.9-49.3 )
N 8 46.8 1.58 (43.9-50.0 ) 2 45.7 1.80 (44.8-46.6 )
O 1 44.9 me (Ca eee at) 0 a £3; (Se)
P 3 46.6 0.42 ( 46.2-46.9 ) 4 45.8 1.49 (43.9-47.1)
Q 1 44.9 a ( =) 0 ase cell (eae)
R 1 51.0 ( =) 2 49.8 0.10 (49.7-49.8 )
Condylobasilar length
A 6 48.8 0.95 (47.7-50.3 ) 9 45.1 1.38 (41.1-47.5)
B 1 48.2 0.75 (46.1-49.9 ) 13 47.0 0.68 (44.8-48.8 )
( 13 48.3 1.06 ( 44.6-50.9 ) 16 47.1 0.92 ( 42.8-50.0)
D 9 49.1 0.74 (47.2-51.3) 15 47.8 0.51 (45.7-49.2 )
E 3 44.8 1.05 ( 43.8-45.6 ) 5 45.1 1.60 ( 42.3-47.0)
F 7 46.9 0.77 (45.4-48.3 ) 8 46.1 0.66 (44.7-47.1)
G 5 AT.7 0.92 (46.6-49.2 ) 8 46.3 0.78 (45.0-47.8 )
H 8 48.4 0.76 ( 46.7-49.7 ) 8 45.9 1.08 (43.7-48.4)
I 22, 46.9 0.79 (42.6-49.6) 30 46.4 0.58 (43.7-49.9 )
J 3 46.5 1.14 (45.4-47.2) 8 44.7 1.36 (41.7-47.5)
K U 46.7 0.91 (45.0-48.8 ) 7 45.6 1.10 (43.8-48.1 )
L 6 49.4 1.48 (46.1-51.1) ¢ 46.8 1.21 (44.2-48.9)
M 11 44.7 0.93 (41.3-46.2 ) 11 44.5 0.84 (41.9-46.7 )
N 8 45.2 1.40 (42.7-48.5 ) 2 44,4 0.80 (44.0-44.8 )
O 1 43.9 (ere Soc) 0 (ger ates)
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA
TABLE 13.—Continued.
Locality
Code
P
Q
R
HOWOZS EAHA KH tesahoaePS
DOWOZZrPAKH TODA DOePS
rad halle ly |p )les| lea) te) (apy lool
—_
ot Ee o| &
bo
RSPR WrOWaIWwWwoawtdwoiuwir Dd
_— jd
bo
BPR WORE WRDOWRDWOUNWODF D
—
— He
—
Males Females
Mean + 2SE Range N Mean + 2SE Range
44.2 0.75 (43.6-44.9 ) 4 43.2 1.44 (41.7-44.5)
44.0 ae (ee ee) 0 al a3 (Cee) Te)
49.6 (Ape eee!) 2 47.4 0.30 (47.3-47.6)
Zygomatic breadth
Dial: 0.90 (25.4-28.5) 8 26.3 0.99 (23.8-28.2 )
26.5 0.55 (25.1-28.0) 13 26.7 0.70 (24.7-29.1 )
26.8 0.48 (25.5-28.8 ) yf 26.5 0.45 (24.9-28.4 )
Niles’ 0.45 (26.7-28.9 ) 15 26.8 0.44 (25.5-28.4)
25S 0.64 (24.7-25.8 ) 5 25.2 0.99 (247322 7/al)
26.5 0.39 (26.0-27.4) i 26.1 0.70 (24.6-27.6)
26.5 0.75 (Q5:5=2725)) 10 26.1 0.60 (2405-2772)
pl 0.67 (26.2-29.1 ) 8 25.8 0.51 (25.0-26.5 )
26.1 0.41 (235722704) 32 26.1 0.36 (23.0-28.1 )
25.3 0.20 (25.2-25.5) 8 25.1 0.40 (24.3-26.0)
25.8 0.81 (25.0-28.0 ) ih ess 0.58 (24.8-26.8 )
27.6 0.88 (25.9-28.9 ) il 25.8 0.80 (24.6-27.3)
24.8 0.50 (23:9-25;7 ) fat 24.6 0.39 (23.6-25.3 )
24.9 0.82 (23532264) 2; 24.9 1.00 (24.4-25.4)
25.4 Jus im on SANS 0 = = CP Ae Oe
25.0 giles (24.4-26.2 ) 4 24.0 0.38 (23.5-24.4)
235 (Gen =*) 0 = aie (amar SS)
25.8 ( =) 2 25.0 2.00 (24.0-26.0)
Least interorbital constriction
6.4 0.23 (6.1-6.9 ) 10 6.3 0.21 (5.8-6.8 )
6.2 0.16 (5.8-6.7 ) 14 6.3 0.16 (5.8-6.7)
6.4 0.13 (6.0-6.9 ) 18 6.3 0.15 G9=720))
6.4 0.12 (6.1-6.7 ) 16 6.4 0.14 (5.9-7.0)
6.0 0.13 (5.9-6.1 ) 5 6.2 0.32 (5.9-6.8 )
6.2 0.12 (6.0-6.4 ) 8 6.3 0.23 (5.8-6.7)
6.4 0.41 (5.9-6.9 ) 10 6.4 0.21 (5.8-6.9)
6.6 0.33 (6.1-7.7) 8 6.4 0.24 (5.9-6.9 )
6.4 0.14 (WEA) 33 6.3 0.15 (5: 5-162)
6.3 0.07 (6.3-6.4 ) 8 5.9 0.18 (5.7-6.3)
6.1 0.19 (5.7-6.6 ) 7 6.1 0.16 (5.9-6.5)
6.2 0.21 (5.8-6.5) a 6.1 0.24 @557-6!5))
6.2 0.18 (5.8-7.0) 12 6.2 0.13 (5.9-6.8 )
6.1 0.18 (55-615) 3 6.0 0.31 (5.7-6.2;)
6.0 a (Gy Sea ) 0 =a my 0. (ee
6.0 0.29 (5.8-6.3) 4 6.3 0.36 (6.0-6.8 )
5.6 (aia ) 0 “uae 25 nee (meres
Dall (a ) 2 6.0 0.30 (5.8-6.1)
Breadth at mastoids
19.9 0.57 (18.9-20.9) 8 18.9 0.50 (18.0-19.9 )
19.1 0.40 (18.0-20.1 ) ill 19.3 0.35 (18.3-20.3 )
19.5 0.38 (18.1-20.8 ) 16 18.9 0.27 (17.9-19.8 )
19.6 0.25 (19.1-20.1 ) 14 19.0 0.23 (18.2-19.5)
18.4 0.76 (17.7-19.0) 5 18.3 0.53 (17.5-19.0)
18.9 0.59 (17.6-20.0 ) 8 18.8 0.29 (18.2-19.3)
19.2 0.49 (18.7-20.1 ) 8 18.9 0.42 (17-7196)
19.6 0.23 (19.0-20.0) 0 19.0 0.58 (18.2-20.1 )
18.9 0.26 (18.0-20.0 ) 25 19.0 0.27 (76-2057)
18.8 0.46 (18.2-19.3) 8 18.5 0.32 (17.8-19.2 )
19.0 0.40 (18.5-20.1 ) 7 18.8 0.38 (18.0-19.7 )
19.7 0.42 (18.9-20.5 ) 8 19.4 0.50 (18.4-20.6)
19.0 0.47 (17.5-19.9) 10 18.6 0.23 (17.8-19.1)
18.8 0.71 (17.5-20.4 ) 2, Ie 0.20 (17.6-17.8 )
95
96
MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
TABLE 13.—Continued.
Locality Males Females
Code N Mean = 2SE Range N Mean + 2SE Range
O 1 18.1 gay (Cera, pars) 0 an te: (gee es
[es 3 18.3 0.44 (18.0-18.7 ) 4 18.2 0.48 (17.6-18.6)
Q 1 18.0 = ¢ me) 0 ae me ( =e
R 1 19.5 cs ( = ) 2 18.9 0.20 (18.8-19.0)
Length of rostrum
A 6 19.5 0.69 (18.5-20.7 ) 9 i eferh 0.63 (18.8-19.0)
B 11 19.2 0.40 (18.2-20.2 ) Ss 18.8 0.44 (AITETEZ.0 23)
C 15 19.5 0.37 (17.8-20.7 ) 17 18.9 0.36 (17.2-20:1)
D 9 19.9 0.67 (18.6-21.6) 16 19.9 0.34 (18.6-20.8 )
E 3 17.9 0.77 (17.5-18.7) 4 18.2 tals (16.7-18.6)
F ra 18.7 0.20 (18.5-19.2) 8 18.5 0.35 (17.7-19.2)
G 5 19.0 0.59 (18.2-20.0 ) 10 18.8 0.47 (17.6-20.1 )
H a 19.8 0.49 (18.7-20.7 ) 8 18.6 0.52 (17.6-19.7)
I 21 18.9 0.41 (16.6-20.2 ) 30 18.8 0.31 (@iE3=20570)
J 4 18.5 0.89 (17.2-19.2) 8 Let fart 0.69 (16.6-19.4)
K 9 18.9 0.46 (17.9-20.0) fl 18.2 0.51 (17.0-19.2)
IL. 6 19.8 0.94 (17.7-20.9 ) 8 18.6 0.74 (17.0-20.5 )
M 13 WPT 0.47 (15.7-18.6 ) 12, io 0.56 (16.0-18.9
N ll 16 0.63 (16.0-19.7 ) 3 2 0.98 (16.2-17.8)
O i 17.4 as (eed =m) 0 = ae (aes EES)
iP 3 17.4 0.47 (17.0-17.8) 4 17.6 0.91 (16.4-18.5)
Q 1 yea (i SEES 3) 0 a pa (iz. © me
R 1 20.7 ( =) 3 19.1 0.50 (18.8-19.6)
Breadth of rostrum
A 6 8.6 0.47 (8.1-9.3) 9 7.9 0.30 (7.0-8.5)
B 11 8.3 0.26 (7.5-9.2 ) 14 8.2 0.23 (7.2-8.9)
¢ 16 8.4 0.16 (7.8-9.0) 18 8.3 0.18 (7.7-9.3)
D 9 8.5 0.23 (8.1-9.1) 16 8.3 0.17 (7.7-9.1)
E 3) 7.9 0.12 (7.8-8.0) 5 8.1 0.36 (8.2-8.4)
F 7 8.2 0.18 (7.8-8.5) 8 7.9 0.11 (7.7-8.2)
G 5 8.3 0.20 (8.0-8.6) 10 8.1 0.23 (7.6-8.6)
H 8 8.2 0.23 (7.7-8.7) 8 7.9 0.24 (7.5-8.5)
I 24 8.0 Onli, (7.4-8.9) 32 8.0 0.11 (7.4-8.8 )
J 3 8.4 0.18 (8.2-8.5) 8 7.8 0.25 (7.2-8.4)
K 9 7.8 0.19 (7.5-8.4) 7 7.9 0.31 (7.4-8.5)
ib 6 8.3 0.41 (7.8-8.9) if 8.0 0.39 (7.6-9.1 )
M 13 (ate 0.20 (7.1-8.0) 12 7.8 0.19 (7.3-8.5)
N 11 7.9 0.26 (7.0-8.7 ) 3 7.4 0.35 Cleiea)
O 1 8.0 a Cage ) 0 == at ( Ghee )
P 3 (65) 0.12 (7.4-7.6) 14 7.4 0.25 (7.2-7.8)
Q 1 7.6 (aca ) 0 oe Sp. (a
R 1 8.1 (ree ) 3 8.1 0.18 (7.9-8.2 )
Alveolar length of maxillary toothrow
A 6 9.0 0.37 (8.5-9.6) 10 8.7 O27 (8.2-9.4)
B 11 9.3 0.19 (8.7-9.8 ) 14 9.5 0.21 (8.8-10.0)
Cc 16 9.4 0.17 (8.7-10.1) 18 9.3 0.20 (8.5-10.1)
D 9 9.4 0.24 (8.6-9.8 ) 16 9.3 0.22 (8.6-10.1)
E 3 9.0 0.58 (8.5-9.5) 5 8.6 0.36 (8.2-9.1)
F 7 9.0 0.25 (8.5-9.4) 8 8.9 0.26 (8.1-9.2)
G 5 9.1 0.45 (8.6-9.9) 10 9.2 0.26 (8.7-9.9)
H 8 9.1 0.20 (8.7-9.6) 8 9.1 0.31 (8.4-9.7)
I 22, 9.4 0.20 (8.6-10.3 ) 9 9.1 Ol7/ (8.0-10.1)
J 4 9.1 0.19 (9.0-9.4) 8 8.9 0.22 (8.4-9.4)
K 8 9.3 0.27 (8.8-9.8 ) 7 9.1 0.28 (8.6-9.5)
IE- 6 9.7 0.34 (9.0-10.1 ) 8 9.4 0.34 (8.6-9.9)
M 13 8.5 0.25 (8.0-9.5) 12 8.7 0.33 (7.9-10.0)
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 97
TABLE 13.—Concluded.
Locality Males Females
Code N Mean = 2QSE Range N Mean =+ 2SE Range
N 10 8.7 0.27 (8.1-9.4) 3 8.5 0.75 (7.8-9.1 )
O il 9.2 ws (Gees ) 0 se paces US Coe Se
P 3 9.1 0.41 (8.8-9.5 ) 4 9.0 0.34 (8.6-9.4 )
Q 1 9.4 a (paki ate ) 0 le oe) ee
R 1 9.9 (Ca ae ) 3 9.8 0.58 (9.3-10.3 )
Length of palatal bridge
A 6 8.6 0.25 (8.3-9.1 ) 10 7.9 0.24 (7.1-8.4)
B 11 8.2 0.33 (6.8-8.9 ) 13} 7.9 0.23 (7.1-8.3 )
C 15 8.0 0.19 (7.3-8.5) 18 8.0 0.28 (7.1-9.5)
D 9 8.3 0.35 (7.7-9.0 ) 16 8.0 0.15 (7.4-8.5 )
E 3 7.9 0.23 (7.7-8.1) 5 es 0.20 (7.6-8.1 )
F 1 7.8 0.43 (6.9-8.4 ) 8 8.0 0.20 (7.5-8.4 )
G 5 8.2 0.60 (7.0-8.7 ) 10 8.0 0.34 (7.1-8.9 )
H Uf 7.9 0.19 (7.7-8.4) 8 7.9 0.32 (7.4-8.4)
I 24 8.1 0.17 (7.4-9.0 ) 33 8.0 0.14 (7.1-8.9 )
J 3 7.9 0.70 (7.2-8.3 ) 8 7.4 0.60 (7.0-7.9)
K 8 7.8 0.23 (7.2-8.2) i 7.8 0.35 (7.3-8.5 )
IL 6 8.4 0.51 (7.3-9.0) U 8.2 0.32 (7.8-9.1)
M 13 7.6 0.19 (7.0-8.1 ) 13 Uae 0.22 (6.9-8.1)
N 11 8.1 0.26 (7.2-8.9 ) 3 7.6 0.76 (7.0-8.3 )
O 1 8.6 ASO A A ) 0 fee. Ge = )
12 3 Wao 0.81 (6.8-8.2 ) 4 7.8 0.42 (7.5-8.4)
Q i 8.6 a (Hat ) 0 | ey (ee )
R 1 9.3 (eyes ) 3 8.7 0.31 (8.5-9.0)
Length of nasals
A 6 19.9 0.64 (18.8-20.8 ) 9 18.4 0.61 (16.9-19.4 )
B Bl 19.7 0.46 (18.0-20.7 ) He} 19.2 0.55 (AES=ZO 7p)
C 15 19.9 0.45 (625-2715) ILy/ 19.3 0.48 (HIGHEZTED))
D 9 20.1 0.55 (18.9-21.4) 16 20.3 0.30 (19.3-21.6)
E 3 18.3 PAIL (17.6-19.5) 4 18.7 I foyll (16.9-20.4 )
F 7 19.6 0.43 (18.5-20.2 ) 8 18.8 0.41 (18.0-19.7 )
G 5 19.7 0.77 (18.8-21.1) 10 19.2 0.54 (17.5-20.8 )
H 7 20.5 0.68 (19.5-22.0) 8 19.1 0.65 (17.6-20.6 )
I PALL 19.3 0.46 (16.6-20.8 ) 30 19.2 0.35 (17.8-21.0)
J 4 19.0 Tak) (17.4-20.0) 8 18.0 0.80 (16.4-19.8 )
K 9 19.0 0.44 (17.8-19.7) i 18.4 0.55 (17.6-19.4)
L 6 20.5 1.00 (18.6-22.0) 8 19.0 0.54 (17.8-19.9)
M 13 18.1 0.51 (16.3-19.2 ) 12, ie9) 0.60 (16.2-19.3)
N 1a 18.0 0.76 (16.1-20.3 ) 3 We 0.19 Goals)
O 1 17.9 (Se Gaae) 0 ee ae ( Gee)
P 3 17.9 0.35 (17.6-18.2 ) 4 7A 0.81 (16.3-18.2 )
Q 1 17.9 (2 ) 0 aa = (ae es)
R i 19.6 (ae ) 3 19.0 1.39 (17.9-20.3 )
lary toothrow deviates noticeably from
the anticipated trends. For example, sam-
ples such as L and D, are large and M
and N are smaller. Specimens from other
localities, such as P and K, have propor-
tionately longer toothrows, whereas those
from locality A are atypically short. The
patterns of variation in palatal bridge
length shown by sequence of means are
similar to those of toothrow length ex-
cept that specimens from locality P are
among the smallest. The pattern of vari-
ation in nasal length is similar to that
of rostral length.
The rank-order system of scoring
means described above was employed to
search for trends in size variation in N.
micropus. Specimens from localities D
(south-central Kansas) and L (coastal
Texas ) were thus calculated to be larger
98 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
than other specimens in the range of the
species. Moving away from locality D,
size decreases gradually but consistently
in specimens to the south (localities G,
H, and I) and west (localities C, B, and
A). Specimens from localities southwest
(localities F, E, O, and J) of the above-
listed seven localities decrease in size
clinally. The large area in central Texas
from which specimens of N. micropus
are absent (see Fig. 6 and discussion of
distribution for N. m. canescens) lies be-
tween locality I and the two in southern
Texas (K and L). It is possible that the
only route for gene flow between locality
L and I is through western Texas; or in
other words, animals from locality L may
be effectively isolated from the northern
populations of woodrats that they re-
semble in size. Specimens from locality
K are considerably smaller than those
from L, slightly smaller than those from
I and slightly larger than those from J.
Specimens from Coahuila (locality M)
are probably smallest of N. m. canescens,
but if so, they are only slightly smaller
than those from New Mexico and the
Big Bend area (J) of Texas. Specimens
of N. m. micropus from coastal Tamauli-
pas have proportionately longer tails,
and thus have high means for total length
and tail length. Cranially they are as
small or possibly smaller than those from
adjacent locality M. The single break in
the gradual cline in size is across the
lower Rio Grande River. Locality L,
having among the largest specimens of
the species, is contiguous with locality
N, which supports small woodrats having
relatively long and often unicolored tails
(N. m. micropus). The steepness of this
“step” in the cline decreases to the north-
west along the Rio Grande. For exam-
ple, specimens from locality K are con-
siderably smaller than those from L, but
considerably larger than those from M.
Farther west, specimens from Chihuahua
are indistinguishable from those in south-
west Texas.
Size relationships between specimens
of N. m. micropus from northern Tamau-
lipas and southern Tamaulipas (pre-
viously N. m. littoralis) demonstrate that
rats from the two localities are similar, |
especially with respect to external and.
cranial dimensions and, to a lesser extent,
color. I detect no real basis for con-.
tinuing to recognize littoralis as a sub-
species.
Because the only available “adult”
specimens from Rio Verde, San Luis
Potosi (planiceps, locality Q) and from
White Sands, New Mexico (canescens,
sample O, previously known as _ leu-
cophea) are of age-group V, comments
on size of these groups must be tentative.
However, woodrats from White Sands
appear to be nearly the same size as
other specimens from New Mexico. The
holotype of planiceps is similar in size to
other specimens of N. micropus from
Mexico.
On the basis of the four adult speci-
mens (one male, three females) of N.
angustipalata examined, it appears that
individuals of this species are much
larger than those of N. micropus from
all localities in Mexico. The only areas
from which specimens of N. micropus
compare favorably in size to individuals
of angustipalata are localities D and L.
The external measurements of angusti-
palata far exceed those of all samples of
micropus, and measurements of lengths
of all or parts of the skull are generally
larger. In measurements of breadth,
however, several samples of micropus
are larger than angustipalata (see table
13 for comparative measurements ).
Comparisons of sequence of means
and subset relationships from SS-STP
computations including the 13 samples
of N. floridana and 14 of N. micropus
together, reveal that floridana generally
is the larger (see Table 12 and Figs.
15-20). Samples of floridana from north-
western (campestris) and north-central
(attwateri) Kansas and those from south-
eastern Texas (rubida) are larger on the
average in most dimensions than samples
of micropus. Samples of attwateri from
southeastern Kansas and from both lo-
calities in Texas usually are larger than
samples of micropus; however, in some
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 99
dimensions, samples of micropus from
‘south-central Kansas and coastal south-
ern Texas are larger than one or more
of the floridana samples. Specimens of
micropus from the above two localities
and from localities in western Kansas
and northern Oklahoma are usually
larger than samples of baileyi, campestris
from Colorado, and attwateri from north-
eastern Kansas and eastern Oklahoma.
