The Relationships of the Salamanders of the Genus Plethodon
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THE RELATIONSHIPS OF THE SALAMANDERS OF THE GENUS PLETHODON By RICHARD HIGHTON A DISSERTATION PRESENTED TO THE GRADUATE COUNCIL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA June, 1956 iifipiili J 1262 08552 2885 tablh; op contents Page INTHOOliCTION . 1 MRHDB0 5> THE RELATION BETWEEN NUMBER OF COSTAL GROOVES AND TRUNK VEitTEBRAE IN PLETHODON 8 PIGMENTATION IN THE GENUS PLETHODON 12 TOO. TO THE SAIAtANDl&b OF 98 GENUS PLBTHODOM lU STSTSttTICS 20 The Western Plethodons 29 Plethodon vandykei Group . 3h Plethodon vandykei vandykei Van Denburgh .... 35 Plethodon vandykei idahoensis Slater and Slipp . 37 Flethodon vandykei larselli Burns . 37 Plethodon vehiculum Group 38 Flethodon dunni Bishop ....... 38 Plethodon vehiculum (Cooper) Ill Plethoaon productus Croup ,. k3 Plethodon productus , new nans 1*3 Plethodon neomexicanus Group • U6 Plethodon neowexicanus Stebbins and Riemer .... U6 The Eastern Small Plethodons U7 Plethodon wclleri Group 5l Flethodon welleri Valker 5l Plethodon richraondi richmondi Netting and Mittleran 61 Plethodon richraondi popei 1 ighton and Grobman . 62 Plethodon richmondi netting! Green .. 6U ii Plethodon cinereus Group . 65 Plethodon dorsalls dorsalla Cope ........ 68 Plethodon dorsalis angusticlavius Grobman .... 71 Plethodon cinereus cinereus (Green) . 76 Plethodon cinereus serratug Grohman 78 Plethodon cinereus polycentratus Highton and Grobman 79 The Eastern Large Plethodons 80 Plethodon wehrlei Group 90 Plethodon wehrlei welirlei Fowler and Dunn .... 93 Plethodon wehrlei dixl Pope and Fowler ..... 96 Plethodon wehrlei jacksoni Newman ........ 96 Plethodon yonahlossee Group 97 Plethodon yonahlossee Dunn ........... 100 Plethodon ouachitae Dunn and Keinse ....... 103 Plethodon caddoensis Pope and Pope ....... 105 Plethodon glutinosus Group . 106 Plethodon jordani jordani Blatchley 129 Plethodon jordani metcalfj Brimley 132 Plethodon jordani shermani Stejneger 13k Plethodon jordani unicoi, new subspecies .... 135 Plethodon jordani raelaventris Pope and Hairston . 136 Plethodon jordani rabunensis Pope and Hairston . 138 Plethodon jordani teyahalee Hairston 1U0 Plethodon jordani clamsonae Brimley lUl Plethodon glutinosus glutinosus (Green) 193 Plethodon glutinosus albagula Grobman . 196 SUM3ART 197 LITERATURE CITED 198 iii LIST OF FIGURES Figure Page 1. Lateral and dorsal views of the trunk vertebrae of representatives of the three major groups of the genus Plethodon 23 2. Suggested phylogeny of the major subdivisions of the genus Plethodon , 26 3. Suggested phylogeny of the Western Plethodons 33 U, The distribution of the subspecies of Plethodon vandykei in Washington, Oregon, and Idaho. 36 5. The distribution of Plethodon dunni in Oregon and southwestern Washington, . Uo 6. The distribution of Plethodon vehiculum in Oregon, Washington, and British Columbia . U2 7. The distribution of Plethodon productus in California and Oregon US 8. The distribution of Plethodon neomexicanus in New Mexico h.5 9. Suggested phylogeny of the Eastern Small Plethodons ... 5>2 10. The distribution of Plethodon welleri in North Carolina, Tennessee, and Virginia. 52 11. The distribution of the subspecies of Plethodon richmondi 63 12. The distribution of the subspecies of Plethodon dorsalis . ....... 70 13. The distribution of the subspecies of Plethodon cinereus 77 Hi. Vomerine teeth of ?6° peninsula Florida P. glutinosus plotted against snout-vent length. .7 83 15. Vomerine teeth of \& P. glutinosus from the Coastal Plain of Virginia and North Carolina plotted against snout-vent length. ... ... 83 16. Vomerine teeth of ll£ P. j. jordani plotted against ."" snout-vent length. 8U It Figure Page 17. Vomerine teeth of 60 P. w. wehrlei plotted against snout-vent length 8ii 18. Vomerine teeth of 39 P. caddoensis plotted against snout-vent length 85> 19. Suggested phylogeny of the Eastern Large Plethodons ... 85 20. The distribution of the s\ibspecies of Plethodon v/ehrlei . 9$ The 21. distribution of the Plethodon yonahlossee Group . 102 22. The distribution of the subspecies of Plethodon jordani . 112 23. The distribution of the dark-chinned ( glutinosus ) and light-chinned ( albagula ) populations of P. glutinosus in central Texas . 