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Full text of "Phytoneuron"

OBSERVATIONS ON FRAXINUS ALBICANS BUCKLEY (OLEACEAE), 
THE CORRECT BOTANICAL NAME FOR TEXAS ASH 

Guy L. Nesom 

2925 Hartwood Drive 

Fort Worth, TX 76109, USA 

www.guynesom.com 

ABSTRACT 

Fraxinus americana (eastern North America) and the closely similar Texas ash (Texas, 
southern Oklahoma, and north-central Mexico) have sometimes been considered to be conspecific, 
but they are treated here as distinct species. A key contrasting the features of each is provided and the 
county- level distribution of each is mapped; the distribution of F. americana is shown only for Texas 
and Oklahoma to indicate its parapatry with its close relative. Fraxinus albicans Buckley (1863) is 
the correct botanical name for the species previously identified as F. texensis (A Gray) Sargent 
(1894). Lectotypes are designated for F. albicans and for F. americana var. texensis A. Gray (= F. 
texensis). Photos of the types are provided. 
KEY WORDS: Fraxinus albicans, F. texensis. F. americana, Oleaceae 



Fraxinus texensis (A Gray) Sargent (Texas ash) was mapped by Turner et al. (2003) as a 
variety of F. americana L. (white ash), as originally described by Asa Gray. It was treated as a 
subspecies of F. americana by Miller (1955) but Correll and Johnston (1970), Simpson (1988), and 
Diggs et al. (1999) treated it at specific rank. Texas ash shares the distinctive abaxial leaf surface 
found in white ash (Hardin & Beckmann 1982; Williams & Nesom 2009) and also is similar in 
samara morphology, but Texas ash usually occurs in more xeri> habii !ts alone the western margin of 
white ash (Fig. 1) and is morphologically distinct. 

Miller (1955, p. 24) noted that at the southwestern extension of its range, typical Fraxinus 
americana "gives way" to Texas ash (identified by her as F. americana subsp. texensis) and that 
"since [Texas ash] is physiologically and ecologically separated from the white ash, and 
morphologically distinguishable, it is worthy of recognition beyond a mere variant of the white ash." 
She treated it at subspecific rank because "it apparently does hybridize on occasion with the white 
ash," listing four collections that she regarded as examples of such hybrids. Each of these four, 
however, was collected outside of the known range of Texas ash and none is likely to be such a 
hybrid. Schlesinger (1990) also noted, without documentation, perhaps based on the previous 
observations by Miller, that white ash and Texas ash intergrade. 

The present study corroborates previous observations that Texas ash and white ash are closely 
similar but discontinous in ecology and morphology. Populational variants within white ash 
sometimes approach Texas ash in features of fruit or leaf morphology, but it seems clear that two 
evolutionary entities exist. The two taxa are essentially allopatric or parapatric, with their ranges 
most closely in contact in south-central Oklahoma. White ash occurs in mesic valleys and bottoms in 
that area, and true genetic intergrades might be most successfully sought there. 

Differences between Texas ash and white ash, as the latter occurs in Texas and Oklahoma, 
are summarized in the following contrast. 



Nesom: Fraxinus albicans, the Texas £ 



1. Leaf scars 2.5-3(-4) mm wide, depressed obovate, the upper margin shallowly concave to slightly 
notched with slightly flaring margins; rachises ■ I— )2-6(— 7) cm: leaflet blades 3-6(-8) cm x 2-5 cm. 
usually suborbicular-ovate to obovate, oblong-ovate, or elliptic, apex abruptly acute to rounded; 
samaras (12-)15-26(-35) mm long, wings 3-5(-6) mm wide, bodies 5-8 mm long, 1.5-2(-3) mm 

wide Texas ash 

1. Leaf scars 3-4 mm wide, U- or crescent-shaped with a deeply concave or deeply notched apex and 
narrowly flaring margins; rachises 5-10 cm; leaflet blades 5.5-12(-15) cm x (2-)2.5-6(-7.5) cm, 
ovate to ovate-lanceolate, elliptic-lanceolate, or oblong-elliptic, apex acute to acute-acuminate or less 
commonly obtuse: samaras (19-)25-32(-38) mm long, wings 3-5(-6) mm wide, bodies (5-)6-ll 
mm long, 1.5-2.5 mm wide white ash 

Variation in samara morphology in an array from each taxon is shown in Fig. 2a and b. 