Specimens of micropus from Colorado,
extreme southwestern Kansas, southwest-
ern Oklahoma, and northern Texas are
nearly equal in size to specimens of the
last-mentioned samples of floridana. The
micropus from southern and western lo-
calities are consistently smaller than
woodrats of either species from other
localities. The single exception is tail
length in N. m. micropus, which exceeds
that of all other samples of N. micropus
and most samples of N. floridana. Wood-
rats from the panhandle of Texas, south-
western Texas, and non-coastal southern
Texas are intermediate in size between
specimens from farther to the south and
west and those from localities to the
north and east.
The general trends noted above are
less well marked in certain dimensions
than others; for example, least interor-
bital constriction is broader in all sam-
ples of floridana females than in any
sample of micropus females. The only
samples of micropus that occasionally
average larger than N. angustipalata are
those from south-central Kansas and
southern coastal Texas. However, cer-
tain samples of floridana (rubida, cam-
pestris from Kansas, and attwateri from
north-central Kansas) are larger than
angustipalata in many dimensions.
In conclusion, univariate analyses in-
dicate that the range of size variation
within the species micropus exceeds that
in the populations of floridana studied.
Also, variation in micropus tends to be
clinal and relatively consistent geograph-
ically. The single major exception is the
large size of specimens from coastal
southern Texas. Specimens of micropus
from western and southern localities gen-
erally are smaller than those from north-
ern and eastern localities, but those from
coastal Texas are larger on the average
than all samples of micropus from con-
tiguous localities and larger than most
samples from northern parts of the range
of the species. This phenomenon could
have resulted from one or more of three
distinct possibilities. The samples from
this locality consisted of less than 10 in-
dividuals of each sex, and the apparent
large size of these woodrats might be
the result of sampling error. I consider
this possibility relatively unlikely, how-
ever, because large size was evinced by
specimens of both sexes. The proba-
bility of sampling error involving two
samples from the same locality is much
lower than when only one sample is
involved. Secondly, specimens of flori-
dana from southern Texas are large; pos-
sibly the large size of micropus from
contiguous localities is the result of in-
trogression of genetic material from flori-
dana. Thus, the robustness of animals
from coastal Texas perhaps should be
interpreted as evidence for hybridiza-
tion. Thirdly, there is the possibility that
whatever selective forces have resulted
in large individuals of floridana in south-
ern Texas also are operating on adjacent
populations of micropus, resulting in the
unexpected large size. Evaluation of the
latter two possibilities is difficult and
must remain speculative until additional
data are available. If hybridization is
the answer, it might be expected that
specimens of floridana from southern
Texas would be slightly smaller than,
instead of slightly larger than, specimens
from northern Texas and southern Okla-
homa. However, it also must be remem-
bered that certain qualitative cranial
characters discussed previously indicated
that specimens of floridana from locali-
ties in southern Texas were relatively
more micropus-like than are those in
most other populations of floridana.
Multivariate Analyses of Mensural
Characters
Moss (1968) and Sokal and Michener
100 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
(1967) have shown that standardization
of character states to equally weight
characters greatly influences the cluster-
ing of OTU’s in correlation phenograms
and further tends to reduce the degree of
isolation of “aberrant” OTU’s. The dis-
tance phenogram usually is less influ-
enced by standardization of character
states. Comparisons by correlation and
by distance augment one another, and
must be considered simultaneously in the
interpretation of phenograms. Correla-
tions are relatively independent of size
(totally independent with unstandard-
ized character states) and cluster OTU’s
primarily on the basis of relative propor-
tions. On the other hand, distances are
less dependent on relative proportions,
and cluster primarily on the basis of ab-
solute differences between the numerical
values of characters. For example, when
Moss (1968:38) multiplied continuous
characters by a factor of two to create
hypothetical “giant? OTU’s and com-
pared original and “giant” OTU’s using
unstandardized data, the normal and
“giant” OTU’s clustered in the correla-
tion phenogram at the 1.0 level. How-
ever, in the distance phenogram based
on unstandardized data, there was com-
plete separation of normal and “giant”
OTU’s with comparable clustering within
each major cluster. Standardization of
the data resulted in a high frequency of
group clustering (a cluster of normal
OTU’s joined its respective cluster of
giant OTU’s) in the correlation pheno-
gram, but the distance phenogram was
altered very little by standardization.
As previously mentioned, character
states were standardized for all computa-
tions by CLSNT. In most cases I have
illustrated distance phenograms, and in
all cases the clustering relationships of
correlation phenograms are discussed to
emphasize proportional relationships and
absolute differences among the woodrats.
When woodrats from grouped localities
were compared using all of the available
characters, both correlation and _ dis-
tance phenograms are presented. A
certain amount of distortion results in the
clustering process from a multidimen-
sional correlation or distance matrix to a
two-dimensional phenogram. The coef-
ficients of cophenetic correlation, calcu-
lated to express correlation between the
original matrices and the resultant phe-
nograms, are given beyond for all phe-
nograms. This coefficient is normally
about 10 percent higher for distance
phenograms than for correlation pheno-
grams. Rohlf (1968) discussed various
relationships between results of cluster
analyses and those of principal compo-
nents. He recommended (1968:254) that
“numerical taxonomic studies should use
both cluster analyses and 3-D models in
order to extract and present as much in-
formation as is possible from the raw
data.” In all cases, I have analyzed prin-
cipal components in conjunction with
cluster analyses. Additionally, for each
projection of OTU’s onto the three prin-
cipal components, a minimally intercon-
nected network (Cavalli-Sforza and Ed-
wards, 1967) was computed from the
among-OTU distance matrix. When the
number of OTU’s was low, these have
been included on the 3-D drawings.
Models are presented as _ perspective
drawings; thus, with respect to the left
rear corner of a square platform, the
viewer is 0.3 units (one unit is equal to
the length of one side of the platform)
to the right, 3.0 units toward the front,
and at a height (the third principal com-
ponent) even with the OTU projected
farthest from the platform.
Neotoma_ floridana—A _ correlation
phenogram was computed from among-
OTU correlations for Neotoma floridana
females using means of the four external
and 10 cranial dimensions as character
states; the coefficient of cophenetic cor-
relation is 0.714. The 13 OTU’s (corre-
sponding to the 13 grouped localities
shown in figure 8) cluster into five major
groups, which are separated by correla-
tions of zero or negative values. Clusters
grouped females as follow: 1) localities
1 (N. f. baileyi) and 10 (N. f. attwateri
from southeastern Oklahoma); 2) local-
ities 2 and 3 (N. f. campestris); 3) local-
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 101
ities 4 (campestris), 5, 6, and 7 (attwa-
teri from Kansas ); 4) localities 8, 11, and
12 (attwateri from western Oklahoma
and Texas); and 5) localities 9 (attwa-
teri from northeastern Oklahoma) and 13
(N. f. rubida from southeastern Texas).
The coefficient of cophenetic correlation
between the distance phenogram and the
) respective matrix is 0.831 for the 13 sam-
ples of floridana females. As shown in
figure 21, four major clusters emerged;
the least distance between two major
clusters is 1.35.
The proportional relationships of
campestris females indicate that speci-
mens from Colorado and Nebraska are
most like other campestris from western
Kansas; but because of differences in size,
they are placed with attwateri in the dis-
tance phenogram. The large size of fe-
males from north-central Kansas (local-
ity 5) results in the separation of these
rats from other attwateri females in the
distance phenogram. The correlation in
size between sample means of attwateri
females from northeastern Oklahoma and
owonns -
12
13
a Oe
1.89 i209 0.69
those of rubida from southeastern Texas
was unexpected.
The correlation phenogram for flori-
dana males has a coefficient of cophenetic
correlation of only 0.699. Four major
clusters are separated from each other
by correlations of —0.02 or less. N. f.
campestris from localities 2 and 3 are in
the same cluster with baileyi. The sec-
ond cluster includes attwateri from Kan-
sas, campestris from locality 4, and
attwateri from the western sample in
Oklahoma. The two samples of attwateri
from eastern Oklahoma (9 and 10) are
placed in the third cluster with samples
12 (southern locality of attwateri in
Texas) and 13 (rubida). The sample of
attwateri from locality 11 is alone in the
fourth group, but anastomoses with clus-
ter three before these join the first two
clusters. The distance phenogram, which
has a coefficient of cophenetic correlation
of 0.816, has four clusters separated by
a distance of 1.25 or more (Fig. 21).
The most noteworthy differences in
the two phenograms for floridana males
1
B 2
6
9
il
10
3
4
5
8
vi
12
13
2.01 1,41 0.89
Fic. 21. Phenograms of UPGMA cluster analyses based on distance coefficients comparing stand-
ardized means of 14 mensural characters for 13 grouped localities of Neotoma floridana: A—females;
B—males. See text for coefficients of cophenetic correlation and see figure 8 for geographic areas
included within the coded localities.
102 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
involves the placement of rats from local-
ities 3, 11, and 13. Based on correlations,
sample 3 is most like samples 1 and 2,
sample 11 is most distinctive, and sample
13 is similar to sample 12. When the
emphasis is on differences (distance),
sample 3 is most like the larger attwateri,
sample 11 is similar to sample 9 and
other small attwateri; sample 13 is unlike
any other sample.
The first three principal components
account for 84.4 percent and 78.1 percent
of the total variation for females and
males, respectively. Percent variation in
each component for females and males,
respectively, is 63.4 and 48.6 in the first,
14.5 and 15.8 in the second, and 6.5 and
15.7 in the third. The 3-D perspective
drawings of projections of OTU’s (the
13 samples) onto the first three principal
components are shown in figure 22 for
both sexes.
The 3-D projection for females is
reminiscent of the cluster relationships
seen in the distance phenogram; the same
four basic groups obtain. Samples 5 and
13 are relatively isolated. Large campes-
tris (3 and 4) and large attwateri (7, 11,
and 12) are situated relatively close, and
baileyi and smaller campestris are near
the samples of small attwateri. The mini-
mally connected network shows the three
samples of campestris (2-4) intercon-
nected and connecting to the cluster of
smaller-sized females through sample 2
and the cluster of larger-sized females
through sample 4. Within the cluster of
“small” rats, baileyi is most distinct and
is connected to the rest of the samples
in the cluster through sample 10.
The 3-D projection of floridana males
also bears a strong resemblance to the
respective distance phenogram. In the
projection, sample 1 (baileyi) connects
through sample 2 to the cluster of large
attwateri and campestris. The group of
smaller attwateri connects to the “large”
group through sample 8. N. f. rubida is
farthest separated from other OTU’s and
connects to the group of larger rats
through sample 12, which is connected
to sample 8. Thus, sample 8 appears to
be more or less intermediate, serving to
interconnect the various clusters.
On the basis of mensural characters,
sample 13 (rubida) is the only sample
that clearly and consistently is distinct.
The females in sample 5 (north-central
Kansas) evince distinct differences from
either attwateri or campestris, and ap-
pear to be nearly as distinct as rubida;
this relationship is not seen in the com-
parison of males. The three samples of
campestris do not form a closely allied
group. In attwateri, a tendency exists
toward one cluster of smaller woodrats
and a second of larger woodrats. Geo-
graphically, however, localities from
which specimens of the two “groups”
originated are such that populations of
“small” and “large” rats are interspersed.
Animals from locality 12 (previously the
only locality from which specimens were
assigned attwateri) are much like mem-
bers of the “large” group of other attwa-
teri (previously osagensis) and do not
resemble rubida.
Neotoma micropus and Neotoma an-
gustipalata—Neotoma angustipalata is
treated with samples of N. micropus in
all CLSNT analyses. These two taxa
were combined because, on geographic
grounds, it appeared that angustipalata
might be a subspecies of micropus
(Hooper, 1953:10; Alvarez, 1963:453)
and that N. angustipalata and N. m.
planiceps might best be considered as a
single taxon.
The coefficient of cophenetic correla-
tion between the correlation phenogram
and matrix for the 15 samples of N. mi-
cropus and one sample of N. angusti-
palata females is 0.835. Two major clus-
ters are formed. The first consists of one
subcluster of samples A (Colorado and
Cimarron County, Oklahoma), F (Texas
panhandle) and E (New Mexico) and a
second subcluster that joins the first at
a correlation of 0.05. This subcluster in-
cludes samples J (Big Bend area of
Texas), K (non-coastal southern Texas ),
H (southwestern Oklahoma), I (north-
eastern Texas), B (southwestern Kansas
and adjacent Oklahoma panhandle), D
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA
103
I
Fic. 22. Three-dimensional perspective drawings of the projections of 13 samples (OTU’s) of
Neotoma floridana onto the first three principal components based on correlation among 14 mensural
characters: A—females; B—males. Dashed lines between OTU’s illustrate the minimally intercon-
nected networks computed from the respective among-OTU distance matrices.
See text for per-
centages of variation in each component and figure 8 for geographic areas included within the
coded localities.
(south-central Kansas), C (south-central
Kansas just west of locality D and ad-
jacent Oklahoma panhandle), and G
(northwestern Oklahoma south of local-
ity D). The second major cluster is com-
posed of samples L (southern coastal
Texas), R (N. angustipalata), M (Coah-
uila and Nuevo Leén), N (N. m. mic-
ropus from northern Tamaulipas) and P
(N. m. micropus from southern Tamauli-
104 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
pas). In essence, this phenogram places
all samples of N. m. canescens except
two (M and L) in a single major cluster
that is not highly correlated internally.
The other major cluster includes an array
of taxa including N. angustipalata, both
samples of N. m. micropus, and two sam-
ples (one of large woodrats and the other
of small woodrats) of N. m. canescens.
The distance phenogram (Fig. 23)
for micropus and angustipalata females
has a correlation of 0.820 with the dis-
tance matrix. If a distance of 1.25 or
greater is considered to separate major
clusters, four were computed. The pat-
tern of clustering seen in the distance
phenogram corresponds quite well to the
taxonomic arrangement of these two spe-
cies. That is, angustipalata appears most
distinct and is recognized at the specific
Oonoaonwnxzke- MS DP
> vz20rF tf =
SSS SS OO ——————————eeeeeeeeeee
2.065 1.365 0.665
level, and the two samples of N. m. mi-
cropus are distinct from those of other
micropus, but closer to them than to
angustipalata. The most variable sub-
species, canescens, consists of two groups
that correspond, with a few exceptions,
to the previously recognized boundaries
of N. m. canescens and N. m. micropus.
Nevertheless, both clusters include sam-
ples of woodrats previously assigned to
the two different names.
The coefficient of cophenetic correla-
tion for the correlation phenogram of 17
samples of micropus males and one sam-
ple of angustipalata males is relatively
high (0.849) for a correlation pheno-
gram. Of the three major clusters (sepa-
rated by a correlation of —0.05 or less),
one contains the two samples from New
Mexico (E and O); the second, joins
—-—n" ono wrroo09 PF
rmanoonmrsktvye2zx iu
eee ee eee eee
2.20 1.40 0.60
Fic. 23. Phenograms of UPGMA cluster analyses based on distance coefficients comparing stand-
ardized means of 14 mensural characters for 16 (females) and 18 (males) grouped localities of Neo-
toma micropus (A-Q) and N. angustipalata (R):
females; B—males. See text for coefficients of
cophenetic correlation and figure 8 for geographic areas included within the coded localities.
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 105
the first before these two join the third,
and includes all samples of canescens
from localities in the United States ex-
cept E, O, and K. The third major
cluster contains two distinct subgroups
that join at a correlation of only 0.12.
In the first subgroup are samples K and
M (both N. m. canescens). In the other,
samples N and P (both N. m. micropus )
join at a correlation of 0.62, and Q (N.
m. planiceps) joins R (N. angustipalata)
at 0.800. These two couplets anastomose
at a correlation of 0.45. This phenogram
illustrates the high proportional simi-
larities between angustipalata and plani-
ceps, the affinities between the two sam-
ples of the subspecies micropus, and
the complete intermixing of samples of
N. micropus from the northern part of
the range where two subspecies pre-
viously were recognized.
The distance phenogram for this
series of male samples is shown in figure
23. The coefficient of cophenetic corre-
lation between the phenogram and _ its
matrix is 0.840. There is a marked ten-
dency in both phenograms of males for
most samples of N. m. canescens ( excep-
tions were samples E, O, and M, espe-
cially) to cluster together; the two sam-
ples of N. m. micropus are always more
similar to one another than either is to
any other sample, but woodrats in sam-
ple M appear to be as near micropus as
canescens. The correlation between N.
angustipalata and N. m. planiceps is re-
markably high, indicating proportional
similarity. Although available material
indicates that angustipalata is much
larger than planiceps, it must be remem-
bered that the only known specimen of
planiceps is a young adult. The simi-
larities of samples O and E from New
Mexico are noteworthy because speci-
mens in sample O previously were recog-
nized as a distinct subspecies, N. m.
leucophea.
Principal components analysis for fe-
males extracted a total of 86.2 percent of
the variation (components one to three
composed of 55.1, 24.3, and 6.8 percent,
respectively). The 3-D drawing of
OTU’s projected onto the first three com-
ponents is shown in figure 24. Sample
R, as expected, is most distinct and iso-
lated from other OTU’s, especially on
the second component. Sample M serves
as the intermediate through which sam-
ples of N. m. micropus connect with
samples of N. m. canescens. The latter
are separated on the first component
(which is highly correlated with size),
but were similarly placed on the second
component.
The first three components for males
contain 56.1, 27.3, and 7.6 percent of the
total variation, respectively, for a total
extraction of 91.0 percent. The 3-D pro-
jection (Fig. 24) of OTU’s onto these
components placed angustipalata as the
most distinct OTU, connected to mi-
cropus through sample L. Neotoma mi-
cropus planiceps is the only other rela-
tively distinct OTU, but it is separated
much less on component two than is
angustipalata; planiceps connects to
other samples of micropus through sam-
ple P. In the projection, as in the dis-
tance phenogram, sample M appears to
share as many affinities with the subspe-
cies micropus as with canescens.
The 3-D projections of both sexes
elucidate the distinctiveness of angusti-
palata, and to a lesser degree, the dis-
tinctiveness of planiceps. The affinities
of sample L with the northern samples
of large N. micropus are evident. Like-
wise, the similarity of the two samples
of N. m. micropus from Tamaulipas, and
the intermediacy of woodrats from
Coahuila and Nuevo Leén between mi-
cropus and canescens are shown. Finally,
the projections document the absence of
any distinct steps in the clinal variation
in samples of N. m. canescens.
Simultaneous Treatment of Three
Species——When all samples of N. flori-
dana, N. micropus and N. angustipalata
were treated simultaneously in a multi-
variate analyses of 14 character states,
the results are surprising. The correla-
tion phenogram for the 29 samples of fe-
males has a coefficient of cophenetic cor-
relation of only 0.686, and is divided
106 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
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D ail | | |
ey = a at | Bayne =
y Y | | |
; | |
| | loadeeal
| wis
joie ll Je em Ty
/ | | | 3 |
| |
| oO.
| eu
Fic. 24. Three-dimensional perspective drawings of the projections of 16 (females) and 18
(males) samples of Neotoma micropus (A-Q) and N. angustipalata (R) onto the first three princi-
pal components based on correlations among 14 mensural characters: A—females; B—males. Dashed
lines between OTU’s illustrate the minimally interconnected networks computed from the respective
among-OTU distance matrices. See text for percentages of variation in each component, and fig-
ure 8 for geographic areas included within the coded localities.
into two primary clusters separated by a micropus with those of floridana and the
negative correlation (-—0.25). Most sur- marked alteration of the clustering rela-
prising is the intermixing of samples of tionships seen previously for samples of
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 107
floridana. Although clustering of sam-
ples of angustipalata and micropus is not
exactly as discussed above, it is notice-
ably less altered. The first major cluster
contains N. f. rubida, N. angustipalata,
the samples of small N. micropus, and
sample L. The two samples of N. m.
micropus form a highly correlated coup-
let (0.78) that anastomoses first with the
sample of angustipalata. The other ma-
jor cluster contains the remaining sam-
ples of both species arranged into four
subclusters. One of these consists only
of sample 7 and another is made up of
the three samples of smallest floridana
( baileyi and attwateri samples 9 and 10).
The two remaining subclusters include
samples of floridana and micropus ar-
ranged such that neither species appears
to be distinct.
Some geographically contiguous sam-
ples tend to cluster together and there
is a general tendency of samples of each
species to cluster in the same subgroups.
However, the deviations from these ten-
dencies are so great as to cause this phe-
nogram to bear little resemblance to the
classification used herein or to the gen-
eral conclusions based on univariate
analyses.
The placement of OTU’s in the dis-
tance phenogram for all samples of fe-
males (Fig. 25) is more nearly congru-
ent with previously discussed pheno-
grams, 3-D projections, and the classifi-
cation that I have proposed. Although,
some samples of floridana and micropus
appear together in one of the four major
clusters, in only one instance is a sample
of one species placed more closely to a
sample of the other than to a conspecific
sample. This exception was sample D.
The coefficient of cophenetic correlation
between phenogram and matrix is 0.736;
the first bifurcation is at a distance of
1.86 and each cluster thereby formed is
composed of two major subclusters.
