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NATURAL HISTORY SURVEY

FIELDIANA * ZOOLOGY

3- Published by

CHICAGO NATURAL HISTORY MUSEUM Volume 31 OCTOBER 6, 1947* No. 20

THE DISTRIBUTION OF LEUROGNATHUS

A Southern Appalachian Genus of Salamanders

CLIFFORD H. POPE

CURATOR, DIVISION OF REPTILES AND

NELSON G. HAIRSTON

NORTHWESTERN UNIVERSITY INTRODUCTION

The speciation of the southern Appalachian Plethodontidae presents many interesting zoogeographic problems. This speciation is evidently correlated with long isolation on these ancient, deeply eroded highlands. Nowhere else are the results of salamander evolution so plentiful. The over-all picture is extremely complex and can hardly be understood until the component parts have been studied individually and intensively. The genus Leurognathus, with its two forms, is one of these parts well suited for intensive investigation because of its relative simplicity. Moreover, its range is confined to the region and its derivation from Desmognathus certain.

It is but recently that sufficient locality records of this rare genus have warranted a comprehensive study. Discoveries of the last few years convince us that the approximate total distribution is now known.

DISTRIBUTION

The first specimen of the genus Leurognathus was collected on Roan Mountain, Carter County, Tennessee, by Rhoads in 1895, but was listed as Desmognathus nigra (= D. quadramaculatus) . Rhoads should not be severely censured for this mistake because similar ones are still being made. These mistakes emphasize the striking superficial similarity between species of the two genera. Only the most experienced and painstaking workers can recognize Leurognathus without difficulty.

No. 607 155 THE UBRASY Or THE

OCT 241947

NATURAL UNIVERSITY OF ILLINOIS

HISTORY SURVEY LIBRARY

156 FIELDIANA: ZOOLOGY, VOLUME 31

This genus was not described until 1899, when Moore erected it on the basis of three specimens collected by him in Avery County, North Carolina, on the southern flank of Grandfather Mountain, at an altitude of 3,500 feet. 'No further material was reported until 1917. In that year Dunn collected a larva at Pineola, Avery County, which led to recognition of Rhoads' Roan Mountain specimen, and one from Blowing Rock, Watauga County, overlooked by Moore himself. These facts were brought out in two papers by Dunn and one by Fowler and Dunn, all published in 1917. The range of the genus was greatly extended by the next specimen collected. This was reported by Dunn in 1924 from Jones Cove, Haywood County, North Carolina.

With the exception of five topotypes collected by Bishop and reported by him in 1924 and a series of 28 from the region of the type locality (Boone Fork, Watauga County) collected and reported in 1924 by Pope, no further material was found until 1927. The mono- typic status of the genus was changed in 1928 by Pope, who described the series he collected in 1927 at and near Davis Gap, Haywood County, North Carolina, as Leurognathus marmorata intermedia. Later in the same year Bishop reported a salamander from Frying Pan Mountain, also in Haywood County, as L. marmorata. This individual has subsequently (Bishop, 1943) been referred to inter- media; Dunn's Haywood County marmorata long ago met the same fate (Pope, 1928).

Only a few distributional records of the genus remain to be enumerated. In 1937 Bailey extended the range of marmorata to the following North Carolina localities: Montreat, Buncombe County; Ramsaytown, Yancey County; two localities near Linville Falls, one in McDowell County and one in Burke County. King in 1944 reported intermedia from these three places in the Great Smoky Mountains: Abrams Creek and Cades Cove, Blount County, Tennessee, and Smokemont, Swain County, North Carolina. He believed these to be the first Tennessee records of the genus, evidently because of the confusion resulting from the straddling of the North Carolina-Tennessee line by Roan Mountain, where Rhoads obtained the first specimen.

In giving the generic range in his handbook (1943) Bishop includes Caldwell, Henderson, and Haywood counties, North Caro- lina, in the distribution of marmorata but adds no further details. We learn from him (letter of June 10, 1947) that the Caldwell County series in the United States National Museum was taken 9J^ miles

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southwest of Blowing Rock; the Henderson County record is based on a larva (78 mm. long) from Stony Mountain, which lies about three miles northwest of Hendersonville and reaches an altitude of 2,843 feet. His listing of marmorata from Haywood County actually refers to an old record of intermedia from there.

Recent field work by both of us and examination of series of " Desmognathus" in the Chicago Academy of Sciences1 and Chicago Natural History Museum have brought to light important new material. In the summer of 1946 the range of intermedia was extended to extreme northeastern Georgia, when Whitney Pope secured a large specimen near Mountain City, Rabun County. Another was caught on Standing Indian, a mountain about twenty miles to the northwest but in North Carolina. These are now C.N.H.M. 47771 and 47772, respectively. Examination of the Museum series referred to above revealed seventeen Great Smoky Mountains specimens of intermedia masquerading as species of Desmognathus; all came from the immediate vicinity of Greenbrier Cove, Sevier County, Tennessee. Hairston collected marmorata at Duncan Cove Creek in western McDowell County, North Carolina, near the Yancey County boundary.