Fruits of white ash are from putatively diploid individuals from Texas, Oklahoma, and Louisiana. A 
small-fruited form of white ash occurs in scattered localities as variants in diploid populations (Fig. 
6), especially in southern states of the USA, and samaras at the small end of the size range for the 
white ash are much less common than samaras of typical size. Gray (1886, p. 75) commented that 
some small fruits of Froxinus americcma var, microcarpa A. Gray (the type from Alabama) were 
"seemingly full grown but seedless" — all small-fruited collections that I have seen, however, have 
produced fruits with bodies fully filled by embryos. 

Three levels of ploidy occur within Fraxinm americcma — diploids, tetraploids, and 
hexaploids — but only diploids reach westward and closely approach the range of Texas ash (Nesom 
in prep.). A chromosome number has not been reported for Texas ash. 

The geographic range of Texas ash is mostly along the eastern portion of the Edwards Plateau 
in Texas, northward into the Arbucklc Mountains regu.n of soulh-ccnttai OkLhoma, and southward 
into northern Coahuila and Nuevo Leon (Fig. 2). It occurs mostly on rocky slopes and bluffs or 
stream and in canyons and ravines, commonly with cedar elm, juniper, juniper-oak, post oak- 
blackjack oak, pine-hardwood, or oak-maple. Particularly large individuals of Texas ash are within 
Fort Worth, Texas, in areas of the Trinity River fioodplain that were intermittently flooded until the 
last 50 years — some of these trees reach nearly 70 feet in height and 100 inches (diameter breast high) 
in circumference. Typical individuals occur abundantly in nearby upland areas. White ash is 
widespread in the eastern North America and characteristically occurs in mesic hardwoods 

^. •IlllllllllllKv <'ll ^l.'|K^ jikI 11. ih 

Plants in the Davis Mountains of trans-Pecos Texas (Jeff Davis Co.) identified by Palmer 

(1929, p. 42) as Fraxinm texensis, "the commonest species of ash in the Davis Mountains," instead 
are F. velutina Torrey (e.g., Palmer 30822, MO; Palmer 30797, GH, MO; Palmer 34343, GH; 
Palmer 34344, GH). Palmer also identified F. velutina as occurring in the Davis Mountains but did 
not specify his concept of the distinction between the two putative species. 

Vouchers for records of Texas ash in Mexico (as mapped in Fig. 1) are given here: Coahuila. 
W side of Potrero de la Mula, ca 20 km NW of Ocampo, on the escarpment near the mines, tree 10 
feet tall with oaks on N-facing middle slope, 18 Sep 1941, 1. M Johnston 9222 (GH) and tree 12 ft tall, 
frequent on N slopes along crest, 18 Sep 1941, I.M Johnston 9254 (GH); Sierra de Gloria, SE of 
Monclova, Jul 1939, Marsh 1870 (GH). Nuevo Leon. Mpio. Villaldama, Rancho Minas Viejas, 
camino hacia Las Pilas, bosque de Quercus, 1170 m, 16 Apr 2001, Estrada 12399 (BRIT-2 sheets). 



Nesom: Fraxinus albicans, the Texas £ 



The correct botanical name for the Texas ash. 

The names Fraxinus americana var. texensis A Gray (= F. texensis) and F. albicans Buckley 
have been closely associated in concept, as explained below, and their relationship to typical F. 
americana also lias been at issue. If the nomenclatural types of F. americana var. texensis and F. 
albicans are conspecific with each other and not conspecific with the type of F. americana, then F. 
albicans of 1863 is the correct name at specific rank for Texas ash, replacing Sargent's F. texensis (A. 
Gray) Sargent of 1894. 