The correlation phenogram for the
31 samples of males closely resembles
the two correlation phenograms for males
discussed above. It has a coefficient of
cophenetic correlation of 0.720 to the
correlation matrix. Three clusters are
separated from each other by negative
correlations. The most distinct of these
contains N. angustipalata in a couplet
with N. m. planiceps, N. f. baileyi in a
couplet with N. f. campestris from local-
ity 2, a couplet with the two samples of
N. m. micropus, and lastly a couplet with
two geographically contiguous samples
of N. m. canescens (K and M). The re-
maining two clusters are more highly
correlated than either is to the first. Sam-
ples from the five most southern localities
of N. floridana (9, 10, 11, 12 and 13) are
included in one cluster with sample H
(N. m. canescens from southwestern
Oklahoma). In the third, sample 4
(campestris) forms a couplet with sam-
ple A (canescens) in a subcluster includ-
ing sample L and northern samples of
canescens. Samples E, J, and O (canes-
cens from New Mexico and adjacent
southwestern Texas) form another sub-
cluster with sample 3 (campestris). In
the remaining subcluster, four samples
of attwateri (5, 6, 7, and 8) are placed
near a sample of canescens (1).
Those OTU’s that form highly corre-
lated couplets or clusters when treated
in the restricted samples usually tend to
cluster when the three species are treated
simultaneously. Similarly, samples that
appear highly distinctive when treated in
conspecific groupings usually retain at
least partial distinctness when all sam-
ples are treated together. However,
those samples that are neither especially
distinct nor highly correlated when
treated conspecifically, usually are un-
predictable in their clustering relation-
ships when the number of samples and
total amount of variation are increased.
The distance phenogram for 31 sam-
ples of males, which has a coefficient of
cophenetic correlation of 0.765, is shown
in figure 25. Three major clusters sepa-
rated by a distance of 1.5 or more are
evident. The two phenograms for all
samples of males of both species indicate
the distinctness of angustipalata as com-
pared to micropus and floridana. The
size relationships of micropus and _flori-
108 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
- A
A B B
A G
F Cc
vi 6
E 9
J 11
K H
N D
P L
B 3
Cc 4
G 5
H 8
I 7
6 10
8 12
9 1
10 2
1 13
74 F
L I
D J
3 K
4 N
7 P
11 M
12 E
R oO
5 Q
13 R
1.925 1225 0.525 2.16 1.36 0.56 —
Fic. 25. Phenograms of UPGMA cluster analyses based on distance coefficients comparing stand-
ardized means of 14 mensural characters for 29 (females) and 31 (males) grouped localities of Neo-
toma floridana (1-13), N. micropus (A-Q), and N. angustipalata (R): A—females; B—males. See
text for coefficients of cophenetic correlation, and figure 8 for geographic areas included within
the coded localities.
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 109
dana overlap sufficiently that mensural
characters alone do not segregate them
into separate major clusters. The larger
micropus tend to form conspecific group-
clusters which are near group-clusters of
larger floridana; smaller micropus tend
to cluster separately from samples of
smaller floridana. On some occasions
samples A, F, and K, which are from
localities geographically intermediate be-
tween large micropus and small micro-
pus, clustered with the large micropus
and smaller floridana; on other occasions,
they clustered with the small micropus.
The 3-D projections of all samples of
females and of all samples of males are
shown separately in figure 26. The mini-
mally connected networks were com-
puted but have been omitted from the
drawings to enhance determination of
relative positioning of the OTU’s. Pro-
jection of 29 OTU’s on the three com-
ponents for females results in a more
nearly complete separation of samples of
micropus and floridana than is seen in
the two phenograms for females. Be-
cause each OTU is necessarily connected
by the network directly to at least one
other OTU and all OTU’s are intercon-
nected, it is necessary that at least one
connection exist between a sample of
micropus and one of floridana. In this
instance two such connections exist.
Sample 9 (northeastern Oklahoma flori-
dana) connects to sample H (southwest-
ern Oklahoma micropus), and sample D
(south-central Kansas micropus) con-
nects to sample 7 (southeastern Kansas
floridana). All samples of N. micropus
are directly or indirectly interconnected
without involving a sample of floridana,
but floridana samples 1, 2, 6, 8, 9, and
10 are connected to other samples of
floridana through a series of samples of
micropus (9 to H to I to G to C to D
to 7). N. angustipalata connects only to
N. m. canescens sample L.
In the 3-D projection of males, only
the minimal number (two) of inter-
specific connections were computed.
Sample 9 is connected to sample H to
join micropus and floridana. Neotoma
angustipalata joins only to sample 13,
N. f. rubida. In the unconnected draw-
ing (Fig. 26), it can be seen that several
samples of micropus overlapped samples
of floridana on the first component. The
connections of these micropus samples
were G to A, and B to C to D to L. In
the 3-D projections for females there are
two distinct groups of floridana samples.
A tendency exists toward a similar sepa-
ration on the projections for males, but
it is less distinctly defined.
Multivariate Analyses of Size, Color,
and Qualitative Cranial Characters
Following multivariate analyses of
the 14 mensural characters discussed
above, similar analyses were conducted
using the same 14 mensural characters
together with four color reflectance
scores and three, scored, qualitative cra-
nial characters. Thus a total of 21 char-
acters was available for each sex of each
sample. Instead of analyzing sexes sepa-
rately as above, the 21 characters for
each were pooled and used as 42 char-
acters for each sample. For the two sam-
ples composed only of a single male spec-
imen each (O and Q), the 21 characters
were treated twice, once with those for
males and once with those for females.
Measurements of bacula or other charac-
ters were not included because data for
one or more samples were not available.
The results obtained depict the rela-
tionships of the various OTU’s in a more
comprehensive way than do interpreta-
tions based on separate analyses (by sex)
of mensural characters alone. However,
an understanding of the relationships
based only on mensural characters is
necessary to understand overall geo-
graphic trends in size and to determine
relative distinctness or indistinctness of
various taxa based solely on dimensions
and relative proportions.
Neotoma floridana—CLSNT based
on 42 characters as described above us-
ing the 13 samples of Neotoma floridana
yielded results congruent with the pres-
ent classification. The coefficient of co-
phenetic correlation is 0.727 between the
110 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
/
/
———
Fic. 26. Three-dimensional perspective drawings of the projections of 29 (females) and 31
(males) samples of Neotoma floridana (1-13), N. micropus (A-Q), and N. angustipalata (R) onto
the first three principal components based on correlations among 14 mensural characters: A—fe-
males; B—males. See text for percentages of variation in each component and figure 8 for geo-
graphic areas included within the coded localities.
correlation phenogram (Fig. 27) and the
matrix from which the phenogram was
computed. Two major clusters are sepa-
rated by a correlation of —0.24. This
phenogram, which was computed from
data on males and females, is remarkably
unlike the correlation phenogram dis-
cussed above for floridana females.
Despite several minor alterations, it re-
sembles the correlation phenogram of
floridana males. The relatively high cor-
relation between N. f. attwateri and N.
f. rubida is indicative of proportional
similarity of the two, and possibly re-
flects intergradation between the two in
southeastern Texas. The two samples of
N. f. campestris from western localities
(2 and 3) are also relatively highly cor-
related. Characteristics of campestris
from locality 4 are more highly correlated
with those of attwateri than with other
samples of campestris. In this pheno-
gram, balieyi appears more like cam-
pestris than attwateri.
The distance phenogram (Fig. 27)
for floridana is characterized by several
major shifts in the positioning of OTU’s
relative to that seen in the correlation
phenogram. These shifts affect primarily
the non-attwateri samples; samples 6, 8,
9, and 10 remain relatively close to-
gether and samples 7 and 11 remain to-
gether. Sample 12, which is highly corre-
lated to 13, is placed with two other
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 111
samples of attwateri, 7 and 11, in the
distance phenogram. Samples 4 and 5
are removed from a correlation cluster
with the “large” attwateri samples and
placed with sample 3. Sample 3 is clus-
tered with samples 1 and 2 in the correla-
tion phenogram. These two samples (1
and 2) remain together, but are sepa-
rated by an appreciable distance (1.15).
Sample 13 (rubida) is the most distinct
sample in the distance phenogram. The
coefficient of cophenetic correlation for
this phenogram is 0.769.
The first five principal components
were extracted in computations involv-
ing 42 characters. The percent variation
in these is 36.6, 22.6, 12.2, 9.8, and 5.1
for a total of 86.3 percent; 71.4 percent
of the variation is in the first three com-
ponents. The 3-D projection of the 13
OTU’s on the first three components
(Fig. 28) and the minimally connected
network (not figured) indicate that sam-
ple 7 is intermediate between other sam-
ples in many respects; five independent
subgroups interconnect by direct attach-
ment to sample 7. One subgroup consists
1
A 2
3
6
8
9
10
11
12
13
-0.30 0.10 0.50
only of sample 5 (sample 5 and 7 are
the two most distant directly-connected
samples of attwateri) and another only
of sample 11. A third subgroup includes
sample 12 relatively close and sample
13 at a considerable distance. Another
includes the four samples of small-sized
attwateri and the last includes the three
samples of campestris and one of baileyi.
The latter “lineage” is especially interest-
ing because neither the correlation nor
the distance phenogram placed the three
samples of campestris together. More-
over, the sequence of the connections is
4 to 3 to 2 to 1; geographically this cor-
responds east-west for the three samples
of campestris. The significance of the
apparent relationship between _ baileyi
and campestris will be discussed below
with respect to zoogeographic history.
Neotoma micropus and Neotoma
angustipalata—tThe correlation pheno-
gram for the 18 samples of N. micropus
and N. angustipalata (Fig. 29) has a
coefficient of cophenetic correlation of
0.815 and consists of three major clusters.
Placement of the five samples of small
13
[a
1.85 1.35 0.85
Fic. 27. Phenograms of UPGMA cluster analyses based on correlation (A) and distance (B)
coefficients comparing standardized means of 42 mensural, color, and scored cranial characters for
13 geographic localities of Neotoma floridana. See text for coefficients of cophenetic correlation, and
figure 8 for geographic areas included within the coded localities.
112 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
11
II
I
Fic. 28. Three-dimensional perspective drawings of the projections of 13 samples (OTU’s) of
Neotoma floridana (A) and 18 samples (OTU’s) of N. angustipalata and N. micropus (B, com-
pare with Fig. 30) onto the first three principal components based on correlations among 42 mensural,
color, and scored cranial characters. Dashed lines between OTU’s illustrate the minimally intercon-
nected networks computed from the respective among-OTU distance matrices. See text for percent-
ages of variation in each component, and figure 8 for geographic areas included within the coded
localities.
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 113
and pallid woodrats from New Mexico,
western Texas, Coahuila, and Nuevo
Leon in a single cluster seems reasonable
on an a priori visual basis. The inter-
mediacy of specimens from locality Kk
is indicated by the low correlation (0.16)
between that sample and other samples
from eastern and northern localities. As
in other phenograms reflecting both cor-
relation and distance, samples N and P
(N. m. micropus) cluster separately from
samples of N. m. canescens. Although
specimens of canescens from locality L
and specimens of angustipalata do not
resemble each other in general appear-
ance, these two samples are similar pro-
portionally. However, as previously dis-
cussed, they do not cluster together when
distances are emphasized.
The distance phenogram (Fig. 29)
>
ox p
Q©H w~zeareemnzsomrereeon oOo
eee Ee ———— ee
-0.24 0.16 0.56
for these 18 samples of woodrats is some-
what unique in that there are few small
group-clusters anastomosing to form
larger clusters; instead, there is a high
incidence of individual OTU’s sequen-
tially joining clusters composed of less
distinct OTU’s. The coefficient of co-
phenetic correlation between the pheno-
gram and the distance matrix is 0.891.
The distinctness of angustipalata is
again substantiated by the distance phe-
nogram, and N. m. planiceps appears
more distinct than indicated by results
of other analyses. It must be remem-
bered, however, that the latter “sample”
consists of a single young adult male.
This consideration is especially important
because characters of that one specimen
have been used for both males and fe-
males. Nevertheless, the results indicate
Oo oO OD Xt PP
ao vzsi=e 1 OM S| = oc =
———————— SS SSS SS
2.135 1.435 0.735
Fic. 29. Phenograms of UPGMA cluster analyses based on correlation (A) and distance (B) co-
efficients comparing standardized means of 42 mensural, color, and scored cranial characters for 18
geographic localities of Neotoma micropus (A-Q) and N. angustipalata (R). See text for coeffi-
cients of cophenetic correlation, and figure 8 for geographic areas included within the coded localities.
114 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
that planiceps is not especially similar to
samples of either N. m. micropus, or
N. m. canescens and should be recog-
nized as a distinct subspecies until more
specimens are available. Also, planiceps
did not cluster with angustipalata as has
been seen in some other analyses.
Clustering relationships indicate that
there is slight morphological basis for
recognizing two subspecies (as has been
done in the past) for the woodrats that
I have considered collectively under the
name N. m. canescens. Of the six sam-
ples most closely clustered, three pre-
viously were assigned to one subspecies
and three to another. Furthermore,
placement of samples F, J, and K in the
various phenograms and 3-D projections
together with results of univariate analy-
ses clearly indicate that any subspecies
boundary merely would divide the wood-
rats into two groups from some arbitrarily
selected place within a series of partially
discordant clines.
Principal components analysis of
these 18 samples considered 87.2 percent
of the total variation when five compo-
nents were extracted. Percents of varia-
tion in the first five components con-
sidered sequentially are 37.2, 30.3, 9.5,
5.7, and 4.5. When projected onto the
first three components (Fig. 28), which
contain 77 percent of the total variation,
the results are similar to those seen in
the distance phenogram. The impression
of close relationship among the six sam-
ples of N. m. canescens from northern
and eastern localities in the range is
maintained; samples D, L, and K con-
nect directly to this “cluster” but do not
connect directly to each other. Sample
R (angustipalata) constitutes the most
distinctive OTU and connects only to
sample L. Sample M, which serves as
an “intermediate”, connects to sample
K, then serves to connect samples E and
O on one “lineage”, F and J on a second,
and N on a third. Sample N connects
first to sample P and at a much greater
distance to sample Q (planiceps).
The placement of OTU’s and the con-
nections shown by the minimally con-
nected network of the 3-D projection for
N. micropus is congruent with the no-
menclatorial arrangement of these wood-
rats proposed here. Figure 30 illustrates
the placement of OTU’s on the first and
second components better than can be
seen in the 3-D drawing (Fig. 28). This
figure represents a two-dimensional scat-
ter-diagram of the OTU’s on these two
components; the three-dimensional mini-
mally interconnected network has been
added together with the distance coef-
ficients from the original distance matrix
for all directly connected OTU’s. In
viewing this figure it should be noted
that discrepancies between apparent and
computed distances separating OTU’s
are accounted for in the third dimension,
which is illustrated in figure 28.
Neotoma angustipalata, recognized as
a distinct species, is well separated to the
left and to the front of the plotting sur-
face on figure 30. Furthermore, angusti-
palata is not connected to any of the
samples of micropus from geographically
contiguous localities. N. m. planiceps is
well separated from all other OTU’s,
especially on the second component, and
connects only to a sample of N. m. mi-
cropus from adjacent Tamaulipas. The
two samples of N. m. micropus are
closely placed on the first and second
principal components and are situated in
a position nearly intermediate between
the nearest OTU’s, representing canescens
and planiceps. They connect directly to
planiceps and to the sample of canescens
from adjacent Nuevo Leén and Coahuila.
The remaining OTU’s all representing
samples of canescens, are placed in a
single “cluster”, showing the trend _ to-
ward smaller individuals in the south-
western parts of the range (samples E,
O, J, and M) and the intermediacy of
samples F and K.
Simultaneous Treatment of Three
Species——The correlation phenogram
that was computed when the 42 charac-
ter states of the 31 samples (all three
species ) of woodrats were treated simul-
taneously is shown in figure 3l. This
phenogram has a coefficient of cophe-
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 115
De...
as C 0.42 =
0.56 »° & 0.57 &
fe H
Bee 0 48° ; je 0.74 %
E s
. Gl” A E1EOO
ee ae o e N
Saas 0 © al :
¢ ‘ ‘
oi e ;
y @?
ue \ 0.66 :
a wa
xs ‘ ef
i \ 0.99 97%
a eX Wa ya wy)
‘ OR ! 1
ie SG OEE (dorsal.
i Te, H Z \ Oo
af . ees Ce)
/ poss é 0.81
; :
aS
/ 1.58 /
/ /
At u¢
Pe Ui
5 i
II v a
Ge Hi 107,
/ ae
GA ¢:
We yy
ise Be
we N/ 0.66
OR veP
/
ri
/
!
t
/
'
!
!
‘
/ 1,31
'
L
‘
i
J
I
1
4
'
'
'
<2
I
Fic. 30. Two-dimensional drawing of the projections of 18 samples (OTU’s) of Neotoma micropus
(A-Q) and N. angustipalata (R) onto the first two principal components based on correlations among
42 mensural, color, and scored cranial characters. Dashed lines between OTU’s illustrate the min-
imally interconnected networks computed from the among-OTU distance matrices. Distance coeffi-
See text
cients from the distance matrix are given for each pair of directly connected localities.
for percentage of variation in each component, and figure 8 for geographic areas included within the
coded localities (nominal taxa are shown with distinctive symbols). This figure should be compared
with figure 28B.
cies, with the obvious exception of the
netic correlation of 0.863 with the corre-
lation matrix. The major separation at a placement of N. f. rubida.
correlation of —0.325 separated all sam- The distance phenogram (Fig. 31)
ples of N. floridana into one cluster and for computations on samples of the three
all samples of N. micropus with the species simultaneously has a coefficient
single sample of N. angustipalata into of cophenetic correlation of only 0.714
the other. This phenogram corresponds to the distance matrix. This is unusually
well with results seen in 3-D projections low compared to the coefficient (0.863)
for the correlation phenogram and ma-
and in distance phenograms for both spe-
116 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
R R
A L B 1
N 6
P 8
Q 9
A 10
H 7
8 11
Cc 12
G 2
i 3
K 4
E 5
ry) 13
M A
F B
J Cc
D G
1 t
2 H
3 D
4 K
5 L
7 E
11 M
12 tr)
13 F
6 J
8 N
9 P
10 Q
-0.325 0.175 0.675 1.74 1.14 0.54
Fic. 31. Phenograms of UPGMA cluster analyses based on correlation (A) and distance (B) co-
efficients comparing standardized means of 42 mensural, color, and scored cranial characters for 31
geographic localities of Neotoma floridana (1-13), N. micropus (A-Q), and N. angustipalata (R).
See text for coefficients of cophenetic correlation, and figure 8 for geographic areas included within
the coded localities.
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 117
trix; normally the highest coefficient is
for distance. Four major clusters are
seen in the distance phenogram. At the
first bifurcation, all samples of micropus
are placed together in two clusters. Neo-
toma angustipalata forms a third “clus-
ter” by itself that connects at a distance
of 1.53 to the fourth major cluster (com-
posed of the 13 samples of N. floridana).
Within the floridana cluster, two OTU’s
(5 and 13) are relatively distinct; this
was expected for sample 13 (rubida) but
I anticipated that sample 5 (attwateri
from north-central Kansas ) would cluster
either with other samples of attwateri or
with samples of campestris. The three
samples of campestris form a distinct
cluster, and baileyi appears relatively dis-
tinct, but joins the samples of smaller
attwateri before they are joined by the
samples of larger attwateri.
Of the two major clusters of N. mi-
cropus, one consists of the 14 samples of
N. m. canescens and the other of the two
samples of N. m. micropus along with
N. m. planiceps. The two samples of
N. m. micropus join at a distance of 0.63,
and planiceps joins that couplet at a dis-
tance of 1.02. In the distance phenogram
shown in figure 29, canescens from local-
ity M appears more like samples of N.
m. micropus than like other samples of
canescens; in the large phenogram, sam-
ple M is placed with other samples of
canescens. In both phenograms, the
small, pallid woodrats from New Mexico,
western Texas, and adjacent Mexico tend
to form a relatively homogeneous and
distinct subgroup. This relationship is
seen also when OTU’s are projected onto
principal components. I considered the
possibility (see introductory remarks in
the account of N. micropus above) of
applying the available name N. m. leu-
cophea to those woodrats from localities
E, F, J, M, and O. However, there are
no indications of well marked “steps” in
clines of variation, and no apparent past
or present geographic or physiographic
barriers. Because there seems to be no
way to designate a meaningful boundary
between the two potential taxa, this ar-
rangement was rejected.
Principal components analysis on the
character correlation matrix extracted
50.1, 15.9, 7.8, 6.6, and 3.9 percent of the
variance for the first five principal com-
ponents, respectively. Of this, 73.8 per-
cent is in the first three components. A
three-dimensional drawing of the 31
OTU’s projected onto the first three com-
ponents is shown in figure 32. The mini-
mally connected network has been omit-
ted from the 3-D projection but is given
in figure 33, which shows two two-dimen-
sional scatter diagrams wherein the 31
OTU’s are projected onto components
one and two (33A) and one and three
(33B). The three drawings considered
simultaneously show undistorted spatial
relationships of the OTU’s on the prin-
cipal components and further elucidate
the congruency between the results of
these analyses and the nomenclatorial ar-
rangement I have applied to the wood-
rats.