All of the locality records enumerated above are shown on the spot map. A study of the map reveals two facts about the two sala- mander populations hitherto designated as L. m. marmorata and L. m. intermedia: they are discrete and both are confined to the mountains. The only physical separation of the two populations is the valley of the French Broad River. Although this river, which in our area flows at relatively high elevations (about 2,000 to 1,200 feet), would not seem to be a serious barrier to a mountain stream salamander, the fact remains that it does divide them. Further- more, Leurognathus is not the only plethodontid genus in which this phenomenon occurs: Pseudotriton ruber nitidus and P. r. schenckii are separated by the same valley. It is also interesting to note that the range of Plethodon yonahlossee ends with this valley.

The range of Leurognathus is confined to the southern part of the Blue Ridge Province. In contrast to this correlation with physiog- raphy, we find no watershed correlation, both forms being found in Atlantic and Gulf drainages.

We feel that the records on our map approximately delimit the total range of the genus because (1) to the northeast, extensive col- lecting by various experienced herpetologists at White Top Moun-

1 We are indebted to Director Howard K. Gloyd for his generous cooperation.

POPE AND HAIRSTON: DISTRIBUTION OF LEUROGNATHUS 159

tain, Virginia, has failed to reveal specimens; (2) to the southwest, in the region of Copperhill, Tennessee, the vegetation has been destroyed; (3) elsewhere the natural habitat of the salamanders is eliminated with the abrupt change in physiography. Further col- lecting in Transylvania, Henderson, Buncombe, and Madison

6000

5000'

4000'

3000

2000

1000'

intermedia

marmorata

1

FRENCH BROAD RIVER

FIG. 29. Vertical distribution of the species of Leurognathus (approximate altitudes in feet).

counties (all outlined on the map) will test the validity of the French Broad Valley as a natural boundary separating the two forms.

ECOLOGY

Little is known of the ecology of Leurognathus. This ignorance stems partly from the comparative rarity of both forms, and partly from the fact that most collectors have been interested only in distribution. All observers are agreed that the genus is purely aquatic; no specimen has ever been taken elsewhere than in mountain streams, not even along the banks under rocks such as form typical hiding places for several species of Desmognathus. .Leurognathus marmorata has been recorded solely from the larger streams, whereas intermedia was first collected from a bare trickle (Dunn, 1924), and

160 FIELDIANA: ZOOLOGY, VOLUME 31

later observers have tended to confirm a preference for the smaller streams. Although this is' an inconsequential difference in itself, possibly there is a correlation with other more basic ecological separations; different types of food is one worthy of investigation.

Furthermore, intermedia would seem to be the more tolerant of variations in altitude, both high and low (see fig. 29); until now, marmorata has been reported only from altitudes between 3,000 and 4,000 feet, whereas intermedia has been found from 1,700 (King, 1944) to 5,400 feet (Bishop, 1928). The upward distribution of marmorata may well be limited by the small creeks at higher eleva- tions, a factor that would not affect intermedia. However, it is difficult to account for its absence from apparently acceptable streams at lower elevations than those reported. The single low- altitude record (1,900 feet) of marmorata given herein might be a specimen washed down in the severe flood that occurred four months earlier. An important limiting factor could be the preference of herpetologists for the higher elevations, particularly on Grand- father Mountain, where the road is placed conveniently at 4,000 feet, and high-altitude desiderata, such as Plethodon welleri, tempt the collector to ascend the mountain rather than to go down its more precipitous slope below. Perhaps a more thorough search along the foot of the Blue Ridge escarpment would bring more low- altitude specimens to light, just as similar collecting on the west face of the Smokies has recently revealed the presence of intermedia.

The breeding habits of L. marmorata are much like those of Desmognathus quadramaculatus (Pope, 1924), and L. intermedia probably will prove to have similar ones.

TAXONOMY

The nineteen specimens of intermedia that inspired this paper have been discussed in a preceding section. Their characters are listed in the table. All fall within the recorded size range. Six of the nineteen have vomerine teeth, and this character is not correlated with sex; both sexes thus show a lower incidence than in the type series, a difference that is not significant. The dorsal pattern proves to be surprisingly diagnostic, 74 per cent showing the two rows of light spots. Those without spots are immaculate brown above. No indication of the zigzag design of marmorata is evident.

In the twenty years since the description of intermedia no inter- grades have been reported. For this reason we are raising this form to specific rank. Those who do not regard intergradation as an

POPE AND HAIRSTON: DISTRIBUTION OF LEUROGNATHUS 161

CHARACTERS OF Leurognathus intermedia

C.N.H.M. 47771 from Mountain City, Georgia; C.N.H.M. 47772 from Stand- ing Indian Mountain, North Carolina; others from Greenbrier, Tennessee.