Without clear typification, the application of Fraxinus albicans has been ambiguous. A 
possible course toward clarification is to lectotypify it with a specimen of typical F. americana, thus 
allowing retention of the long-used and geographically appropriate F. texensis for the primarily Texas 
trees. The most justifiable interpretation of protologues and specimens, however, as detailed below, 

indicates that F. albicans is the correct botanical name for the Texas ash and should be adopted. 

Potential type material for Fraxinus albicans at PH includes sheets with a mixture of the 
Texas ash, while ash with typical-sized fruits, and green ash (F. pennsylvanica Marsh). The mixtures 
of species were assessed and annotated in 1996 by Achinelli-Delucchi, working out of the Museo de 
la Plata (LP). 

PH-1070637 (Fig. 3): Texas ash, 1 fruiting branch, 2 detached leaves; white ash, portion of 
infructescence, 1 detached leaf. Handwritten label by an unknown hand and above it a 
shorter one written by Buckley; on both labels, the handwritten epithet "negleet-a" (by 
Bucklej', with the strikethrough) was replaced immediately above il (also by Buckley) by 
"albicans." Buckley's handwriting is established by comparison with samples in Dorr and 
Nixon (1985). 

The label in unknown hand, probably referring to the detached leaf and 
infructescence (F. americana sensu stricto) immediately above it, has this: "No. 40. White 

ash, Fraxinus [Buckley's handwritten names j 1 am not certain that this is all of the family 

in our portion of Texas. It is one of our largest and useful timber trees; our wagons, buggies, 
plough stock, axe handles and and cotton baskets are composed of it. It makes our best 
flooring plank. To 100 ft. Blooms last of March." 

PH-1070637 was collected in Texas, and the small leaflets, characteristic petiole 
bases (leaf scars), and small iruits clearly save to identify this collection as Texas ash. 
Selected here as lectotype. 

PH-1070638: white ash, 1 fruiting branch, 1 detached leaf, one detached node with 2 leaves. 

Handwritten label by Durand(?) noting 'Fraxinus albicans Buckl.l & no mistake!!!"; the 
bottom of this label has Asa Gray's annotation of F. americana L.!" 

This plant has large fruits, relatively large ellliptic to elliptic-ovate leaflets, and 
petiole bases identifying it as typical white ash. Provenance not indicated. 

PH-1070639: Texas ash, 1 fruiting branch, on the right; F. berlandieriana DC, 1 fruiting branch. 
>miU ' iti'ajjttui lilel p llu- pipa b\ PiwJle\ is Frca i i ms Buckl., Texas," 

although the label is not unambiguously associated with one or the other of the branches. 

The branch of Texas ash on PH-1070639 could easily be from the same tree as the 
designated lectotype (PH-1070637) and is taken here to be an isolectotype. 

GH (Fig. 4): Texas ash, 2 detached leaves, 15 fruits. Written on the sheet by Asa Gray: '"F. 
albicans.' Buckley, the real, or one of them, i.e., reduced F. Americana. Texas. Buckley! ex 
spec, Durand. = F, Americana,? var. Texensis." Annotated by Miller in 1950 as "F. texensis 



Nesom: Fraxinus albicans, the Texas e 



The GH material probably was taken by Gray from the specimen designated here as 
lectotype of F. albicans (PH-1070637, loaned to Gray in 1862 and annotated by him as 
"Texas. Buckley! ex spec. Durand"), which has a large number of fruits, some attached to the 
infructescence and some loose. Taken here to be an isoleetotype. 

Asa Gray's involvement with the Texas ash began almost immediately after Buckley's 
publication. He borrowed material from PH and quickly published a commentary (Gray 1862). 