Samples of micropus and floridana
are completely separated on the first
component, although micropus sample
L nearly overlaps floridana samples 1
and 2. Also on the first component,
angustipalata is placed with floridana
and widely separated from micropus.
Neotoma floridana rubida is placed to
the left of other samples of floridana on
that component, and the samples of small
southwestern N. m. canescens are placed
to the right of the samples of larger
northern and eastern canescens.
On the second component, samples of
N. f. campestris are separated from other
samples of floridana. Sample 5 (attwa-
teri from north-central Kansas) is be-
tween samples of campestris and those
of other attwateri, but on a tangent rela-
tive to the first component. This sample
of attwateri (5) and the sample of baileyi
(1) both are connected to other samples
of attwateri, but not to samples of cam-
pestris or to each other. In part, this pro-
jection implies that baileyi might best be
considered as the same taxon as attwateri
( baileyi is the oldest available name and
would be the valid name for all if this
118 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
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Fic. 32. Three-dimensional perspective drawing of the projections of 31 samples (OTU’s) of
Neotoma floridana (1-13), N. micropus (A-Q), and N. angustipalata (R) onto the first three princi-
pal components based on correlations among 42 mensural, color, and scored cranial characters. See
text for percentages of variation in each component, and figure 8 for geographic areas included
within the coded localities. This figure should be compared with figure 33.
was done). Neotoma angustipalata is
distinctly separated from samples of flori-
dana on the second component. When
samples of N. micropus are considered,
it can be seen that the second component
separates samples P and N (N. m. mi-
cropus) and sample Q (planiceps) in one
direction and sample E (canescens from
the Texas panhandle) in the other; re-
maining samples are similarly placed on
these two components.
The third component further sepa-
rates angustipalata from all samples of
floridana and clearly demonstrates the
distinctiveness of micropus samples D
and L from floridana samples 1, 2, 6, and
9. On both the first and second compo-
nents, these six samples are placed in
relatively close proximity. From the dis-
tance matrix, it can be seen that the
separation between D and 2 is 1.15, that
between L and 8 is 1.04, that between
L and 6 is 1.05, and that between L and
2 (which appear especially close on the
3-D projection) is 1.16. In the minimally
connected network, only two intercon-
necting lines (the minimal number) con-
nect OTU’s of different species. Neotoma
angustipalata is connected to N. f. attwa-
teri sample 7 at a distance of 1.58, and
N. m. canescens sample D is connected to
N. f. attwateri sample § at a distance of
0.94.
With the exceptions of a relatively
high degree of distinctiveness in attwa-
teri sample 5, the apparent affinities of
baileyi with attwateri, and the relative
distinctiveness of samples of canescens
from southwestern localities, the classifi-
cation I have employed is in accord with
the results of this principal components
analysis. It clearly shows that angusti-
palata is phenetically distinct and that
floridana and micropus are morphologi-
cally distinct and should not be consid-
ered conspecific. The distinctiveness of
119
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA
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N. f. campestris and N. f. rubida as com-
pared to contiguous samples of N. f. at-
twateri can be seen also. Similarly, N. m.
micropus and N. m. planiceps are shown
to be clearly distinct from N. m. canes-
cens. There appears to be some basis for
recognition of another name (N. m. leu-
cophea) for specimens from New Mexico,
western Texas, and adjacent Mexico; the
question that arises is basically a matter
of one’s concept of the limits of a sub-
species.
Were Neotoma floridana baileyi and
N. f. attwateri geographically contiguous,
I would consider them a single taxon.
However, baileyi clearly is isolated, and
has been shown to share nearly equal
affinities with campestris. Furthermore,
it is relatively unique with respect to
qualitative cranial characters. Therefore,
I think it best to continue to recog-
nize baileyi as subspecifically distinct.
To consider those rats from locality 5
(north-central Kansas) as a new subspe-
cies on the basis of their uniqueness in
the distance phenogram and 3-D projec-
tion just discussed would be, in my esti-
mation, a gross error. The sample from
that area is small and there is no reason
to believe that the population of wood-
rats there represents a truly distinctive
evolutionary unit. It is possible that the
large size and apparent distinctiveness of
woodrats from the narrow zone of sec-
ondary intergradation between campes-
tris and attwateri reflect some effect ( pos-
sibly heterosis) of recent hybridization.
There is some basis for naming as a
distinct subspecies those large and rela-
tively distinct populations (L) of mi-
cropus from southern coastal Texas. They
are different from woodrats in adjacent
Tamaulipas (and herein are assigned to
different subspecies), but study and sta-
tistical analysis of all available specimens
from southern Texas indicate that the
pattern of variation to the north and west
from coastal Texas is clinal and that
woodrats from locality K (non-coastal
southern Texas ) show varying degrees of
intermediacy between those from locality
L and those from localities J, I, and M.
Discriminant Function Analysis
Discriminant function analysis has
been employed by Lawrence and Bossert
(1969) to distinguish dog-coyote hy-
brids; these authors (1967) also were
able to identify skulls of wild canids with
this relatively sophisticated technique.
Anderson (1969:44) conducted a pre-
liminary discriminant analysis to dis-
tinguish specimens of Neotoma micropus
and N. albigula; he found that members
of the two species could be separated
better in this way than by factor analysis.
I have used discriminant function
analysis (MULDIS) to compare indi-
vidual specimens of woodrat taxa as fol-
lows: Neotoma floridana baileyi with N.
f. attwateri; N. f. campestris with N. f.
attwateri; N. f. campestris with N. m.
canescens; and N. f. attwateri with N.
m. canescens. In some cases, specimens
from geographically intermediate sam-
ples, suspected hybrids, or laboratory-
bred hybrids were included as a third
group for comparison with reference
samples. In one instance, only the ref-
erence samples were compared. These
analyses were conducted to determine:
1) if the nominal taxa are sufficiently and
consistently distinctive at the level of the
individual in the 10 cranial dimensions,
four color reflectance scores, and three
scored qualitative characters so that dis-
criminant analysis could distinguish
members of the different taxa by differ-
entially weighting characters to accentu-
ate existing differences; 2) if known hy-
brids between floridana and micropus
could be distinguished by use of the dis-
criminant technique; 3) if discriminant
scores of suspected hybrid individuals
would be similar to those of known hy-
brids; and 4) if a series of discriminant
multipliers could be calculated from
identified reference samples so that fu-
ture material could be identified by mul-
tiplying the values of the same 17 char-
acters by the discriminant multipliers
and then summed to compare discrim-
inant scores. The characters used in these
analyses have been described previously.
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 121
Males and females of Groups VI-VIII
were treated together. In addition to
the calculations of values previously
mentioned, MULDIS also computed the
“best” placement of each individual in
the original reference samples and indi-
cated the number, if any, that would
“best” have been included in the other
reference sample.
In comparisons of N. f. baileyi and
N. f. attwateri, 18 specimens of baileyi
from several localities within the range
of the subspecies were compared with
36 specimens of attwateri from localities
6-10. Because baileyi is geographically
isolated, there are no suspected natural
hybrids or geographic intermediates and
discriminant scores for a “test” sample of
laboratory hybrids were not computed.
Although there is no overlap between
the discriminant scores of the two sub-
species (Fig. 34), one specimen of attwa-
teri is more like the reference specimens
of baileyi than like other specimens of
attwateri. The mean and range (in
parentheses ) of discriminant scores from
attwateri and baileyi, respectively, are
14.20 (12.32-16.85) and 18.87 (17.47-
20.92). When the single “wrongly
placed” specimen of attwateri was re-
moved, the upper extreme of that sam-
ple was reduced to 15.82. From the list
of discriminant multipliers computed for
these two taxa (Table 14), it can be seen
that measurements of interorbital con-
striction, breadth of the rostrum, length
of the nasals, and morphology of the
sphenopalatine vacuities best serve to
distinguish baileyi from attwateri. Only
condylobasilar length and length of max-
illary toothrow were weighted at espe-
cially low levels.
These results indicate that baileyi and
attwateri are generally distinguishable at
the level of the individual, but that a
few individuals of one taxon may closely
resemble members of the other morphol-
ogically. As previously discussed, most
skulls of baileyi can be identified by the
three scored cranial characters included
in the discriminant function analysis. Of
these, only one (sphenopalatine vacui-
ties) was weighted relatively high. Re-
flectance values were computed by anal-
ysis of variance and SS-STP to be signifi-
cantly different between baileyi and at-
twateri, but for some reason, probably
because of the high within-group vari-
ance, these scores are not weighted no-
ticeably higher than cranial dimensions.
A frequency histogram showing sepa-
ration of the reference samples of N. f.
campestris and N. f. attwateri together
with the projection of four specimens
from locality 5 (all from Ellsworth
County, Kansas) is shown in figure 35.
No overlap between the two samples is
observed and all specimens are “best”
considered in the sample with which they
were originally placed. The mean and
extreme (in parentheses) discriminant
scores for the 36 specimens of attwateri
(localities 6-10) and 27 specimens of
campestris (localities 2-4), respectively,
are 13.64 (11.05-15.32) and 18.66 (16.35-
20.66). The discriminant multipliers cal-
culated for the comparisons are shown
in table 14. That for rostral breadth is
especially high and those for reflectance
of blue and green are relatively high.
Color reflectance was expected to be
heavily weighted, considering the differ-
ences in color between members of the
two subspecies. Several characters are
weighted relatively low, especially con-
dylobasilar length.
Within the attwateri reference sam-
ple, there is a slight but noticeable ten-
dency for the discriminant scores of spec-
imens from localities farthest from the
range of campestris to be least like those
of campestris. Furthermore, within the
campestris reference sample there exists
an obvious tendency for specimens from
locality 4 (adjacent to the range of
attwateri) to cluster toward the attwateri
reference sample. The specimen of
campestris (KU 119700) with the second
lowest discriminant score (17.11) is from
a locality in Russell County, Kansas, only
one mile west of the Russell-Ellsworth
County boundary, which I have con-
sidered the general line of demarcation
between the two races. Discriminant
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WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 123
Frequency
12.5 13.5 14.5 15.5 16.5
17.5 18.5 19.5 20.5 21.5
Discriminant Score
Fic. 34. Frequency histogram of discriminant scores computed by discriminant function analysis
comparing individuals of Neotoma floridana attwateri (6-10) and N. f. baileyi (1). See figure 8 for
geographic area of origin, indicated by numerals on the histogram, of each specimen.
scores of two of four specimens from just
east of this line are intermediate between
the extremes of the two reference sam-
ples. Although the scores of the other
two are within the extremes for attwateri,
they are near the campestris side of the
histogram.
As determined by these analyses, N.
f. campestris and N. f. attwateri are con-
sistently distinct at the level of the indi-
vidual. The area of presumed secondary
intergradation apparently includes both
Russell and Ellsworth counties, Kansas,
because specimens from this area tend
to have convergent, albeit distinct, dis-
criminant scores. Additional specimens
from the relatively narrow zone of con-
tact between the two taxa might reveal
Frequency
Discriminant Score
Fic. 35. Frequency histogram of discriminant scores computed by discriminant function analysis
comparing Neotoma floridana attwateri (5-10) and N. f. campestris (2-4). Solid lines enclose in-
dividuals that were included in the two reference samples, whereas dashed lines enclose individuals
of attwateri (5) from a geographically intermediate area whose scores were computed on the basis
of discriminant multipliers computed during comparison of the reference samples. See figure 8 for
geographic area of origin, indicated by numerals on the histogram for each specimen.
124 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
overlap of discriminant scores on the
histogram between the two_ reference
samples.
The histogram showing frequency of
discriminant scores for 41 Neotoma mi-
cropus canescens, 27 Neotoma floridana
campestris, and 11 laboratory-bred hy-
brids is shown in figure 36. Mean and
extreme (in parentheses) scores for
canescens and campestris are, respec-
tively, -12.33 (-14.20 --9.31) and -5.53
(—7.82 - 3.80). In each reference sam-
ple, one individual has a discriminant
score that approaches the scores of the
other species, but in both instances the
specimens are “best” included with the
conspecific reference sample. With these
two individuals included, the reference
samples are separated by 1.49 units,
whereas without them the separation
would have been 3.71 units. As noted
above, specimens of campestris from lo-
cality 4 tend to have scores that are more
like those of attwateri than are the scores
of specimens from localities 2 and 3. A
similar relationship is not observed when
campestris is computed against canes-
Frequency
cens. Discriminant multipliers computed
for the 17 characters are given in table
14. One cranial dimension, interorbital
constriction, is weighted especially heav-
ily. This undoubtedly results from the
previously discussed (see account of qua-
litative cranial characters) differences in
the morphology of the interorbital region.
All three scored cranial characters are
weighted relatively heavily, but only
morphology of the sphenopalatine vacui-
ties is given an absolute multiplier value
greater than unity, indicating that differ-
ences in the vacuities between the two
races are more consistent (less variance )
than differences in the anterior spine and
posterior margin of the palate. Reflec-
tance of red and green and the summa-
tion of all reflectance readings are
weighted low, but the reflectance value
for blue is computed an above average
discriminant multiplier.
Discriminant scores were computed
for 11 laboratory-bred hybrids and pro-
jected onto the histogram. Of five indi-
viduals of the first filial generation (F1),
two have scores in the same frequency
Discriminant Score
Fic. 36. Frequency histogram of discriminant scores computed by discriminant function analysis
comparing Neotoma floridana campestris (2-4) and N. micropus canescens (B-D). See figure 35 for
significance of solid and dashed lines. Fl and F2 indicate laboratory-bred hybrids between the
two taxa of the first and second filial generations, respectively. F3 denotes a back-cross individual
whose non-hybrid parent was an N. f. campestris. See figure 8 for geographic area of origin, indi-
cated by numerals and letters on the histogram, for other specimens.
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 125
class as the “aberrant” individual of
campestris discussed above. The other
three have scores between the extremes
of the canescens reference sample. These
results are somewhat surprising, because
I had expected F1 hybrids would fall in
the 3.7 unit zone between the two refer-
ence samples. Considering the results of
discriminant analysis of Fl hybrids, the
scores of specimens from the second filial
generation (F2) are about as expected.
Again there is a tendency for the scores
to be more like those of canescens than
those of campestris. The range of varia-
tion is slightly greater than that of F1’s,
and the range of variation is less than
that seen for the two reference samples.
Only one adult (of 30 weeks of age or
more) back-cross individual was avail-
able. This woodrat (F3), the progeny
of an F1 hybrid mated to a campestris,
has a discriminant score of —7.52, which
placed it within the campestris range on
the histogram.
The separation between N. f. cam-
pestris and N. m. canescens is adequate
to demonstrate that the two can be dis-
tinguished by discriminant analysis. In
the absence of the two extreme indi-
viduals, the separation would have been
relatively great considering the small
number of characters used and the close
relationship of the two species. How-
ever, larger samples probably would
show that the two specimens discussed
are not “aberrant,” but rather near the
extremes of discriminant scores of the
two taxa compared.
Reference samples of 36 N. f. attwa-
teri from localities 6-10 and 41 N. m.
canescens from localities B-D were used
to compute discriminant multipliers in
comparisons of these two taxa. Mean
and extreme (in parentheses) dicrim-
inant scores for individuals of the refer-
ence samples were 12.77 (10.29-14.98)
for attwateri and 19.54 (17.34-21.56) for
canescens. All individuals of both sam-
ples were computed to be in the “cor-
rect’ sample; when discriminant scores
were plotted on a frequency histogram
(Fig. 37), none of the members of either
reference sample had deviate scores re-
sulting in placement in a class disjunct
from other classes of the species.
As shown in table 14, rostral breadth
again is weighted relatively heavily.
Other characters that appear to differ
consistently between the two taxa are
interorbital constriction, sphenopalatine
vacuities, and color reflectance of blue.
The summated reflectance score (total)
was given a multiplier value of 0.0, and
thus was of no use in distinguishing in-
dividuals of N. f. attwateri and N. m.
canescens. Mastoid breadth also was
shown to be of little value in distinguish-
ing members of the two taxa. Discrim-
inant scores of 40 woodrats from a variety
of sources were computed and projected
onto the frequency histogram (Fig. 37)
with scores of specimens in the two ref-
erence samples. This test group is com-
posed of the following specimens: 1) 12
laboratory hybrids of the first filial (F1)
generation; 2) six hybrids of the second
filial (F2) generation; 3) two back-cross
hybrids resulting from the mating of F1
hybrids with micropus (M3); 4) eight
specimens that I had previously identified
as micropus (S1) from the locality of
sympatry of the two reference taxa (3
mi S Chester, Major Co., Oklahoma);
5) four specimens that I had previously
identified as floridana (S2) from the lo-
cality of sympatry; 6) five specimens
previously identified as natural hybrids
from that locality (S3); 7) and three
specimens from 8.9 mi S Aledo (14 mi
SW Fort Worth), Parker Co., Texas (T),
that did not appear to be typical repre-
sentatives of floridana.
Six of the Fl hybrids have discrim-
inant scores between the extremes of the
scores of the parental species, as was
expected for all. Five of the other six
have scores that were near the lower end
of the range of N. m. canescens, but the
score of the sixth is like that of typical
canescens. Most F1 hybrids apparently
tend to be intermediate in the 17 char-
acters employed, but somewhat more
like micropus than floridana. Second
generation hybrids (F2) are, on the aver-
126 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
Frequency
15.2
Discriminant Score
Fic. 37. Frequency histogram of discriminant scores computed by discriminant function analysis
comparing Neotoma floridana attwateri (6-10) and N. micropus canescens (B-D). See figure 35 for
significance of solid and dashed lines and see figure 8 for geographic area of origin, indicated by
symbols on the histogram, for most specimens. Those not included in figure 8 and their identifying
symbols (in parentheses) are as follows: laboratory-bred hybrids between the two taxa of the first
and second filial generations (Fl and F2, respectively); laboratory-bred back-cross hybrids whose
non-hybrid parent was N. m. canescens (M3); specimens from 3 mi S Chester, Major Co., Okla-
homa, that had been identified previously as N. micropus, N. floridana, or hybrids (S1, $2, and $3,
respectively ); and specimens from 8.9 mi S Aledo, Parker Co., Texas, that were suspiciously atypical
in color (T).
age, slightly more micropus-like than are
Fl hybrids, and also are more variable.
The score of one approaches the upper
extreme of micropus scores; that of an-
other approaches the most micropus-like
floridana scores. None overlapped the
scores of floridana. One of the two back-
cross specimens (M3) demonstrates no
perceptible affinities for floridana, but
the score of the other is similar to those
of F1 hybrids.
Considering animals from natural pop-
ulations, the three suspiciously-colored
specimens from Parker County, Texas,
all have discriminant scores typical of
floridana. The scores of two are above
the mode for the floridana reference sam-
ple and one is near the upper extreme;
none could be identified as “hybrid” or
“intergrade” on the basis of discriminant
scores. The scores of seven of the spec-
imens from the area of sympatry that
had been identified as micropus (S1) are
typical of the scores of reference mi-
cropus. The score of the eighth (17.68),
however, is larger than that of only one
individual in the micropus reference sam-
ple, and thus similar to scores of labora-
tory-bred Fl hybrids. All four of the
specimens identified as N. floridana (S2)
have scores within the extremes of ref-
erence floridana. One, in fact, is near the
lower limit for floridana, but two others
have scores slightly above the mode.
Of greatest interest is the placement on
the histogram of scores of the five speci-
mens identified as natural hybrids; all
have scores between the extremes of the
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 127
two reference samples and are in fre-
quency classes with known FI and F2
hybrids.
These results show that laboratory
reared hybrids between N. floridana and
N. micropus tend to have discriminant
scores intermediate between those of
non-hybrids, but when not intermediate
they are more like micropus than flori-
dana. Second generation hybrids again
appear to be more variable and also
more micropus-like than F1_ hybrids.
Backcross hybrids, as expected, tend to
be either intermediate or more like their
non-hybrid parent. Woodrats from the
known area of sympatry in northern
Oklahoma may be similar to members
of either species, or they may be inter-
mediate. Results of discriminant func-
tion analysis further substantiate conclu-
sions by Spencer (1968) and by me that
the two species interbreed at the locality
of sympatry. In addition, it can be seen
that identifications based on visual anal-
ysis of pelage and cranial characteristics
are highly reliable, as indicated by re-
sults of discriminant function analysis.
Although the series of specimens from
Parker County, Texas, near the western
edge of the range of the species in north-
ern Texas, are suspiciously grayish, spec-
imens from that locality are either typical
floridana or at least much more like flori-
dana than micropus.
It appears that discriminant function
analysis is a sophisticated statistical tool
that has tremendous potential in studies
of geographic variation, especially in lo-
cating zones of marked morphological
change (see Rees, 1970, for comparable
results in studies of white-tailed deer),
and for distinguishing natural hybrids.
However, the observed tendency for
floridana-micropus F1 and F2 hybrids to
be more like micropus than floridana in-
dicates that hybrids of known ancestry
(laboratory-bred) should be used as
“controls” whenever possible in discrim-
inant analyses to determine where na-
tural hybrids likely will score relative to
the scores of the parental species.