The costal grooves include one in the axilla and two in the groin; the inter- costal spaces are counted between the tips of the adpressed toes.

Specimen no.

C.A.S. C.N.H C.N.H C.A.S. C.N.H C.A.S. C.N.H C.A.S. C.N.H C.A.S. C.A.S. C.A.S. C.A.S. C.A.S. C.N.H C.A.S. C.N.H C.N.H C.A.S.

1126

.M. 48102... .M. 48105...

1143

M. 48101...,

1145

.M. 47771...

1089

.M. 47772...

1128

1129

1125

1141

1140

.M. 48106...

609

,M. 48104... .M. 48103... 9263..

Sex

.cP G?

Total

length

(in mm.)

95

90

73

68

57

50

111

?

105 103 102

90

88

85

83

82

77

75

65

Snout to

vent length

(in mm.)

50 47 40 38 32 31 62 57 56 55 55 47 48 45 45 44 42 40 34

Vomerine teeth R L

1 1

0 0

00 00 00

1 2 00 00 23 00 00 20 00 00 00 10 00 00 11

Costal grooves

14

14 14 14 14 14 14 13 14 15 13 14 14 14 14 14 14 14 13

Inter- costal Rows dorsal spaces white spots

2

2

0

2 (dim)

2

2 (dim)

2

0

2 (dim)

2

2

0

2

0

2 (dim)

Tail only

0

2 (dim)

2 (dim)

essential criterion of subspecific status will no doubt continue to regard intermedia as a subspecies, a position to which we do not seriously object.

DISCUSSION

Desmognathus quadramaculatus, obviously the closest living relative of Leurognathus, has been assumed to be its direct ancestor by Dunn, Noble, and others. Ecologically, Leurognathus is a com- pletely aquatic extrapolation of D. quadramaculatus. This fact is borne out by morphological characters: flattened skull, lack of vomerine teeth, more lateral location of the internal nares. We interpret the flattened head as an adaptation to bottom-crawling habits. The relative position of the two species of Leurognathus is clear: intermedia, with vomerine teeth and a simple pattern, is an early step, whereas marmorata is the end product. The wider vertical range of intermedia bears this out, indicating greater tolerance of a less specialized species. The larger size of marmorata is not a valid contradiction of this explanation, as size may have been secondarily acquired in correlation with a preference for larger streams.

162 FIELDIANA: ZOOLOGY, VOLUME 31

REFERENCES

BAILEY, J. R.

1937. Notes on plethodont salamanders of the southeastern United States. Occ. Pap. Mus. Zool., Univ. Mich., 364, pp. 1-10.

BISHOP, S. C.

1924. Notes on salamanders. Bull. New York State Mus., 253, pp. 87-102,

3 pis. 1928. Notes on some amphibians and reptiles from the southeastern states

with a description of a new salamander from North Carolina. Jour. Elisha

Mitchell Sci. Soc., 43 (3 and 4), pp. 153-170, pis. 23-26.

1943. Handbook of salamanders. Comstock Publ. Co., Ithaca, N. Y. xiv + 555 pp., 144 figs., 56 maps.

DUNN, E. R.

1917a. The salamanders of the genera Desmognathus and Leurognathus. Proc.

U. S. Nat. Mus., 53, pp. 393-433. 1917b. Reptile and amphibian collections from the North Carolina mountains,

with especial reference to salamanders. Bull. Amer. Mus. Nat. Hist., 37,

pp. 593-634, pis. 57-61.

1924. A new specimen of Leurognathus marmorata. Copeia, 127, pp. 31-32. 1926. The salamanders of the family Plethodontidae. Smith Coll. Anniv. Publ.,

Northampton, Mass, viii + 441 pp., 3 pis., 86 maps.

FOWLER, H. W. and DUNN, E. R.

1917. Notes on salamanders. Proc. Acad. Nat. Sci. Phila., 1917, pp. 7-28, pis. 3-4.

KING, WILLIS

1944. Additions to the list of amphibians and reptiles of Great Smoky Moun- tains National Park. Copeia, 1944, p. 255.

MOORE, J. P.

1899. Leurognathus marmorata, a new genus and species of salamander of the family Desmognathidae. Proc. Acad. Nat. Sci. Phila., 1899, pp. 316-323, pi. 14.

POPE, C. H.

1924. Notes on North Carolina salamanders with especial reference to the egg- laying habits of Leurognathus and Desmognathus. Amer. Mus. Nov., no. 153, pp. 1-15, 2 figs.

1928. Some plethodontid salamanders from North Carolina and Kentucky with the description of a new race of Leurognathus. Amer. Mus. Nov., no. 306, pp. 1-19, 1 fig.

RHOADS, S. N.

1895. Contributions to the zoology of Tennessee. No. 1, reptiles and amphib- ians. Proc. Acad. Nat. Sci. Phila., 1895, pp. 376-407. '

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