"Having for many years past taken a prominent part in the study of Texan botany, as made 
known by the ample collections of Berlandier, Drummond, Wright, Lindheimer, Thurber, and 
others, and being under the necessity of keeping, as nearly as possible, an courant with all 
publications upon the subject, I was naturally much interested in the appearance of Mr. 
Buckley's two papers, and not a little surprised at the large number of new species which he 
had gleaned in such a well -harvested field. Accordingly I applied for specimens of the plants 
in question; and Mr. Buckley — an early correspondent of Dr. Torrey and myself — promptly 
and obligingly has placed in my hands, for examination, nearly the whole original materials 
upon which these new genera and species were characterized." [p. 1 61] 

"Turning to Mr. Buckley's Texan specimens [of Fraxinus] in the herbarium of the Academy, I 
find there are two, both in fruit; one with the larger larves and fruit is clearly F. viridis, var. 
Berlandieriana, Torr., Bot. Mex. Bound. (F. Berlandieriana DC); the other is, I think a form 
of F. Americana (i.e., albicans of Buckley), of the small-fruited form we are familiar with, but 
with very small leaves as well as fruits, the latter terete and cylindrical in the manner of the 
species." [p. 166] 

Thus it appears that Gray studied at least PH-1070639. The material for the GH isoleetotype 
of Fraxinus albicans either was sent to GH as a gift, or it could have been taken from PH-1070637, 
which has a large number of fruits, some attached to the infructescence and some loose. In any case, 
Gray's assessment at the time was that the Texas ash should be identified as F. americana and he 
roundly castigated Buckley, noting that he "had no need to give a new specific name to the white 
ash." Later, Gray (1886) did recognize the Texas ash as a distinct entity. 



Fraxinu*. albicans Buckley, Proc. Acad. Nat. Sci. Philadelphia 14; 4. 1862. Frax. 

albicans (Buckley) Lingelsh., Mitt. Deutsch. Dendrol. Ges. 1911: 184. 1911. LECTOTYPE 
(designated here; Fig. 3): USA. Texas. No other information, S.B. Buckley s.n. (PH-1070637 
digital image!; isolectotypes: GH! "ex spec. Durand" (Fig. 4). PH-1070639 digital image!). 
See detailed notes below regarding the lectotype, isolectotypes, and other type material. 
Miller (1955, p. 36) noted that the type of F. albicans ["in part"] was at PH but did not cite or 
allude to any particular specimen or collector. 

Protologue (excl description): "It is found from New England to Texas, being the 
largest of the American ash trees, sometimes attaining a diameter of between four and live 
feet. Its bark is furrowed and of a light grey; hence it is called the white ash in many places. 
Its petioles are grooved, and its buds are destitute of the red velvety pubescence peculiar to F. 
americana. I have not seen it in the vicinity of Phildelphia, nor is there any specimen of it 
collected in mis neighborhood in the herbarium of the Academy. In the herbarium of 
Darlington, at West Chester, I saw specimens of it labelled F. americana, and it is probably 
thus called by other American botanists. The West Chester collection had no specimens of F. 
americana or F. pubescens. [paragraph] Both F. americana and F. albicans being called 
white ash throughout the counry have caused them to be confounded, especially where, as is 
often the case, they do not both grow in the same locality; but the fruit of the latter is only 
about half the size of the former, which, with the other distinctions enumerated, show that 
they are very different species." 



Nesom: Fraxinus albicans, the Texas £ 



Fraxinus americcma var. texensis A. Gray, Syn. Fl. N. Amer. (ed 2) 2(1): 75. 1886. Fraxinus 
texensis (A Gray) Sargent, Silva 6: 47. 1894 [nom. superfl. illeg., in the interpretation here 
that it is conspecific with Fraxinus albicans Buckley 1862 ]. Fraxinus americana subsp. 
texensis (A Gray) G.N. Miller, Cornell F.xpt. Station 335: 36. 1955. LECTOTYPE 
(designated here; Fig. 5): USA. Texas. [Val Verde Co.:] Canon of Devil's River, 16 Sep 
1852, J.M. Bigc.'Ai ,;. lull' isolectotype N"\ digital image!). The GH sheet is annotated 
in Gray's handwriting, on a "Syn. Fl. N. Amer." annotation label, as "F. americana var?. 
texensis." 