NON-MORPHOLOGICAL CHARACTERS
COMPARATIVE REPRODUCTION
In view of the emphasis placed on
“reproductive isolation” in the biological
species concept (Mayr, 1965:19), studies
of reproductive patterns and habits con-
stitute a major aspect of investigations of
closely related taxa. It has been sug-
gested (erroneously I think) that evi-
dence of hybridization among animals
having internal fertilization implies con-
specificity. As presently understood,
laboratory experiments in hybridization
merely provide an indication of the pres-
ence, absence, or efficiency of isolating
mechanisms, especially postmating mech-
anisms (see Mayr, 1963:92). Brand and
Ryckman (1969) demonstrated a clear
understanding of this concept in their
interpretations of studies on Peromyscus.
Hybridization in natural habitats is more
often indicative of conspecificity, but as
stated by Mayr (1969:195) “allopatric
forms that hybridize only occasionally in
the zone of contact are full species.” In
fact, populations that have diverged mor-
phologically during isolation often hy-
bridize when geographic contact is re-
established until such time as selection
has established isolating mechanisms or
reinforced incipient mechanisms (Key,
1968). Premating isolating mechanisms,
such as habitat isolation, clearly are
tenuous forms of isolation, but they may
be sufficiently effective to prevent loss of
species integrity as a result of hybridiza-
tion. The emphasis on reproductive iso-
lation would seem better placed on the
abilities of taxa to maintain their respec-
tive specific integrities rather than on the
production of hybrids. Nevertheless,
studies of hybridization both in the labo-
ratory and the field often serve as im-
mensely useful indicators of animal rela-
tionships.
Breeding Cages——Two cages were
128 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
constructed especially for breeding
woodrats in the laboratory. Each was 60
by 60 by 18 inches with a #-inch plywood
floor and hinged top. The sides and top
were of }-inch hardware cloth secured
on the inside of a wooden frame. Two
other cages constructed for other pur-
poses were found to be excellent breed-
ing cages. These were 60 by 18 by 18
inches with }-inch plywood floors and
sides, and with hinged tops of hardware
cloth on wood frames. Internally, these
cages were constructed so that remov-
able hardware cloth partitions on wood
frames could be inserted at one-foot in-
tervals. The partitions had sliding metal
doors allowing woodrats to be separated
or penned together easily and without
handling. When these four cages were
in use, an upright rack of four metal
cages, 48 by 24 by 18 inches, frequently
was converted into two “two. story”
breeding cages by replacing the metal
trays that served as the floor of the upper
and third (from the top) cages with
trays 24 by 24 inches. Attempts to breed
woodrats in unconverted cages, 48 by 24
by 18 inches, and the smaller 24 by 24
by 18 inch cages never were successful
and often resulted in death of one of
the rats.
Recognition of Breeding Readiness.
—External indications of breeding con-
dition for both sexes were described by
Rainey (1956:605-609) for Neotoma
floridana, and by Raun (1966:14-17) for
N. micropus. In breeding males the
testes become noticeably enlarged and
scrotal; the swollen convoluted cauda
epididymis forms a conspicuous bulge
(Linsdale and Tevis, 1951:354), and the
skin of the scrotum appears thinner,
more darkly pigmented, and less haired
than in nonbreeding males. In both the
field and the laboratory it was noted that
these characteristics are somewhat more
easily discernible in breeding floridana
males than in breeding micropus males.
Also in floridana, the testes often descend
farther into the scrotal sac than do the
testes of micropus males. Healthy adult
laboratory males of both species had ap-
parently viable sperm in the epididy-
mides and testes throughout the year,
even when the testes were abdominal
and reduced in size. In sexually inactive
females, the vulva is imperforate and
cornified, the clitoris is small and white
or pinkish, and the teats are small.
Breeding females are easily distinguished
by a turgid, perforate vagina and an en-
larged, vascularized clitoris.
Age at Sexual Maturity—Both male
and female woodrats born early in spring
usually appear to be in breeding condi-
tion by late summer. The testes of young
males are smaller than those of adults
and the cauda epididymis protrudes less;
both the epididymides and testes contain
sperm. Several attempts were made to
place first-year males of micropus with
adult breeding females, but each attempt
was necessarily terminated to prevent
the male from being killed. A first-year
floridana male was placed with an adult
female floridana from 8 August until 4
September 1967; although the two were
compatible, they were never observed to
display sexual interest nor to copulate;
no litter resulted. The same male sired
several litters during the 1968 and 1969
breeding seasons.
In late summer of 1968, two first-year
females of each species were placed with
adult males of their own species for more
than two weeks each, but no young was
born to either. One of three subadult
female N. f. baileyi (Table 15), obtained
in late August of 1968, was nursing three
young judged to be less than two weeks
of age; the other two females were
neither pregnant nor lactating. At least
occasional females bear young in the
natural environment late in the season
of the year in which they are born.
Brown (1969:538) found that female
Neotoma mexicana born in the first lit-
ters of spring (April and May) normally
produce litters in June and July, often
while still at least partially in juvenile
pelage. This clearly is not the case in
either N. floridana or N. micropus. Young
of both sexes born as late as August were
consistently successful breeders in the
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 129
laboratory by March of the following
year.
Breeding Seasons.—As indicated by
age composition of samples of N. micro-
pus and as reported by Raun (1966:14),
breeding takes place throughout the year
in southern populations of the species,
with only a slight tendency for season-
ality. Females in northern populations
of micropus (Spencer, 1968:45, and Fin-
ley, 1958:486; Tables 15 and 16) appar-
ently begin breeding in December and
January, produce at least two and prob-
ably three litters before July, and some
females have an additional litter and
possibly two between early August and
the end of October. Neotoma floridana
in Kansas (Tables 15 and 16; Rainey
1956:609-613) begin breeding in Febru-
ary and females bear their first litters in
March or April and their second in May
or June. Most females are appreciatively
less active reproductively in July, then
have an additional litter in August or
September with occasional litters being
born as late as October. As indicated in
tables 15 and 16, the first litter of female
N. f. baileyi is born in April, a second in
June, and a third in July or August. I
doubt that baileyi produces litters after
mid-September, but available data do
not preclude the possibility. Late sum-
mer and autumn breeding in both species
may involve mostly young females born
earlier that year.
Estrous Cycle —Techniques described
by Chapman (1951:269) and Zarrow et
al. (1964:36-37) for determination of
estrus by examination of cells lining the
vagina were attempted early in my
TABLE 15. Reproductive status of adult and subadult Neotoma floridana and N. micropus females
captured in Nebraska, Colorado, Kansas, and Oklahoma from September, 1966 to April, 1969.
Number
progeny
Number collected
Date progeny born _ with female
Locality Date litter
( county ) captured Age bom ottot eae) oS Oe Remarks
Neotoma floridana baileyi
Cherry 31 Mar. Adult 13 Apr. 2 2
Cherry 31 Mar. Adult 9 Apr. 2 2 =
Cherry 31 Mar. Adult f =: . No litter born
Cherry 31 Mar. Adult 26 Apr. 2 2
Cherry 31 Mar. Adult 6 Apr. DD 1 iz
Cherry 31 Mar. Adult Died 17 Apr.;
had 3 resorbing
embryos
Cherry 31 Mar. Adult 16 Apr. 1 3 z
Cherry 24 Aug. Subadult No litter born
Cherry 24 Aug. Adult Killed 29 Aug.;
had 4 embryos
< 45 mm.
Cherry 24 Aug. Subadult Killed 29 Aug.;
not pregnant
Rock 21 Aug. Subadult 1 2 Killed 29 Aug.;
not pregnant
Rock 22, Aug. Subadult Killed 29 Aug.;
not pregnant
Neotoma floridana campestris
Logan 29 Aug. Adults (2) No litters born
Logan 29 Aug. Subadult Died 8 Sept.;
not pregnant
Ness 4 Sept. Subadult Killed 4 Sept.;
not pregnant
130 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
TABLE 15.—Continued.
Number
progeny
Number collected
Date progeny bom with female
Locality Date litter
( county ) captured Age born od ee) Jd 2° Remarks
Ness 4 Sept. Subadult Killed 13 Sept.;
not pregnant
Finney 5 Sept. Subadult Killed 5 Sept.;
not pregnant
Finney 5 Sept. Adults (2) Killed 5 Sept.;
neither pregnant
Finney 5 Sept. Subadults (5) a é- Killed 13 Sept.;
none pregnant
Finney 5 Sept. Adults (4) as = Killed 13 Sept.;
none pregnant
Hodgeman 8 Sept. Adult Killed 13 Sept.;
not pregnant
Ellis 18 Dec. Adults (9) No litters born
Ellis 18 Dec. Adults (2) Killed 18 Dec.;
neither pregnant
Ellis 19 Dec. Adults (2) Killed 21 Dec.;
neither pregnant
Russell 21 Dec. Adult Killed 21 Dec.;
not pregnant
Russell 21 Dec. Adults (4) Killed 13 Jan.;
none pregnant
Russell 21 Dec. Adult No litter born
Neotoma floridana attwateri
Major 31 Jan. Adult 10 Feb. 2 0 = is
Major 3 Jan. Adult es a = = No litter born
Douglas 3 Mar Adult 10 Mar. 2 1
Douglas 10 Mar. Adult 6 Apr. 1 3 =
Douglas 10 Mar. Subadult re No litter bor
Douglas 10 Apr. Adult 0 2 Killed 11 Apr.;
not pregnant
Major 7 June Adult Killed 7 June;
had 4 embryos
a a 7 Tague
Number Number Number Mean Mode per
matings successful Percent progeny litter litter attempted
Females attempted matings success of size size mating
N. f. baileyi X
N. f. attwateri 1 100.0 il 2 3.0 3 3.00
TOTAL 3 2 66.7 3 4 3.5 3-4 233
N. f. campestris X N. f. attwateri males
N. f. campestris 2) 1 50.0 2 1 3.0 3 1.50
N. f. campestris X
N. f. attwateri I 0) 0.0 = fe? =e se 0.00
TOTAL 3 1 Soo 2) 1 3.0 3 1.00
N. f. baileyi X N. m. canescens males
N. f. baileyi 1 1 100.0 2; @ 4.0 4 4.00
N. m. canescens (2) 1 0 0.0 gst ins! — A 0.00
TOTAL 2; 1 50.0 2) 2 4.0 4 2.00
N. f. campestris X N. m. canescens males
N. f. campestris X
N. m. canescens 6 2 BiB 8) 2 2 2.0 oD, 0.67
N. f. attwateri X
N. m. canescens 1 1 100.0 0) 2 2.0 2 2.00
TOTAL o 3 42.9 2 4 2.0 2, 0.86
N. f. attwateri X N. m. canescens F,; males
N. f. campestris 1 0 0.0 a mh an 0.00
N. m. canescens (2) 4 2 50.0 2 1 15 1-2 0.75
N. f. campestris X
N. m. canescens 3} 2 66.7 2 3 QS 2-3 1.67
N. f. attwateri X
N. m. canescens F, 6 2 Bie Eee) 3 2 2-5 2-3 0.83
LO MATE 14 6 42.9 0 6 22, 9) 0.93
N. f. attwateri X N. m. canescens F» males
N. f. attwateri Il 1 100.0 1 2; 3.0 3 3.00
N. f. attwateri X
N. m. canescens F2 0 0.0 _ ae eats we: 0.00
TOTAL 2 il 50.0 1 2 3.0 3 1.50
N. m. canescens X (N. f. attwateri X N. m. canescens ) male
N. f. campestris X
N. m. canescens 1 0 0.0 0.00
All Neotoma floridana males
N. floridana 63 31 49.2 49 Dik Sip 3 1.59
N. micropus DD 10 45.5 1L9/ WG 3.4 4 IES
Species-hybrids 3 2, 66.7 2 3 QD 2-3 1.67
TOA 88 43 48.9 68 fal 3.2 3 1.58
All Neotoma micropus males
N. floridana 31 u 22.6 10 9 2.7 2-3-4 0.61
N. micropus 38 9 Sh 14 10 2a 3 0.63
Species-hybrids 2, 1 50.0 2 1 3.0 3 1.50
TOTAL rial W7f 23:9 26 20 ell 3 0.65
All species-hybrid males
N. floridana 3 2 66.7 3 4 3.5 3-4 2.33
N. micropus 5 2 40.0 2 1 1.5 1-2 0.60
Species-hybrids 18 i 38.9 ih 9 23 2 0.89
TOTAL 26 11 42.3 12 14 2.4 } 1.00
142 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
TABLE 18.—Concluded.
Progeny
Number Number Number Mean Mode per
matings successful Percent progeny litter litter attempted
Females attempted matings success loftos conte) size size mating
All non-hybrid males
Same species 101 40 39.6 63 61 3.1 3 1323
Other species 53 17 32/1 27 26 3.1 4 1.00
Species-hybrids 5 3 60.0 4 4 OM | 3 1.60
TOTAL: 159 60 Sia 94 91 Bip 3 1.16
All males
All females 185 Hl 38.4 106 105 3.0 3 1.14
a male of the same race. Minima and
maxima frequently were 33 to 36 days.
No clearcut differences were observed
in gestation periods of the two species
either by me or by Spencer (1968). Ap-
parently the gestation period normally
fluctuates from 32 to 38 days with a
modal duration of 35 days. Post-partum
estrus and prolonged gestation appar-
ently occur in both species, but the fre-
quency of this phenomenon is not well
known and the physiology associated
therewith has not been investigated.
Size of Litters. —Literature pertaining
to litter size of Neotoma floridana has
been summarized by Rainey (1956:613).
In most populations that have been
studied, females regularly produced lit-
ters of one to four; occasional litters of
five have been reported. Modal litter
size for the species is three and the mean
usually is near three. Litter size of N.
micropus (Asdell, 1964:279) is appar-
ently slightly smaller. Feldman (1935:
301, 302) studied members of this species
from Carlsbad, New Mexico; each of 11
litters consisted of two young and in
each litter both progeny were of the
same Sex.
Size of litters born to females of the
northern N. f. baileyi in the laboratory
was slightly greater than those of any of
the other woodrats, as evinced both by
the mean (3.5) and the mode (four).
Litter size of the other two subspecies
of N. floridana and that of N. m. canes-
cens are comparable, having means near
3.0 and modes of three. ‘Two litters born
to N. f. baileyi X N. f. campestris “hy-
brid” females had only two progeny each.
This may indicate some type of partial
sterility, but more observations would be
necessary to draw meaningful conclu-
sions. The single litter born to an N. f.
baileyi X N. f. attwateri “hybrid” female
was the same as the modal litter size
(three) of floridana females; a male of
this cross sired a litter of four when
mated to a baileyi female.
Litter size of species-hybrids was no-
ticeably lower than that of either of the
parental species. Considering all mat-
ings involving at least one species-hy-
brid, modal litter size both of males and
of females was only two and the mean
for both was 2.4. Because hybrid males
sired only four litters with non-hybrid fe-
males and hybrid females produced only
five litters from matings with non-hybrid
males, it was not possible to determine
unequivocally from the data whether lit-
ters of hybrids are smaller because of
partial sterility in both sexes or only in
one. However, it can be seen in tables
17 and 18 that no hybrid female pro-
duced a litter of more than three young,
whereas one hybrid male sired a litter of
four when mated to a floridana female.
Of the 71 litters born as a result of labo-
ratory matings, only two consisted of a
single progeny; one of these matings was
between a hybrid male and a micropus
female. Mean litter size of non-hybrid
females bred to hybrid males was 2.5
whereas that of the reciprocal was 2.7.
Matings involving two hybrid individuals
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 143
averaged only 2.3 progeny per litter, pos-
sibly indicating that hybrids of both sexes
are less fertile than non-hybrids.
Table 15 provides additional informa-
tion on litter size and seasonal patterns
of reproduction. Data presented in table
16 give further information on litter sizes
and the reproductive season over a wide
geographic area. Litter sizes of floridana
and micropus may vary geographically,
with more northerly populations having
larger litters. In N. f. baileyi the mean
was more than 3.5 and the mode was
four progeny per litter; these data are
based on successful matings in the labo-
ratory, parturiation of previously con-
ceived litters in the laboratory, and em-
bryo counts recorded on specimen labels.
All parameters studied indicate that N.
f. campestris, N. f. attwateri, and north-
ern populations of N. m. canescens most
frequently have litters of three young
each and that the mean usually is near or
only slightly greater than three. South-
ern populations of canescens most fre-
quently have litters of two progeny as
seen in table 16 and reported by Raun
(1966:17) and Baker (1956:286).
The correlation between latitude and
litter size of mammals has been observed
previously (Lord, 1960, and others) and
probably has been best explained by
Spencer and Steinhoff (1968), who ex-
panded the theory originally put forth
by Lack (1948, 1954). Individuals of
northern populations have shorter breed-
ing seasons and can place more progeny
in subsequent generations by exerting
more “energy” per litter on large litters,
whereas those in southern populations
are most successful by conserving
“energy expended per litter and produc-
ing more litters with each containing
fewer individuals. In the woodrats
studied, at least, information discussed
previously regarding breeding seasons
further substantiates the hypothesis.
Sex Ratios at Birth—Sex ratios of
progeny of all rats studied appear to be
the typical one to one relationship. The
only sample that deviates significantly
(P <0.05, tested by Chi-square) is the
26 males to 12 females born to N. micro-
pus females that were pregnant when
captured; four of 11 litters consisted only
of male offspring. However, among
young micropus collected with adult fe-
males there were more females than
males and when the two samples are
considered together the number of males
only slightly exceeds the number of fe-
males.
Reproduction in Neotoma angusti-
palata—Information on the reproductive
habits of N. angustipalata is limited.
Hooper (1953:9) reported two nursing
young collected with a female on 19
May, and an adult female (Table 16)
contained a single embryo when ob-
tained in July. Two juveniles (UNAM
2166 and 2167) were collected on 6
October.
Discussion and Conclusions—Repro-
ductive habits of N. floridana and N.
micropus vary both intra- and_ inter-
specifically. In the primary study area,
the first litters of micropus are born two
or three weeks prior to the first litters of
floridana, but the breeding seasons of the
two species are otherwise approximately
the same. Laboratory and field observa-
tions conducted by me, and Spencer
(1968) show that the two species do
hybridize, and that hybrid progeny are
somatically and reproductively viable.
However, hybridization results in partial
hybrid sterility, as evinced by reduced
litter size. Reproductive isolation is at
best incomplete between the two species
and they probably will hybridize at all
localities of sympatry, at least until selec-
tion has had sufficient time to establish
and reinforce a mechanism of reproduc-
tive isolation. Only a single area of sym-
patry is presently known and the re-
sultant hybrid zone (see account of N.
m. canescens above) has not increased
in size during the five years that it has
been under observation. Furthermore,
no conslusive evidence exists to indicate
that the hybridization in north-central
Oklahoma is introgressive or that intro-
gression has occurred elsewhere along
the potential zone of contact between
144 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
the two species. Reproductive and distri-
butional evidence indicate that the two
species may be in an allopatric phase of
speciation as described by Key (1968),
wherein dynamic tension zones, such as
the mixed population in north-central
Oklahoma, are formed prior to establish-
ment of full reproductive isolation.
COMPARATIVE SEROLOGY
The dependency of protein synthesis
on genetic control indicates that physico-
chemical and immunological characteris-
tics of protein macromolecules are phe-
notypic expressions of the genotype.
Comparative study of proteins, therefore,
serves as an important means of studying
the relationships of animals (Florkin,
1964; Boyden, 1964). Evolutionary rates
of serological characters undoubtedly are
stochastic (Kirsch, 1969), as are those
of most characters.
Starch Gel Electrophoresis of
Hemoglobins
Electrophoretically demonstrable var-
iation in mammalian hemoglobins has
been the subject of much study recently.
In the Carnivora, hemoglobins appear to
be relatively stable even at the ordinal
level (Seal, 1969), whereas in the Chir-
optera variation has been reported at
the familial and generic levels ( Mitchell,
1966; Valdivieso et al., 1969). Hemo-
globin ionographs of primates (Neel,
1961; Ingram, 1963; Hill and Buettner-
Janusch, 1964; Sullivan and Nute, 1968)
and rodents (Johnson, 1968; Foreman,
1960; and others) have been shown to
vary intraspecifically in many taxa. Ad-
ditionally, Foreman (1964) discovered
by tryptic hydrolysis that in the genus
Peromyscus some _ electrophoretically
identical hemoglobins are chemically
distinct.
Birney and Perez (1971) reported
multiple hemoglobins in Neotoma flori-
dana, N. micropus, and laboratory-bred
hybrids of the two species. They ob-
served major bands of four migration
rates, designated (from slowest to
fastest) 1’, 1, 2, and 3, and several minor
bands that were not studied. Based on
the number and position of major elec-
trophoretic bands, seven distinctive he-
moglobin patterns or phenotypes were
described and labeled A through G as
follows (Fig. 39): “A” occurred only in
micropus and consisted of band 1 with
a leading diffuse zone that terminated in
a minor band at position 3; “B” was ob-
served in both species and in hybrids and
consisted of bands 1 and 2 and a leading
diffuse zone; “C”, observed only in flori-
dana and hybrids, was composed of
bands 1, 2, and 3; “D” consisted of bands
2 and 3 with a trailing diffuse zone and
also was limited to floridana and hybrids;
“E” was seen only in micropus and hy-
brids and was composed of bands 1’ and
2 with a long leading diffuse zone and a
terminal minor band; “F” was observed
only in floridana and consisted of a heavy
band, considered to be band 1, preceded
by a short diffuse zone; “G” was observed
only in laboratory-bred hybrids and con-
sisted either of bands 1’, 2, and 3 or of
all four major bands.
Results of electrophoresing precipi-
tated globins by the urea—veronal
method of Chernoff and Pettit (1964) in-
dicated to Birney and Perez (1970) that
the electrophoretically demonstrable var-
iation resided in the beta (8) chains of
ORIGIN
1 aa ea
wo a | aw
3
& | 2 me = = — a
a3) —— a a r=]
4 ace
a, B c D E F G
Phenotypes
Fic. 39. Diagrammatic representation of
electrophoretic patterns (phenotypes) of hemo-
globins of Neotoma floridana and N. micropus.
Major bands are represented by solid rectangles
and minor bands by horizontal lines. The cath-
ode is indicated by a minus sign and the anode
by a plus sign. See Bimey and Perez (1971)
for photographs of starch gels showing electro-
phoresed woodrat hemoglobins.
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 145
the hemoglobin molecules. They further
proposed tentative models that explained
the inheritance patterns observed and
demonstrated a possible sequence for the
evolution of multiple beta loci in the spe-
cies studied. According to the model,
multiple beta loci have arisen by gene
duplication so that at least three such
loci (probably closely linked) now are
present in floridana and at least two exist
in micropus. Neotoma micropus may
have either a third locus for production
of the beta peptides of molecules forming
band I’, or genes producing these pep-
tides may be allelic with those producing
the beta peptides seen in band 1. “Alleles”
that produce no peptide (termed 8° al-
leles) apparently are present at all beta
loci. These non-functional alleles may be
either deleted areas on the chromosomes
or they may be areas that are physically
present but under control of modifier
genes, or for other reasons do not con-
tribute a peptide chain. If modifier
genes are involved, it is likely that the
minor bands result from limited produc-
tion of the same peptides that form major
bands when the £ locus involved is fully
active.
Materials and Methods.—Studies of
hemoglobin samples discussed here were
conducted simultaneously with those re-
ported by Birney and Perez (1971). De-
tailed methods were outlined in that re-
port and are only summarized here.
Samples of whole blood were suspended
in a trisodium citrate anticoagulate,
washed three times in phosphate buf-
fered saline, and lysed in distilled water.
Hemoglobin phenotypes were deter-
mined by horizontal starch-gel electro-
phoresis in sodium borate buffer. Gels
were sliced and stained in a solution of
amido black in water-methanol-glacial
acetic acid. The iodoacetimide method
described by Riggs (1965) was em-
ployed to determine that none of the
observed bands resulted from polymer-
ization. Laboratory-bred woodrats are
not included in the discussion of hemo-
globin variation presented here because
they would tend to bias the frequency
of various phenotypes in favor of the
phenotype(s) of their parents.
Results and Discussion.—F requencies
of the seven hemoglobin phenotypes ob-
served in natural populations of Neotoma
floridana and N. micropus are shown in
table 19. At the time ancestral popula-
tions of floridana and micropus consti-
tuted a single species, it would appear
that only hemoglobin bands 1 and 2 were
present. These two bands are common
to both species and when they occur to-
gether to form phenotype B, the patterns
of the two species are essentially indis-
tinguishable. When band 1 occurs with-
out band 2 (phenotypes A and F), it is
heavier; the band migrates slightly
slower in floridana, and has a longer
leading diffuse zone in micropus. The
major band probably is formed by the
same, or only slightly modified, peptides.
The single banded situation may be the
primitive hemoglobin phenotype for the
two species, or phenotypes A and F both
may have been secondarily derived after
the two species were isolated. In any
event, it appears that 6! and 2 both
were present at the time of isolation be-
cause both were expressed by some indi-
viduals of the two species from every
locality from which I have a sample of
three or more individuals.
The B' and £° alleles apparently
originated in populations of micropus
and floridana, respectively, after the two
incipient species were geographically iso-
lated. Although both alleles are present
in the sample of woodrats from 3 mi S
Chester, Major Co., Oklahoma, they have
not been observed together elsewhere;
B' is not known for floridana nor is £3
known for micropus. If the 8" allele
ever was present in floridana, or if B?
ever was present in micropus, they have
been lost secondarily or exist in those
species in extremely low frequency.
It is not known whether the genes
controlling production of the beta chains
of molecules forming bands | and I’ are
alleles of a single locus or if they occur
at separate loci. Similarly, it is not known
with certainty what phenotype results
146
MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
TABLE 19. Frequency, expressed in percent, of seven hemoglobin phenotypes at selected
localities of Neotoma floridana and N. micropus.
Hemoglobin Phenotype
Origin of samples N A B C D E F G
Neotoma floridana baileyi
Cherry Co., Nebraska 17, 5.9 52.9 41.2
Rock Co., Nebraska 2 MP 50.0 50.0
All localities 19 5s3 52.6 42.1
Neotoma floridana campestris
Logan Co., Kansas 3 66.7 33.3 ae
Finney Co., Kansas 6 66.7 33.3
Ness Co., Kansas 3 100.0 aes.
Hodgeman Co., Kansas 2 oe 100.0
Ellis Co., Kansas 4 100.0 as =
Russell Co., Kansas 1G 5.9 35.3 58.8 ei
All localities 35 40.0 22.9 ob By
Neotoma floridana attwateri
Ellsworth Co., Kansas 4 75.0 _ 25.0
Douglas Co., Kansas 13 76.9 23h bea
All localities 1 76.5 17.6 5.9
Neotoma floridana
All localities (0) 39.4 29.6 28.2 2.8
Neotoma micropus canescens
Baca Co., Colorado 29 10.3 20.7 69.0
Hamilton Co., Kansas 9) 50.0 50.0
Haskell and Stevens
cos., Kansas 22 18.2 40.9 40.9
Meade Co., Kansas 6 = 50.0 50.0
Barber Co., Kansas 13 = 46.2 53.8
All localities 72 ia Jon nae 55.6
Neotoma from 3 mi S Chester, Major Co., Oklahoma
Specimens morphologically
like N. micropus 40.0 40.0 20.0
Specimens morphologically
like hybrids 8 12S 25.0 12.5 50.0
All specimens 13 Ae a 15.4 23.1 38.4
when both genes are present (Birney
and Perez, 1971). Therefore, it is not
possible to calculate their frequency ac-
curately. Moreover, no micropus has
been observed that lacked both bands
1 and J’, but breeding data presented by
Birney and Perez indicate that the °
allele also occurs in low frequency at
the 1-81 locus(i) in that species, as it
does in floridana. A crude estimate of the
frequency of 8! and £"’ can be calculated
by the Hardy-Weinberg formula, if it is
assumed that 8! and £"’ are allelic, that
when both are present 8” acts as a dom-
inant, and that the frequency of the
B° allele associated with that locus is
sufficiently low to be ignored. By
using this formula and following the
genetic scheme proposed by Birney and
Perez (1971), estimates of the frequency
of all other alleles for both species can
be calculated as accurately as size of
available samples permits (Table 20).
Changes in hemoglobin allele fre-
quency of Mus musculus on the Jutland
Peninsula appeared to Selander, Hunt,
and Yang (1969:384) to be directional
from west to east, but in the United
States variation apparently is north to
south (Selander, Yang, and Hunt, 1969:
285). The frequency of the £1’ allele in
N. micropus fluctuates geographically,
but no clear picture of the nature of this
variation emerges from examination of
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 147
the three populations (Table 20) which
have sufficiently large samples to warrant
calculation of gene frequencies. Some
individuals at all localities sampled pos-
sess the allele and it probably is wide-
spread in the population. However, it
was not found to be fixed at any locality.
The 8? locus is polymorphic at the four
western localities sampled, but the 7
allele may be fixed in eastern populations
of the species as indicated by the absence
of phenotype A in samples from Meade
and Barber counties and in the “hybrid”
sample from Oklahoma. The £7 locus
was polymorphic in N. floridana at only
one locality (Finney County, Kansas),
but additional sampling might have
yielded animals of phenotype F from
other localities.
Two populations of N. floridana
(campestris from Russell County and
baileyi) appear to have slightly higher
frequencies of the £' allele and consider-
ably higher frequencies of the f° allele
than do other populations of the species
(Table 20). Of the 17 woodrats from
Russell County, 16 were from a single
juniper windbreak and all of these had
the £° allele; hemoglobin of the only
animal obtained from another windbreak
several miles distant lacked band 3.
None of the 13 individuals of N. f.
attwateri from Douglas County lacked
band 1, but hemoglobin of one of four
animals from Ellsworth County (near
the attwateri-campestris subspecies boun-
dary ) did not form the band (Table 19).
Frequency of 8° appears to be low in the
sampled populations of N. f. attwateri,
but the relatively high frequency of this
allele in the “hybrid” population from
Major County, Oklahoma, indicates that
in adjacent populations of N. f. attwateri
the frequency of this allele is either rela-
tively high or that phenotype G conveys
a strong selective advantage.
Presence of hemoglobin phenotype G
in several individuals from 3 mi S Ches-
ter, Major Co., Oklahoma, clearly indi-
cates that the two species have hybrid-
ized at this locality. The phenotype has
been observed previously in known hy-
brids (Birney and Perez, 1971), but not
in woodrats of either species from local-
ities of allopatry.
Functional relationships of the dif-
TABLE 20. Frequency of hemoglobin alleles at selected localities of Neotoma floridana and
N. micropus. Localities with samples of less than 10 individuals are not shown separately but
are included in totals.
Sample N Bl’ Bl Bo? [spas faio) Bom 60D
Neotoma floridana baileyi
Cherry County, Nebraska ILy/ 0.00 0.36 0.64 1.00 0.00 0.76 0.24
All localities 19 0.00 0.35 0.65 1.00 0.00 Ont O23
Neotoma floridana campestris
Russell County, Kansas 17, 0.00 0.23 0.77 1.00 0.00 0.76 0.24
All localities 35 0.00 0.44 0.56 0.76 0.24 0.37 0.63
Neotoma floridana attwateri
Douglas County, Kansas 13 0.00 1.00 0.00 1.00 0.00 0.12 0.88
All localities 17 0.00 0.76 0.24 1.00 0.00 0.13 0.87
Neotoma floridana
All localities 71 0.00 0.47 0.53 0:63 ‘O”'7 0.35 0.65
Neotoma micropus canescens
Baca County, Colorado 29 0.44 0.56 0.00 0.68 0.32
Haskell and Stevens counties, Kansas 22 0.23 .0:77% 0:00 0.57 0.43
Barber County, Kansas 13 0.32 0.68 0.00 1.00 0.00
All localities 74 0.33 0.67 0.00 O67, 0:33
Neotoma sp.
Major County, Oklahoma 13 iS 1.00 0.00 0.32 0.68
“See text for assumptions made to calculate frequencies of these alleles for N. micropus.
> There presently is no evidence that this locus occurs in N. micropus.
° Frequency of these alleles in this population cannot be calculated.
148 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
ferent hemoglobin phenotypes are un-
known. The data appear to indicate a
poorly defined tendency for animals from
arid habitats to have fewer electropho-
retic bands (thus fewer kinds of beta
polypeptides) than animals from more
mesic habitats. Manwell et al. (1963)
found that hemoglobins of hybrids may
have selective advantages over those of
either parental species in some birds,
but no data are available on this subject
for woodrats.
Immunoelectrophoresis of Esterases
It has been shown that injections of
whole serum alone stimulate production
of a relatively specific antiserum of low
antibody titer (Durand and Schneider,
1963), but that whole serum emulsified
with complete Freund’s adjuvant results
in an antiserum of relatively high anti-
body titer and low specificity (Anthony,
1965). Because adjuvant was used in
this study, antisera were of the latter
type. A pilot study of precipitin tests
(Boyden, 1964, and elsewhere ) indicated
that either the antisera were not suf-
ficiently specific to distinguish minor dif-
ferences in woodrat proteins, or that pro-
teins of the closely related woodrats un-
der study had not diverged perceptibly
at the sites of antigen-antibody reaction.
Anthony (1965) found that precipitin
tests were inefficient for comparing
closely related races and species of the
genus Canis.
Micro-immunoelectrophoresis (Schnei-
degger, 1955) has a distinct advantage
over precipitin testing because individual
arcs of precipitate are formed. However,
Gerber (1968) observed that neither to-
tal counts nor weighted scores based on
intensity of general protein arcs were
reliably indicative of systematic relation-
ships of bats. To reduce the number of
arcs to be considered, Anthony (1965)
conducted immunoelectrophoresis and
differentially stained only for esterases.
Because intra- and interspecific varia-
tion in esterases is well known (see Au-
gustinsson, 1961) and because it was
desirable to determine if the immune
reaction might further elucidate informa-
tion on the relationships of woodrats, this
technique was employed.
Materials and Methods.—Rats were
bled by cardiac puncture. Sera were sep-
arated by centrifugation and preserved
by freezing at -15°C. Antisera against
pooled samples of whole sera were pre-
pared in rabbits following the procedure
outlined by Gerber and Birney (1968:
413). Antisera obtained following the
second series of immunizing injections
were used in all reactions. Woodrats
from which sera were used for produc-
tion of antiserum are as follows: Neo-
toma floridana baileyi—15, from Cherry
County, Nebraska (A); N. f. campestris
—S&, from Logan and Finney counties,
Kansas (B); N. f. attwateri—l4, from
Douglas County, Kansas (F); N. f.
magister—4, from Giles County, Virginia
(G); N. m. canescens—16, from Haskell
County, Kansas (1); N. m. canescens—
13, from Barber County, Kansas (K).
Serum of each of the above-listed wood-
rats also was used in reactions with anti-
sera and, in addition, sera of woodrats
listed below were reacted against anti-
sera but not used in production of the
latter: N. f. campestris—l4, from Ellis
County, Kansas (C); N. f. campestris—
4, from Russell County, Kansas (D); N.
f. attwateri—1, from Ellsworth County,
Kansas (E); N. m. canescens—11, from
Baca County, Colorado (H); N. m.
canescens—7, from Meade County, Kan-
sas (J); Neotoma sp.—3, from area of
sympatry in Major County, Oklahoma
(L). Letters following localities indicate
geographic origin of specimens in figure
42 and table 21. All animals used were
adults and had been in captivity at least
two weeks. An attempt was made to in-
clude an equal number of animals of
both sexes in each sample, but smaller
samples did not always have equal sex
ratios.
The sample of Neotoma_ floridana
magister was included to serve as a
standard for other comparisons and be-
cause the taxonomic status of this taxon
is unclear; magister may be a species dis-
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 149
tinct from other populations of floridana.
Concentration of protein-nitrogen for
immunoelectrophoresis and for injecting
rabbits was determined with an Aloe-
Hitachi hand protein-refractometer. Se-
rum was diluted to contain one gram per
cent protein. Slides for immunoelectro-
phoresis were prepared by layering three
ml of a two percent Ionager solution on
each microscope slide. The arrangement
of antigen wells and antibody troughs
used is shown in figure 40. Electropho-
resis was conducted in Michalis’ buffer,
ionic strength 0.05, pH 8.7, for 35 min-
utes at 40 volts. Ten lambda of unpooled
serum from individual woodrats were
placed in each antigen well immediately
prior to electrophoresis. Each slide was
prepared in duplicate. Following elec-
trophoresis, gel in the precut trough was
removed and the trough filled with anti-
serum. Reactants were allowed to inter-
act in a humidity chamber for 24 hours.
Unbound protein was removed by wash-
ing the agar slides for two days in three
washes of borate-buffered saline, pH 8.6.
Salts were removed similarly in three
rinses of distilled water. The agar then
was dried to a thin film and stained for
esterase activity. The staining solution
consisted of 40 ml of 0.2 M Tris-maleate
and 0.2 M sodium hydroxide adjusted to
a pH of 7.0, 1 ml of one per cent «-
naphthyl acetate (in acetone), and 20
mg of Fast Blue RR diazonium salt.
Reagents were mixed immediately be-
fore use and gels incubated in the solu-
tion for 20 minutes at room temperature.
Stained slides were soaked for 15 min-
utes in a two per cent glycerol solution
to prevent cracking and peeling of the
agar.
The size and intensity of the major
esterase band (Fig. 41) formed by the
antigen of each woodrat against each
antiserum was assigned a value on a
scale of zero to eight. The minor band
was scored similarly on a zero to two
scale. Exemplary slides were selected
with bands of each value to standardize
scoring. The two values for each indi-
vidual were added together and sub-
Antigen well
Antibody trough
ee)
O
Anode
a
no)
°
<=
~
©
oO
Fic. 40. Diagrammatic representation of
microscope slide with Ionagar gel as used for
immunoelectrophoresis.
jected to a Y + 1 conversion to eliminate
zero scores. These values then were
averaged for the woodrats from each lo-
cality. Because six antisera were used
and two bands were considered for each
antiserum, a total of 12 values was calcu-
lated for specimens from each locality.
These values were used as characters and
the sample from each locality was treated
as an OTU in the CLSNT subroutine dis-
cussed previously.
Results and Discussion —Mean values
of scores for size and intensity of esterase
bands are shown in table 21. It is im-
mediately apparent that band scores for
the population of N. f. campestris from
Ellis County are highest in every case.
Normally, in immunological tests, the
homologous reaction is expected to ex-
ceed all cross reactions, and cross reac-
tions are considered in terms of percent
immunological correspondence to the
homologous reaction, which is set at 100.
This technique is clearly not applicable
in evaluation of the data at hand; even
when the population from Ellis County
is disregarded, the homologous reaction
invariably is exceeded by at least one
other cross reaction.
Anthony (1965) found that the im-
munological response to esterase antigens
in cross reactions often surpassed that in
reference reactions in studies of dogs.
Several variables apparently interact to
result in this phenomenon. The number
of evolutionarily based changes in ester-
ase molecules at antibody-antigen reac-
tion sites between closely related popula-
tions undoubtedly is low, antiserum pro-
duced against an emulsion of whole
serum and adjuvant is not highly specific,
individual subjects have varying concen-
150 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
Fic. 41. Examples of esterase bands formed
by differentially staining antigen-antibody pre-
cipitate in dried Ionagar on microscope slides.
The antiserum used was prepared against the
serum of Neotoma floridana campestris. Sepa-
rate samples of serum from two woodrats were
placed in the wells (left and right) of each
slide as follows: A—N. f. campestris from lo-
cality C; B—N. f. baileyi from locality A; C—
N. f. attwateri from locality F; D—N. f. magis-
ter from locality G; E—N. micropus canescens
from locality I; F—N. m. canescens from lo-
cality K. See accompanying text for explanation
of locality codes.
trations of an enzyme in the serum de-
pending on a variety of both intrinsic
and extrinsic factors (see, for example,
Jones and Bunde, 1970), and the cataly-
tic action of enzymes is often reduced by
reaction with corresponding antibodies,
especially in antibody excess (Cinader,
1957:373). If the antigen of a given sam-
ple contained a sufficient quantity of
esterase molecules to stimulate produc-
tion of a high titer of anti-esterase anti-
bodies of relatively low specificity, and
if a related sample contained the same
or a similar esterase in greater quantity,
the cross reaction would be expected to
exceed the reference reaction when the
two samples were tested. Therefore, the
immune reaction involving single en-
zymes has severe limitations when com-
paring closely related taxa.
Nevertheless, Anthony (1965) found
that correlations of these kinds of data
frequently corresponded well with gen-
erally accepted theories of relationships
of various breeds of dogs. The correla-
tion and distance phenograms as calcu-
lated by CLSNT for the woodrats studied
are shown in figure 42. Values for N. f.
campestris (C) from Ellis County are
sufficiently greater than values for other
samples that the distance phenogram
separates that sample from all others at
a distance (2.36) nearly double that
(1.24) of the next major separation.
Elsewhere in the distance phenogram,
the two samples of N. f. attwateri appear
as a subgroup closely allied to the hybrid
sample from Oklahoma, the three sam-
ples of N. m. canescens from adjacent lo-
calities in Kansas form a single subgroup,
but samples from the remaining localities
do not correspond well with other data
concerning relationships.
In the correlation phenogram, which
should reflect the relative degree of re-
activity (enzyme similarity?) rather than
the magnitude of reactions, the Ellis
County population is closely coupled
with the sample of N. f. attwateri from
nearby Ellsworth County. The sample
of N. f. attwateri from Douglas County
is next to join that subgroup, followed
by the sample from the locality of sym-
patry. It was expected that the popula-
tion of N. f. campestris (D) from Russell
County, which is geographically and
morphologically intermediate between
those from Ellis and Ellsworth counties,
would also be in that subgroup. How-
ever, that sample formed a relatively
distinct subgroup with the sample of N.
f. magister, to which it certainly is not
closely allied either geographically or
morphologically.