Protologue (exci. description): "F albicans, Buckley, 1. c, in part. F. pistaciaefolia, 
E. Hall, List. PI Tex. no. 527. F. coriacea, Watson, 1. c, as to pi. Bigelow, "Devil's Run 
Canon," Texas (not "Arizona"). . . . Texas, on rocky hills, from Austin to Devil's River, near 
the Rio Grande Pe lups a di \vaJt species \ s\ ir\pc is in m liaM Co.: Austin, rocky 
hill, 13 May 1872, E. Hall 527 (GH!, NY digital image!). 

An internal contradiction in Buckley's protologue for Fraxinus albicans causes a difficulty in 
interpretation. Buckley noted that F. albicans is a large tree ranging widely in eastern North 
America — this does not characterize the Texas ash, in which the trees are mostly relatively smaller in 
size and geographically restricted. In contrast, he observed that the fruits of F. albicans are about half 
the size of those of F. americana — this is truer of the Texas ash, although atypically small fruits also 
are produced in scattered localities in typical F. americana over its wider range (see comment below). 
From the protologue observations, it appears that Buckley's concqjt of F. albicans included the Texas 
ash and the small-fruited forms of typical F. americana. In Buckley's type material of F. albicans, 
however, the small-fruited form is represented only by trees of the Texas ash. Typical F. americana 
is represented (on two of the Buckley sheets at PH) by trees with larger fruits. 

In the original description of Fraxinus americana var. texensis, Gray (1886, p. 75) cited "F 
albicans. Buckle}', I.e., in part" as a synonym. Immediately above, on the same page, he cited "F 
albicans, Buckley in Proc. Acad. Phiiad. 1862, partly" under F americana var. microcarpa .A Gray. 
Gray's partition of the concept of F. albicans appears to reflect his understanding that the taxon in the 
sense of Buckley's protologue and type material included an entity from Texas as well as from the 
eastern USA Gray's comments of 1886 did not refer to a specimen, but he had seen at least one of 
the associated Buckley collections from PH (see comments above regarding the GH isolectotype of F 
albicans) and acquired for GH a sample of fruits and leaves representing the Texas ash. Gray clearly 
associated Buckley's type material with the Texas ash, the Texas "part" of the F albicans concept. 
The other "part," var. microcarpa, will be lectotypified by a Curtiss collection from Alabama (Nesom 
in prep.), which represents a small-fruited populational variant of typical F. americana (see example 
in Fig. 6). 

When Sargent (1894) raised Fraxinus americana var. texensis to specific rank, he cited in 
synonymy "Fraxinus albicans. Buckley, Proc. Phil. Acad. 1862, 4 (in part)," repeating Gray's 
partitioned concept. Because the correspondence was clear between var. texensis and its associated 
"part" of F albicans, Sargent's use of F texensis at specific rank is interpreted here as a superfluous 
substitution for the earlier F. albicans, rendering his combination illegitimate. Lingelsheim (1907, 
1920) and Miller (1955) also have considered F albicans conspecific with F americana. Miller 
repeated the "F albicans Buckley in part'" phrasing in listing it as a synonym, but Lingelsheim (1920) 
recognized F. americana var. albicans and unequivocally cited F. albicans Buckley and F ( 
var. texensis A. Gray as synonyms. 



Nesom: Fraxinus albicans, the Texas £ 



ACKNOWLEDGEMENTS 

I am grateful to the staffs at BRIT/SMU/VDB, GH, MO. NLU, OKL. OKLA, and TEX/LL 
for help during visits to those herbaria, Mike and Shirley Powell (SRSC) for information and photos 
of trans-Pecos plants, Nancy Elder (UT-Austin Life Sciences Library) for help with literature, John 
Strother for detailed comments and salutary suggestions, and staffs of GH and PH for providing 
images of the types of Fraxinus albicans and F. americana var. texensis. This study was done in part 
under contract for the Flora of North America Association, in conjunction with preparation of the 
FNANM treatment of Fraxinus. 