The sample of N. f. baileyi, and to
a lesser extent, the sample of N. f. cam-
pestris (B) from Logan and Finney
counties, Kansas, appear in both pheno-
grams to have esterases more like those
of N. micropus than like those of other
populations of N. floridana. This rela-
tionship may somehow correspond more
151
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA
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MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
N.f. baileyi A
N.m. canescens H
A
N. m. canescens I
N.f. campestris B
N.m. canescens K
N.m. canescens J
N.f. campestris D
N.f. magister G
N.f. campestris (e
N.f. attwateri E
N.f. attwateri F
Neotoma sp. L
N.f. baileyi A
N.f.campestris B
B
N.m. canescens H
N. m. canescens K
N.m. canescens ]
N.m. canescens J
N.f. campestris D
N.f.magister G
N.f. attwateri E
N.f. attwateri F
Neotoma sp. L
N.f. campestris C
a gg sp “gs
2.36 1.96 1.56 1.16 0.76 0.36
Fic. 42. Correlation (A) and distance (B) phenograms generated from
mean scores of size and intensity of precipitated esterase-antibody bands. The
coefficient of cophentic correlation of A is 0.792, whereas that of B is 0.895.
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 153
to adaptation to arid, relatively harsh en-
vironments than to phylogeny. For
whatever reason, both phenograms also
indicate that, with respect to esterases,
the sample of suspected hybrids from
Major County, Oklahoma, more closely
resembles floridana from eastern Kansas
than it does western populations of mi-
cropus. This result is not consistent with
characteristics of pelage and skulls of the
specimens involved.
The fact that rather well marked dif-
ferences in the antibody-antigen esterase
bands were observed between woodrats
of the two species from different locali-
ties clearly shows that esterases in wood-
rats differ qualitatively, quantitatively,
or both. However, these data must be
interpreted with respect to all other data
relating to the supposed relationships of
the various populations studied. Addi-
tional studies on individual variation of
esterases, quantitative variation of the
esterases of an individual under various
environmental conditions, and antibody
specificity to enzymes will be necessary
before data such as these can be fully
and reliably interpreted with respect to
the relationships of mammals.
COMPARATIVE KARYOLOGY
The karyotype of Neotoma floridana
first was described by Cross (1931), who
reported the diploid number as 52. Mat-
they (1953) verified the diploid number
and described two large submetacentric
and two large subtelocentric chromo-
somes in the complement. Mitotic chro-
mosomes of Neotoma micropus were
described by Hsu and_ Benirschke
(1968); the diploid number was shown
to be 52 and the karotype illustrated re-
sembled that reported for floridana.
Baker and Mascarello (1960) de-
scribed the chromosomes of several spe-
cies of Neotoma, and redescribed the
karyotypes of both floridana and micro-
pus. They reported that the number of
large biarmed elements varies from one
to four in micropus, but that females of
floridana have four biarms and males
have three. They concluded that the Y
is a medium-sized subtelocentric chro-
mosome in both species. The chromo-
somal polymorphism in micropus was
discussed by Baker et al. (1970) and
shown to be a widespread phenomenon
geographically, involving the X chromo-
somes and one pair of large autosomes.
Materials and Methods.—Prepara-
tions of chromosomes were made from
cells in bone marrow using a modifica-
tion of the blaze-dry techniques de-
scribed by Patton (1967) and Lee
(1969). Chromosomes were stained in
a saturated solution of crystal violet.
Only specimens collected from natural
populations are reported. Results dis-
cussed below are based on study of at
least 10 chromosome spreads from each
of 58 woodrats, including specimens of
Neotoma floridana baileyi, N. f. campes-
tris, N. f. attwateri, and Neotoma micro-
pus canescens. Included also are six
specimens collected from the area of
sympatry between floridana and micro-
pus—3 mi S Chester, Major Co., Okla-
homa.
The maximum number of chromo-
somes counted in any cell was 52. Some
cells had less than 52 chromosomes, but
the difference undoubtedly resulted from
a loss of chromosomes during prepara-
tion. Those having less than 52 chromo-
somes were not studied or included in
the 10 counts. In complete cells, no in-
traindividual variation beyond that at-
tributable to differential contraction of
chromosomes was observed.
Results and Discussion.—A consistent
but relatively subtle (and heretofore un-
noted) difference exists between the
karyotypes of Neotoma floridana and
Neotoma micropus, irrespective of the
number of large biarmed elements. In
the karyotype of both there is a graded
series of 22 pairs of so-called acrocentrics.
However, only rarely can chromatin be
seen beyond the centromere opposite the
arm in metaphase preparations of the
acrocentric chromosomes of micropus,
whereas in floridana there is invariably a
visable amount of chromatin beyond the
154 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
centromeres of at least the larger acro-
centrics. These tiny “arms” are evident
in the karyotype of an N. f. attwateri
illustrated by Baker and Mascarello
(1969:189) and also were present in the
karyotypes of floridana studied by me.
If considered to be chromosome arms,
these bits of chromatin would increase
the Fundamental Number (FN) of the
karyotype of N. floridana. Only in re-
laxed spreads of N. f. campestris, how-
ever, are these “arms” sufficiently large
to cause difficulty in determining the
number of biarmed chromosomes. Until
more information concerning — these
“arms is available, I consider it best not
to include them in calculations of the
FN and have attempted to distinguish
such chromosomes from the subtelocen-
trics that are involved in the polymorphic
system. Although it may be misleading
to refer to these chromosomes as acro-
centrics, I will do so in an attempt to
preserve the terminology used by Baker
and Mascarello (1969).
In the chromosomal complement of
each of the nine female N. f. baileyi ex-
amined, only two large and distinctly
biarmed elements were seen (Fig. 43);
in each instance the two biarms were of
nearly equal size. Two distinctly bi-
armed elements (one noticeably larger
than the other) also were seen among the
chromosomes of each of the four male
baileyi karyotyped (Fig. 43). There is
no chromosome in baileyi males that
closely resembles the chromosome Baker
and Mascarello (1969:189) designated as
the Y of N. f. attwateri. Therefore, I
consider the smaller of these two sub-
metacentric elements as the Y chromo-
some and the larger as the X. In three
male N. f. attwateri from Douglas
County, Kansas, four biarmed elements
were observed (Fig. 44). Three had
arms of unequal length and were dis-
tinctly larger than the fourth in each in-
stance. The fourth was indistinguishable
from the chromosome thought to be the
Y in baileyi. Each of six N. f. attwateri
females (two from Ellsworth County and
four from Douglas County, Kansas) had
four, large, biarmed chromosomes that
were indistinguishable from the three
larger biarms described for males. The
karyotype of these females was like that
described by Baker and Mascarello (loc.
cit.) for five females from Payne County,
Oklahoma. Apparently the Y chromo-
some varies in attwateri, but because I
examined only three males from a single
locality, and Baker and = Mascarello
studied only two from another locality,
it is not possible to determine if the vari-
ation is geographic or if it is polymorphic
at some localities. Available evidence in-
dicates that the number of large biarmed
chromosomes exclusive of the Y is con-
stant in attwateri at four in females and
three in males.
A small submetacentric chromosome
that is indistinguishable from the Y in
baileyi and in attwateri from Douglas
County was seen in the karyotypes of
three of four N. f. campestris males. These
animals were from Logan, Finney, and
Russell counties, Kansas. The fourth male,
from Ness County, Kansas (Fig. 44),
lacked such a chromosome, but several
“acrocentrics” in the preparation had suf-
ficiently large “arms” beyond the centro-
mere as to be considered subtelocentrics;
one of these probably is the Y. Addition-
ally in the Ness County male, there is
one large submetacentric, one large sub-
telocentric, and another large chromo-
some that may be a subtelocentric. In
the karyotype of each of the other three
animals there is one large submetacen-
tric chromosome, one distinctly subtelo-
centric element, and a third large chro-
mosome that probably is a subtelocentric
but may be an “acrocentric.” The karyo-
types of nine female campestris all were
characterized by two large submetacen-
trics and either one or two large subtelo-
centrics. One female from Finney
County had two subtelocentrics in all
except one of the cells examined; chro-
mosomes in this cell were severely con-
tracted and the two subtelocentrics were
indistinguishable from acrocentrics of
similar size. The presence of two large
submetacentrics in females and one in
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 155
ax 2am & Jo Vv i
an 02 pf AN 6K Ak 46 tA
TY a ee, er, oe | ee
aw 6 aa aan ae ~~ ae
B2
aa af (8) nae
LANA NGQ RRKHA RZ ANAM
nh AR ALR AB Ar ON AH AA
~a— NA AR AR Ae ee MR
Fic. 43. Karyotypes of a female (A) and a
male (B) Neotoma floridana baileyi from Rock
and Cherry counties, Nebraska, respectively.
The scale applies to both karyotypes.
males indicates that these are the X
chromosomes. The presence of one sub-
telocentric in some females and two in
others may represent a polymorphic sys-
tem the same as, or similar to, that dis-
cussed by Baker et al. (1970) for N.
micropus. On the other hand, these
observations may be a result of the dif-
ficulty in distinguishing large subtelo-
centrics from the so-called acrocentrics.
A medium-sized subtelocentric chro-
mosome was present in each of the
karyotypes of five N. m. canescens males
(three from Barber County and two from
Haskell County, Kansas). This element
was not seen in any of the karyotypes of
11 females and undoubtedly is the Y
chromosome as shown by Baker and
Mascarello (1969) and by Baker et al.
(1970). Both males from Haskell County
had one large submetacentric and one
large subtelocentric in addition to the
Y chromosome. The three males from
Barber County each had one large sub-
metacentric and two large subtelocen-
trics.
Three of four female N. m. canescens
from Baca County, Colorado, one of two
from Haskell County, Kansas, and four
XY
ah 62 fh fe 0b fe tt oe
Fae Wee ee) |
PY eeeey Qe ana Om 6
Pe ee “y
oa Gf Mh ft Ak te he te
ai eo nb oa 46 86 08 4a
PY ee Y ee Y ee
Fic. 44. Karyotypes of a male Neotoma
floridana attwateri (A) from Douglas County,
Kansas, and a male N. f. campestris (B) from
Ness County, Kansas. The scale applies to both
karyotypes.
of five from Barber County, Kansas, each
had two large submetacentrics and two
large subtelocentrics. The karyotypes of
these animals were indistinguishable
from that illustrated by Hsu _ and
Benirschke (1968) for a micropus fe-
male. The other three females each had
two large submetacentrics, but only a
single subtelocentric.
Two males, both identified as hy-
brids, from the area of sympatry between
floridana and micropus (3 mi S Chester,
Major Co., Oklahoma) had karyotypes
indistinguishable from those of the three
male N. micropus from Barber County,
Kansas. Four females identified as mi-
cropus from that locality each had four
large biarmed elements. The karyotypes
of three of these were indistinguishable
from that of micropus females having
four biarms, but the fourth had two acro-
centrics with tiny “arms” as described
for floridana. The presence of floridana-
156 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
like acrocentrics in the karyotype of this
animal undoubtedly resulted from hy-
bridization of the two species. A female
identified as a hybrid had three distinctly
biarmed elements, but spreads were not
sufficient to determine the presence or
absence of “arms” beyond the centro-
mere of large acrocentrics.
The polymorphic system involving
the number of large biarmed chromo-
somes in N. micropus reported by Baker
and Mascarello (1968) and discussed by
Baker et al. (1970) probably will be
found to exist throughout the range of
the species. Baker et al. discussed vari-
ation in number of biarms in animals
from three widely separated localities in
Texas and one locality in Oklahoma. The
karyotype is now known to be variable
at one locality in Colorado and two in
Kansas. The only locality from which
specimens of micropus have been karyo-
typed and not reported to be polymor-
phic is 16 km N Ciudad Victoria, Tamau-
lipas (Hsu and Benirschke, 1968). These
animals were of the subspecies N. m. mi-
cropus, whereas the polymorphic popula-
tions all are N. m. canescens. However,
Hsu and Benirschke (1968) did not indi-
cate if chromosomes of more than two
rats (the karyotypes illustrated) from
Tamaulipas were examined. Baker et al.
(1970) discussed the possible origin of
polymorphism in micropus; apparently it
is the result of neither a Robertsonian
change (as frequently is seen in mam-
mals) nor of a single pericentric inver-
sion. These authors suggested that both
inversions and translocations may be in-
volved in the origin of this system.
The discovery of a submetacentric Y
chromosome in some populations of N.
floridana is of interest. No other species
of the genus has been reported to have
a submetacentric Y chromosome and,
although the karyotype of N. f. baileyi
was not found to vary, these findings in-
dicate that a previously undescribed
polymorphism exists in the Y chromo-
some of N. f. attwateri and N. f. campes-
tris. The number of large biarmed chro-
mosomes (exclusive of the Y) has not
been found to vary from three in males
and four in females for N. f. attwateri,
but only two biarms were seen in the
karyotype of the nine baileyi females and
only one (exclusive of the Y) in the four
baileyi males examined. In N. f. campes-
tris, the number of large submetacentric
chromosomes seems to be constant at two
in females and one in males. Although
it is difficult to distinguish large subtelo-
centrics from some “acrocentrics” in rats
of this subspecies, apparently the num-
ber fluctuates from zero to two. The
large biarms in baileyi and the large sub-
metacentrics in campestris probably are
the X chromosomes, but in attwateri the
X chromosomes cannot be certainly
identified.
As shown by Baker et al. (1970), the
X chromosomes in micropus cannot be
distinguished with certainty, because
polymorphism is involved and also be-
cause the relative lengths of the arms in
the large, biarmed chromosomes is vari-
able. In the micropus examined by me,
at least one large submetacentric always
was found in males and two such ele-
ments were present in females; in the
absence of other information these would
appear to be the X chromosomes. How-
ever, Baker et al. (1970) reported two
females that had only one large, biarmed
chromosome. All males examined by
them had at least one biarmed chromo-
some in addition to the smaller subtelo-
centric Y. This chromosome probably is
the X, but as seen in the two females
having only a single biarmed element,
at least one X can be an acrocentric in
females.
Because of the limited number of
animals examined and the chromo-
somal complexity of this group, a discus-
sion of the evolution of chromosomes in
N. floridana and N. micropys is some-
what premature. However, in N. flori-
dana previously reported by Cross
(1931), Matthey (1953), and Baker and
Mascarello (1969), and in N. f. attwateri
from northeastern Kansas, the number
of biarmed chromosomes was always
four in females and three plus the Y in
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 157
males. This is also the number of biarms
reported for N. m. micropus from
Tamaulipas and the most common karyo-
type seen in N. m. canescens. It is likely,
then, that this is the karyotype from
which others have evolved. The number
of large biarms is unstable in micropus
and possibly fluctuates in N. f. campes-
tris, but in N. f. baileyi the two biarmed
autosomes have been replaced by two
acrocentrics.
Because the Y chromosome is a me-
dium-sized subtelocentric in all popula-
tions of N. micropus examined and in all
floridana that have been examined ex-
cepting baileyi, some campestris, and the
attwateri from northeastern Kansas, the
subtelocentric undoubtedly is the primi-
tive Y chromosome and the submetacen-
tric is derived. If it is eventually found
that the lengthened arm of the submeta-
centric Y was acquired by a transloca-
tion of an arm of one of the original
biarmed autosomes, then the two poly-
morphic systems may have a common
origin. In any event, the submetacentric
Y chromosome evidently was present in
at least some floridana males prior to the
time baileyi and campestris dispersed to
the geographic areas they now occupy.
The apparent fixation of this element in
baileyi is not surprising considering that
the subspecies is isolated in a relatively
small geographic area. The submetacen-
tric Y probably is commoner than the
subtelocentric in campestris. Both forms
of the Y chromosome are known in at-
twateri; but the relative status of the
two is not known.
SUMMARY AND ZOOGEOGRAPHIC CONSIDERATIONS
Neotoma angustipalata, N. floridana,
and N. micropus form a closely related
complex of almost entirely allopatric
taxa. The distributions of floridana and
micropus are most appropriately termed
stasipatric. Key (1968:22) discussed
stasipatry as follows: “We could perhaps
distinguish a condition of ‘stasipatry’ as
a special case of parapatry in which the
zone of overlap is limited by an impair-
ment of the fecundity of freely produced
hybrids rather than by ecological fac-
tors... The only known locality where
the two species occur together (3 mi S
Chester, Major Co., Oklahoma) is char-
acterized by the presence of hybrids,
identification of which was based on a
variety of comparisons with hybrids
reared in the laboratory. For example,
the electrophoretic pattern of hemoglo-
bins of some animals from the locality
of sympatry was otherwise observed only
in known hybrids; discriminant function
analysis based on 17 characters of speci-
mens of the two groups indicated they
were generally intermediate between
non-hybrid specimens of the two species;
and the karyotype of one animal from the
locality in question almost certainly con-
tained chromosomes derived from both
species.
There is no reason to believe that
floridana and micropus ever have oc-
curred together without producing na-
tural hybrids or that they will do so in
the near future. Although floridana gen-
erally is an inhabitant of relatively mesic
woodland habitats (N. f. campestris be-
ing a notable exception) and micropus
generally is associated with arid grass-
lands, either species probably could ex-
pand its range (at least slightly) in the
absence of the other (although the exis-
tence of a relatively broad hiatus be-
tween the distributions of the two species
throughout much of the region of poten-
tial contact might argue against the latter
point). In any event, the two apparently
hybridize when in contact and results of
laboratory breeding studies strongly sug-
gest some hybrid inviability. By defini-
tion, then, “stasipatry” best explains the
distributional relationship of these two
woodrats.
The distribution of N. floridana is
not contiguous with that of N. angusti-
palata. Neotoma micropus and N. an-
gustipalata occupy adjacent geographic
158 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
areas, but sympatry is unknown and no
evidence of natural hybridization has
been uncovered (but, see Alvarez, 1963:
452). To predict how micropus and
angustipalata would act if they were
sympatric clearly is speculative; repre-
sentatives of angustipalata are larger
than are those of micropus from adjacent
localities in México and I doubt that the
two would hybridize. However, size
alone apparently is a relatively inefficient
isolating mechanism among woodrats.
Morphologically, angustipalata is approx-
imately as distinct from both floridana
and micropus as these two species are
from each other.
Considering the fact that floridana
and micropus hybridize in the laboratory
and also in nature, some systematists
might argue that the two are conspecific.
However, micropus and floridana have
maintained a high level of specific in-
tegrity in the past, apparently are doing
so at present, and I predict, after exten-
sive field and laboratory study, that they
will continue to do so. Although there
obviously is at least some genetic com-
patibility between floridana and micro-
pus, the process of speciation between
the two is essentially complete, and I
regard it as having reached an irrever-
sible point in time. Furthermore, I do
not believe that our understanding of
the evolutionary history and systematic
relationship of these rats would be en-
hanced by formally placing micropus in
the specific synonymy of floridana. In
fact, such an arrangement would suggest
that the two intergrade broadly and are
more closely related than is the case. If
considered as a single species, individuals
or populations that should be studied
separately might eventually be treated
together in research by non-taxonom-
ically oriented biologists, whose research
design is partially dependent on deci-
sions by taxonomists.
Despite my convictions that floridana
and micropus should be considered sepa-
rate species, certain data indicate that
hybridization is, or recently has been,
introgressive. Analyses of frequency and
size of the fork on the anterior palatal
spine and of the morphology of the pos-
terior margin of the bony palate indicate
that in some instances one or more pop-
ulations of one species from localities
geographically contiguous with popula-
tions of the other may have acquired
selected genetic material introgressively.
This was suggested most strongly by pop-
ulations of floridana in Oklahoma and
Texas. Also, specimens of micropus from
localities adjacent to the range of flori-
dana in south-central Kansas and coastal
Texas are larger (thus somewhat like
floridana) than specimens of micropus
from localities not geographically contig-
uous with populations of floridana. It is
possible that each species is selectively
acquiring a limited amount of genetic
material from the other (Key, 1968;
Lewontin and Birch, 1966). However,
certain other characters, such as electro-
phoretic patterns of hemoglobins and
analyses of karyotypes, do not indicate
introgression. Introgression is extremely
difficult to “prove” or “disprove,” and in
the case of floridana and micropus
elucidation of this phenomenon must
await additional data.
The micropus species-group estab-
lished by Burt and Barkalow (1942) is
meaningless. The three species studied
(angustipalata, floridana, and micropus )
share a common ancestor in the not too
distant past and represent a single spe-
cies-group, the floridana-group. Ander-
son (1969) and Finley (1958) have
shown that N. albigula is closely allied
to N. micropus (Burt, 1960; Hooper,
1960), and Anderson (1969) indicated
the possibility that floridana, micropus,
and albigula eventually may best be con-
sidered a single species. Thus, it would
seem that albigula and related species
(palatina, nelsoni, and varia—see Hall
and Genoways, 1970) also should be in-
cluded in the floridana-group.
When the nomenclatorial arrange-
ments of floridana and micropus are con-
sidered below the level of the species,
some conclusions are relatively clearcut,
whereas others are somewhat arbitrary.
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 159
Among populations of floridana studied,
total geographic variation was less than
that found in micropus. Neotoma flori-
dana baileyi has certain unique features
of the skull, and is relatively less variable
than other samples as evinced by the
absence of intraspecific variation in chro-
mosomal complement and by lower co-
efficients of variation in most mensural
characters; baileyi also has evolved a
relatively distinctive pattern of repro-
duction. In certain aspects, some cranial
dimensions and color for example, baileyi
appears to have its affinities as much
with campestris as with attwateri, but in
final multivariate analysis, baileyi ap-
peared more like attwateri than like
campestris. As discussed beyond, the
probable evolutionary history of these
woodrats also suggests that the affinities
of baileyi are with attwateri.
Neotoma floridana campestris is the
most distinctive of the western subspe-
cies of floridana with respect to color.