LITERATURE CITED 

Buckley, S.B, 1 862. Notes on some of the American Ash Trees, (Fraxinus,) with descriptions of new 

Species. Proc. Acad. Nat. Sci. Philadelphia 14: 2-5. 
Correll, D.S. and M.C. Johnston. 1970. Manual of the Vascular Plants of Texas. Texas Research 

Foundation, Renner. 
Diggs, G.M., B.L. Lipscomb, and R.J. O'Kennon. 1999. Shinners & Mahler's Flora of North Central 

Texas. Botanical Research Inst, of Texas, Fort Worth. 
Dorr, L.J. and K.C. Nixon. 1985. Typification of the oak (Quercus) taxa described by S.B. Buckley 

(1809-1884). Taxon 34: 211-228. 
Gray, A. 1862. Notes upon the "Description of New Plants from Texas, by S.B. Buckley," published 

in the Proceedings of the Academy of Natural Sciences of Philadelphia, Dec. 1861 and Jan. 

1862. Proc. Acad. Nat. Sci. Philad. 14: 161-168. 
Gray, A. 1886. Oleaceae. Synopt. Fl. N. Amer. (ed. 2), vol. 2, part 1: 72-79. 
Hardin, J.W. andR.L. Beckmann. 1982. Atlas of foliar surface features in woody plants: 5. Fraxinus 

(Oleaceae) of eastern North America. Brittonia 34: 129-140. 
Lingelsheim, A. 1907. Vorarbeiten zu einer Monographic der Gaining Fraxinus. Bot. Jahrb. 40: 

185-223. 
Lingelsheim, A 1920. Oleaceae-Oleoideae-Fraxineae. In: A Engler (ed.), Das Pflanzenreich IV. 

243: 1-61. 
Mller, G.N. 1955. The genus Fraxinus, the ashes, in North America, north of Mexico. Cornell. 

Expt. Sta. Memoir 335, Cornell Univ., Ithaca, New York. 
Palmer, E.J. 1929. The ligneous flora of the Davis Mountains, Texas. J. Arnold Arbor. 10: 8^15. 
Sargent, C.S. 1894. Fraxinus texensis. Silva N Amer. 6: 47^18, plate 270. 
Schlesinger, R.C. 1990. Fraxinus americana L. White Ash. Pp. 333-338, in R.M. Burns and B.H. 

Honkala (tech. coords.). Silvics of North America. Volume 2. Hardwoods. USDA Forest 

Service Agric. Handbook 654, Washington, D.C <http://willow.ncfes.umn.edu/silvics_manual/ 

volume _2/fraxinus/americana.htm> 
Simpson, B.J. 1988. A Field Guide to Texas Trees. Texas Monthly Press, Austin. 
Turner, B.L., H. Nichols, G.C. Denny, and O. Doron. 2003. Atlas of the Vascular Plants of Texas, 

Vol. 2. Sida, Bot. Mscell. No. 24. 
Williams, J. and G.L. Nesom. 2010. The status of Fraxinus papillosa (Oleaceae): SEM study of 

abaxial epidermal features. Lundeliia, submitted. 




Fraxinus americana 
• Fraxinus albicans 



Figure 1. Distribution of the Texas ask Fraxinus albicans (see text regarding the epithet). The 
distribution of F. americana is shown for Texas and Oklahoma to indicate its parapatry with F. 

albicans. 



: frawiu? tibicans. die Texas a 



\s\w\mw 




Figure 2. Samara 
Oklahoma. Bottor. 
Oklahoma, and Lo 



on Top two rows;, Texas ash {Fraianus albicans) in Texas and 
ows, typical diploid white ash (Fraxinus americana) in Texas, 







Figure 3. Lectotype of Fraxinus albicans (PH). Detatched leaves at bottom right and top left, 
fruiting branch, loose fruits. See comments in text. 



Nesom: Fraxinus albicans, the Texas e 




Figure 4. Isolectotype of Fraxinus albicans (GH). Sec comments in text- 



Nesom: Fraxinus albicans, the Texas e 




Figure 5 . Lectotype of Fraxinus americana var. texensis (GH). See comments in text. 




(from Morgan Co., Tennessee). Such 
crocarpa (see text).