Statistical analysis of mensural data indi-
cated that in a few instances attwateri
is larger than campestris. Specimens in
a sample of campestris from Colorado
and Nebraska were especially small rela-
tive to those in two samples of attwateri
from localities in Kansas. A tendency
was observed for woodrats from the zone
of intergradation between campestris
and attwateri to be larger than indi-
viduals in adjacent populations of either
subspecies and for rats from localities
west of this zone to become clinally
smaller. Apparently, campestris exists in
relatively small and semi-isolated popu-
lations that occupy discontinuous areas
of suitable habitat. One acquires this
impression in field study of campestris
and additional evidence of localized
stocks includes: 1) high variability of
mensural characters in samples of this
subspecies; 2) two of six animals from a
semi-isolated population in Finney
County, Kansas, had unique hemoglobin;
and 3) three males each from different
populations had a submetacentric Y chro-
mosome, but a male from a fourth pop-
ulation had a subtelocentric Y chromo-
some.
Neotoma floridana attwateri, as here
recognized, includes those animals pre-
viously assigned to attwateri and to the
subspecies osagensis. As indicated above,
specimens assignable to attwateri from
near the range of campestris are espe-
cially large. Those from southeastern
Kansas and southern Texas were next
largest among the samples studied, and
those from eastern Oklahoma and north-
eastern Kansas were smallest. The sub-
species has not been found to be poly-
morphic for the number of large biarmed
chromosomes, but it is polymorphic in
the morphology of the Y chromosome.
Three males from northeastern Kansas
had a distinct submetacentric Y element,
whereas two from near Stillwater, Okla-
homa (Baker and Mascarello, 1969), had
the more common subtelocentric Y.
Variation in Neotoma micropus is
more easily definable geographically
than that in N. floridana, but more dif-
ficult to resolve nomenclatorially at the
subspecific level. N. m. planiceps is
known only by the holotype; thus varia-
tion within the subspecies is unknown.
The holotype is a small woodrat similar
in size to other Mexican representatives
of the species. Multivariate analyses
indicated that planiceps is relatively dis-
tinct morphologically from both canes-
cens and micropus. Possibly N. m. plani-
ceps and N. angustipalata represent a
single taxon. The holotype of the former
is a young adult and conclusions regard-
ing the affinities of planiceps must be
regarded as tentative.
The name N. m. micropus has been
restricted to the brownish, long-tailed
woodrats that occur on the coastal plain
and Sierra de Tamaulipas in the state of
Tamaulipas. An appreciable amount of
geographic variation exists even within
this restricted area. Woodrats become
progressively less brownish and more
grayish from south to north in Tamauli-
pas. Variation in size especially and that
in color to a lesser extent forms a sharp
step-cline across the lower Rio Grande.
160 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
However, the zone of contact between
micropus and canescens in western
Tamaulipas and eastern Nuevo Leon is
relatively broad; the type locality of N.
m. micropus (Charco Escondido, Tamau-
lipas) is in this zone of intergradation,
but woodrats from that locality resemble
more closely those from coastal Tamauli-
pas than rats from most of the range of
N. m. canescens.
Neotoma micropus canescens is the
most variable subspecies studied. Speci-
mens from northern and eastern parts of
the range are larger than those from
southern and western localities, with the
exception that specimens from coastal
southern Texas are among the largest of
the species. The darkest individuals oc-
cur in the northeastern parts of the range,
but members of the subspecies become
progressively paler from east to west.
Distributional records of available spec-
imens indicate that a large area in cen-
tral Texas is not inhabited by N. micro-
pus. If true, populations of large wood-
rats from coastal southern Texas are only
circuitously connected geographically
with populations of large woodrats to
the north. Routes of gene flow between
northern and southern populations of
large woodrats thus would include pop-
ulations of smaller western rats. The sub-
species canescens could be subdivided
into five subspecies with some merit as
discussed previously. Another logical ar-
rangement might recognize the small
pallid woodrats of New Mexico, south-
western Texas, and adjacent México (ex-
clusive of coastal Tamaulipas) as one
subspecies (leucophea) and restrict the
name canescens to the large woodrats
from the northern and eastern parts of
the range of the subspecies as here recog-
nized. However, such an arrangement
would not account for intermediacy in
size and color of woodrats from south-
sastern Colorado, the panhandle of
Texas, and non-coastal southern Texas.
It might also result in an arrangement
whereby populations of one subspecies
are separated by populations of another.
Neotoma angustipalata is known by
too few specimens to permit a meaning-
ful analysis of intraspecific variation.
Hooper (1953) commented on the ex-
treme variability in this species and I
observed the same phenomenon. More
specimens of this enigmatic species are
needed.
SUGGESTIONS FOR ADDITIONAL
RESEARCH
Many aspects of the biology, and in
particular the systematics, of woodrats
of the floridana species-group (as here
defined) need additional study. I have
attempted throughout the preceding dis-
cussions to indicate these needs, and
summarize them here. My study and
others (Anderson, 1969; Finley, 1958)
demonstrated the importance of con-
tinued field and laboratory work on the
distributional and systematic relation-
ships of N. albigula with both N. flori-
dana and N. micropus. Especially criti-
cal geographic areas include southeastern
Colorado, New Mexico, western Texas,
the Edwards Plateau, southern Chihua-
hua, and montane areas of Coahuila.
Additional field work to study the
exact distributional relationships of flori-
dana and micropus is needed in south-
eastern Colorado, and throughout the
area of general contact in Oklahoma and
Texas. Sustained search for areas of
sympatry and continued study of the one
such area now known should result in
elucidation of the distinctiveness of the
two species and the presence or absence
of introgression. Collecting efforts in that
area of central Texas not now known to
be inhabited by either Neotoma floridana
or Neotoma micropus will elucidate the
distributional status of woodrats and po-
tential routes of gene flow in that state.
The acquisition of additional specimens
of N. m. micropus and N. m. canescens
from Tamaulipas will help to clarify the
relationships of these two taxa. Speci-
mens from southern Tamaulipas and San
Luis Potosi are needed to assess the sys-
tematic status of N. angustipalata and
N. m. planiceps and to better understand
the distributional relationship of these
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 161
woodrats with adjacent populations of
N. m. micropus and N. m. canescens.
Certain problems requiring a com-
bination of field and laboratory research
have been studied, but most still lack
definitive solutions. Birney and Perez
(1971) presented hypotheses concerning
the nature of variation and the mode of
inheritance of woodrat hemoglobin, but
these hypotheses need to be tested and
refined. The chromosomal polymorphism
in the number of large biarmed chromo-
somes first reported for N. micropus by
Baker and Mascarello (1969), discussed
by Baker et al. (1970), and observed in
N. floridana by me needs to be analyzed
more intensively from the standpoint of
evolution, geographic distribution, and
function. Baker and Mascarello (1969:
195) stated that “our results demand .. .
introduction of individuals to wild pop-
ulations different in chromosomal consti-
tutions.” I do not believe that such a
means of study is necessary or advisable
and am strongly opposed to research
that might alter natural patterns of evolu-
tionary phenomena in animals. How-
ever, studies wherein mating of captive
individuals of “different chromosomal
constitution” could be followed with
analysis of meiosis in progeny would be
enlightening. The polymorphism involv-
ing the Y chromosome in N. floridana
should be studied to discern its distribu-
tion and origin.
Boice (1969) observed behavioral
differences between N. albigula and N.
micropus and Birney and Twomey
(1970) reported evidence for physiolog-
ical divergence of N. floridana and N.
micropus. These areas of research hold
promise in their own right and in terms
of clarifying the overall systematics of
the woodrats of the floridana species-
group.
ZOOGEOGRAPHIC COMMENTS
Hibbard (1967:128) suggested that
“the stock that gave rise to Neotoma
must have separated off from a general-
ized cricetine in the Upper Miocene.”
He considered the extinct genus Plio-
tomodon, named by Hoffmeister (1945)
from Pliocene deposits in California, as
a specialized side branch related to Neo-
toma, but not in the direct lineage of
Recent woodrats. The specimen from
the Cumberland Cave Fauna ( Pleisto-
cene) named as a distinct genus, Para-
hodomys, by Gidley and Gazin (1933:
356) may represent another such off-
shoot, but also best may be considered
as a member of the genus Neotoma.
The three species of Neotoma re-
ferred to the subgenus Paraneotoma by
Hibbard (1967) from the Upper Plio-
cene and Middle Pleistocene of Kansas
are more like N. (Hodomys) alleni than
Recent members of the subgenus Neo-
toma. It is not possible to determine
whether Paraneotoma is ancestral to Re-
cent Neotoma or if the subgenus repre-
sents a once widely distributed group
of species related to N. alleni. Alvarez
(1966:9) named N. magnodonta from
the Middle or Upper Pleistocene of Méx-
ico (state of México) as a member of the
subgenus Hodomys; thus it clearly is not
in the lineage of the floridana species-
group. The only other fossil named as
a distinct species that might relate sig-
nificantly to the evolutionary history of
the floridana species-group is N. ozark-
ensis, which was described by Brown
(1909:196) from Middle to Late Pleisto-
cene (Conard Fissure) deposits of
northern Arkansas. This woodrat may
prove to be no more than a subspecies
of floridana; however, if the specimens
are from pre-Wisconsin deposits it is
likely that they predate all but the ear-
liest processes of divergence of floridana
and micropus.
These fossil records indicate that the
genus Neotoma originated in the late
Miocene or early Pliocene and evolved
during the Pliocene to the extent that
presently recognized subgenera were dis-
tinct by the beginning of the Pleistocene.
There is no evidence that woodrats of
the floridana-group inhabited the Central
Plains during the Yarmouth. Neotoma
(Paraneotoma) taylori occurred in at least
parts of the Great Plains at that time
162 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
(Hibbard, 1967; 1970). Hibbard (1963:
209) reported a specimen that he con-
sidered more like floridana than micropus
from a late Illinoian fauna in Kansas,
and Hibbard and Taylor (1960:175) re-
ported N. micropus from the Sangamon
of Kansas. These specimens were tenta-
tively identified on the basis of the shape
of the posterior triangle of the anterior
loop of Ml. Semken (1966:151) and
Dalquest et al. (1969:249) have indi-
cated, and I concur, that this is not a
diagnostic character to distinguish the
two species. Semken (loc. cit.) reported
additional material from the late Ili-
noian that compared favorably with mi-
cropus, but he elected not to assign the
material to either species.
Dalquest et al. (1969) reported N.
floridana, N. micropus, and N. albigula
from deposits considered to be 11,000 to
8000 years BP. Although I have not
examined this material, neither the mea-
surement they used for specific identifica-
tion (breadth of molar rows) nor any
other single measurement taken by me
will serve to distinguish Recent speci-
mens of the three species. Furthermore,
identification of Recent specimens of the
three based on fragmentary skulls and
lower jaws would be difficult, especially
distinguishing between floridana and mi-
cropus. Possibly albigula occurred sym-
patrically with either floridana or micro-
pus on the Edwards Plateau in the late
Pleistocene, but I question whether mi-
cropus and floridana were in sympatry
that early and I cannot conceive of all
three species having occurred there
simultaneously.
As I interpret these findings they indi-
cate that woodrats of the floridana-group
occurred on the Great Plains by late
Ilinoian. They may have diverged from
related groups as late as the Illinoian.
Neotoma albigula and related species also
could have diverged from a floridana-
like stock during the Illinoian, because
results of most studies (e.g. Sprague,
1941; Burt and Barkalow, 1942; Burt,
1960; Hooper, 1960) indicate that micro-
pus and floridana are more alike mor-
phologically than either resembles al-
bigula.
With the advance of Wisconsin ice,
the basal stock of floridana probably re-
treated southward. Neotoma albigula
might have been restricted to the Mexi-
can Plateau or to the region of southern
California, Arizona, and New Mexico (or
both), micropus to the lowlands of
coastal southern Texas and Tamaulipas,
and floridana to the southeastern United
States, possibly to peninsular Florida
(see Sherman, 1952; Blair, 1958). Guil-
day et al. (1964:158) suggested that N.
f. magister survived Wisconsin glaciation
in the southern Appalachian Mountains.
In view of the striking morphological
and ecological distinctness of magister
as compared with all other subspecies of
floridana, I agree with Guilday et al. and
further suggest that magister and flori-
dana eventually will be found to repre-
sent biological species at least as distinct
as floridana and micropus. However, the
status of magister is beyond the scope of
the present paper and the relationship
of this taxon must await detailed field
and laboratory study.
Speculation on the distribution in
Wisconsin time of Neotoma angustipa-
lata and Neotoma palatina also is of in-
terest. The affinities of angustipalata as
shown herein are clearly with micropus
and floridana, but proclivities toward
one, more than the other, are lacking.
Neotoma palatina is thought to be most
closely related to N. albigula. Neotoma
angustipalata has a relatively restricted
range in southern Tamaulipas and San
Luis Potosi, whereas palatina is restricted
to the barranca of Rio Balanos, associated
tributaries, and adjacent uplands. Be-
sides micropus and floridana, only angus-
tipalata and palatina are characterized
by the absence of a maxillovomerine
notch. Possibly this characteristic has
evolved twice, but the solid vomerine
septum of these four species may be in-
dicative of a pre-Wisconsin common an-
cestor. Neotoma palatina apparently was
sufficiently isolated from adjacent popu-
lations of albigula to effect speciation.
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 163
Neotoma angustipalata probably was iso-
lated in montane habitats of the Sierra
Madre Oriental during the Wisconsin,
whereas micropus occurred on the coastal
lowlands. Both angustipalata and _ pala-
tina represent peripherally-distributed
species that have managed to avoid ex-
tinction, but for some reason (possibly
the presence of adjacent populations of
micropus and albigula, respectively) have
been unable to significantly expand their
ranges since the recession of Wisconsin
LCE!
Recent advances in paleobiology, ge-
ology, and meteorology have improved
understanding of late Pleistocene and
Holocene climatic and vegetational pat-
terns on the Great Plains. These data
were summarized by Hoffmann and
Jones (1970) according to post-Pleisto-
cene chronology and terminology pro-
posed by Bryson et al. (1970). During
Full-glacial (to approximately 13,000
BP), floridana and micropus probably
were completely isolated in their respec-
tive refugia. Following initial isolation,
the two incipient species evolved dis-
tinctive hemoglobins from the original
double-banded phenotype. Differences
in chromosomal complements, morphol-
ogy, and color also have evolved under
differential selective pressures since that
time. Blair (1958) included floridana
and micropus in a list of mammals and
reptiles that previously were isolated into
eastern and western populations, but that
since have reestablished contact in the
forest-grassland ecotone. The barrier
that isolated micropus and_ floridana
along the Gulf Coast of the southeastern
United States may have been the Missis-
sippi Embayment, but as discussed by
Blair (1958) most species separated by
this barrier remain disjunct. During the
more equable climate of Late-glacial
(13,000 to 10,500 BP), and with north-
eastward retreat of continental ice (de-
spite minor phases of retreat and read-
vance), both isolated populations began
a northward dispersal. During the more
continental climates of the Pre-boreal
(10,500 to 9140 BP), Boreal (9140 to
8450 BP), and Atlantic (8450 to 4680
BP), micropus and floridana reached
their present limits of distribution and
floridana at least occurred somewhat
farther north and west of the present
range (see Jones, 1964). It probably
was during this time that woodrats ad-
vanced northward along the Missouri
and westward along the Niobrara rivers.
The Smoky Hill, Saline, Republican, Ar-
kansas, and possibly other rivers and
tributaries served as corridors for flori-
dana to disperse across western Kansas
into eastern Colorado and southwestern
Nebraska. Several late Pleistocene-early
Recent records of floridana from locali-
ties north of the present range are avyail-
able (e.g., Parmalee and Jacobson, 1959;
Bader and Hall, 1960; Parmalee et al.
1961). Morphologically, N. f. baileyi
somewhat resembles N. f. campestris,
especially those specimens from popula-
tions in Colorado and southwestern Ne-
braska. Possibly there was appreciable
north-south gene flow through eastern
and central Nebraska during this period.
However, I doubt that the Sand Hills
region of Nebraska ever was inhabited
by floridana and the similarities between
baileyi and campestris more likely repre-
sent convergence. When all characters
are considered, baileyi clearly is more
closely related to attwateri from north-
eastern Kansas than to campestris.
During and following Full-glacial, the
Sierra de Tamaulipas may have served
as a barrier for the small, brownish, long-
tailed woodrats that presently occur
there. When populations of micropus
subsequently dispersed northward, these
rats reestablished contact and_ inter-
graded with other populations. The re-
sult of this intergradation and_ subse-
quent selection is the coastal subspecies
to which the name N. m. micropus is re-
stricted. The evolutionary history of N.
m. planiceps cannot be understood until
the relationships and status of this
nominal subspecies are better known.
However, planiceps apparently is iso-
lated from other populations of micropus
on the Mexican Plateau at present, but
164 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
probably has not been isolated since the
Full-glacial.
The Sub-boreal (4680 to 2690 BP)
probably was the coolest post-glacial pe-
riod on the Northern Great Plains. This
period was characterized by a southward
shift in both the northern and southern
limits of the boreal forest. It probably
was during this cooler period that flori-
dana retreated slightly southward and
eastward, leaving the isolated N. f.
baileyi in the sheltered canyons of the
Niobrara River and_ associated tribu-
taries. Jones (1964) and Hoffman and
Jones (1970) suggested that baileyi be-
came isolated during a hot, dry post-
glacial period. Although that hypothesis
remains plausible, it is now thought that
the earliest period characterized by hot,
dry climate was the Scandic (1690 to
1100 BP); the degree of distinctness ex-
hibited by baileyi suggests a longer pe-
riod of isolation. Rainey (1956) and
Jones (1964) discussed the apparent in-
ability of N. f. attwateri to extend its
range into superficially suitable habitat
in southeastern Nebraska; attwateri pos-
sibly is unable to move farther north be-
cause of the severity of the climate, espe-
cially in winter. Riparian habitats that
appear suitable for habitation by baileyi
are present in southern South Dakota,
but for some reason (possibly the ab-
sence of enough shelter during winter)
woodrats have not been found there.
Perhaps baileyi has been able to persist
in north-central Nebraska only in spe-
cially sheltered areas, the most important
element furnished by the canyons of the
Niobrara being protection from severe
winters rather than a relatively cool en-
vironment during hot, dry summers.
The Sub-boreal also may have iso-
lated N. f. campestris from N. f. attwa-
teri, and the two probably were disjunct
for an extensive period. Contact may
have been reestablished in the relatively
warm moist Sub-Atlantic, broken again
during the dryer Scandic, and not rees-
tablished until European man fostered
the spread of riparian and other wood-
land habitats in north-central Kansas. Al-
though the two subspecies appear to
have been separated for a lengthy pe-
riod, they are presently in contact. Dur-
ing the dry Scandic and possibly during
other periods as well, it appears that
campestris was distributed in an un-
known number of small isolated popula-
tions in disjunct and probably marginal
habitats.
Since the time of initial isolation, the
submetacentric Y chromosome appar-
ently became fixed in baileyi, but the
translocation obviously had occurred
prior to isolation as it is seen also in
campestris and in attwateri from north-
eastern Kansas. Origin of the 6? hemo-
globin locus also occurred prior to the
time of isolation, because the £* allele
is seen in all three of the western sub-
species of floridana. During the warm,
wet Neo-Atlantic and since that time,
campestris probably has dispersed some-
what from the isolated, relict populations
of the Scandic, but continues to occur
in relatively disjunct, semi-isolated pop-
ulations.
With the possible exception of N. m.
micropus and N. m. planiceps, 1 doubt
that any of the populations of micropus
have evolved long in isolation from other
members of the species. Variation in
size and color both are clinal, the chro-
mosomal polymorphism involving num-
ber of large biarmed elements has been
observed at localities from which signifi-
cant numbers of woodrats have been
karyotyped (the only exception is N. m.
micropus from north of Ciudad Victoria,
Tamaulipas), and no marked changes
in hemoglobin phenotypes were observed
in northern populations of the species.
Neotoma micropus and N. floridana
apparently evolved in the classical man-
ner during the Pleistocene as a result of
isolation during glacial advance. Al-
though two species in my _ estimation,
they are closely related, recently evolved,
and retain limited genetic compatibility.
It is impossible to define precisely at
what stage two evolving phena should
be called species, but as I understand
floridana and micropus the process of
WOODRATS (GENUS NEOTOMA) IN CENTRAL NORTH AMERICA 165
evolution almost certainly has reached a
point in time whereby irreversible dif-
ferentiation has taken place. Although
micropus and floridana apparently did
not evolve exactly according to the stasi-
patric model (White et al., 1967; Key,
1968), they are stasipatrically distributed
today and apparently are continuing the
process of speciation in a manner similar
to that seen in morabine grasshoppers,
for which this model was proposed. That
is, the two species are in contact and
form a tension zone wherein hybrids
with reduced viability are produced.
This tension zone undoubtedly shifts
slightly within the deciduous forest-
grassland ecotone in response to environ-
mental changes. Introgression of a few
advantageous genes may be occurring in
one or both species as a result of hy-
bridization within the tension zone, but
clearly introgression (if it has occurred
at all) has been limited and mostly pre-
vented by rigid selection.
166 MISCELLANEOUS PUBLICATION MUSEUM OF NATURAL HISTORY
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