189 2U. The distribution of Plethodon glutinosus in eastern United States 195 INTRODUCTION The North American renus Flethodon presently has more recog- nised forms than any other genus of salamanders. It is the type genus of the lungless family Plethodontidae, reviewed so ably by Dunn in 1926. At present, this is the most successful salamander family; over half of the living species of the Order Caudata are plethodontids . North Amer- ica is the center of the distribution of the family, but one genus, Hydromantes , also occurs in Europe, and members of several genera enter the Neotropical region. Salamanders of this family occupy habitats ranging from strictly aquatic cavernicoles ( lyphlomolge and haideotriton ) and mountain stream dwellers ( Leurognathus ) to others like i'lathodon , which are completely terrestrial, even to the ex-bent of laying their eggs on land. Dunn believed that Plethodon is the most primitive genus in the attached-tongue branch of the family, and that Hemidactyiium , fesatina , Batrachoseps , and Aneides are more specialised deriv?tives of a Plethodon- like ancestor. In 1926, only eleven forms of Plethodon were known to Dunn. In 19U3> Bishop listed 17 species (one has since been removed from the genus) and two subspecies (both are now considered different species). In 19UU, Grobman reviewed the distribution and relationships of the eastern section of the genus, including some sixteen species and sub- species. There are now twenty-five forms recognized in eastern North America, with seven more in the western United States and Canada. Grobman (19U1a* 266) divided the eastern forms into two groups, the Large Plethodons and the Small Plethodons. He suggested that these - 2 - groups might actually represent distinct renera or subgenera, but he reserved Judgement in this matter until the relationship of the west- ern species with the eastern forms could be determined. One of the purposes of the present study is to determine these relationships by a comparative study of the morphology of all the species of the genus Plethodon. Of the twenty-five genera in the family Plethodontidae, only two others show as great or greater disjunctions in their distribu- tions as that found in Plethodon , These are hydromantes , with two forms in Europe and three species in California, and Aneides , with four species in western North America and one in the Appalachian Moun- tains of the eastern United States. In the past two decades, several new plethodons have been discovered in both eastern and western North America. A review of the relationships of these forms offers a valu- able opportunity to study the evolution of this important group of North American salamanders. The importance of exa'iining plethodons in life has been em- phasised by most recent workers, "wany species, particularly the Large Eastern forms, are extremely difficult to identify after years of pres- ervation. In few other vertebrates are differential characters between species so rare. For this reason, a special attempt was made to obtain living specimens of each form. Twenty-five of the thirty-two forms recognized herein have been studied nlive. The list of persons who have contributed specimens to this project is long and I wish to express to each of them my sincerest thanks and appreciation for their valuable aid: Charles G. Adams, - 3 - Ifclter Auffenberg, Herbert Barden, Albert P. Blair, E. E. Brown, Jerry and Esther Brown, Douglas U. Burns, Archie Carr, A. H. Chaney, llerndon Roger Conant, John '.V. Crenshaw, J. C. Dickinson, John Dolan, Dowling, Philip C. Dumas, Helen T. Gaige, M. Ruth Gilreath, Arnold B. Grobraan, T. P. Haines, Keith L. Hansen, Robert Hellraan, Albert H. nighton, Thelraa Howell, Leslie tfubricht, Robert Humphries, Richard M. Johnson, James Kezer, J. D. Kilby, James Knepton, H. D. Leake, Edwin H. McConkey, John S. Mecham, Sherman A. i&nton, .ilfred T. Heill, Howard T. Odum, Larry H. Ogren, David Pettus, John Quinby, George Rabb, Neil D. Richmond, .William Riemer, Bernard Roseman, Doug Rossrnan, Albert Schwartz, ilcbert S. Simmons, Ralph Sinclair, William Sloan, Peter Smith, Bette Starner, Charles J. Stine, Valter Stone, Virginia Switzer, Sam R. Telford, G. M. Thorp, Gordon Thurow, Don Tinkle, Arnold and Rusty Van Pelt, Charles P. talker, "illiam 'itt, and harry Yeatman, Most of the material given me by these persons has been deposited in the University of Florida collection. This collection has formed the nucleus of the material on which this study is based. Some additional specimens have been borrowed from other collections, but I did not attempt to follow the course of the conventional monog- rapher and examine every specimen available in museums, simply for the sake of completeness. The material borrowed from other museums in- cludes the following: Western Plethodons fron the University of California j Texas P. glutinosus from Bryce C. Brown, Ottys Sanders, John S. Mecham, and the Strecker lluseumj P. d. angusticlavius , F. of glutinosus , P. ouachitae , and P. caddoensis from the University Arkansas; P. c. serratus , P. w. wehrlei , and P. w. dixi from the -u- Chicago Natural History Museums P. glutinosus, P. w. wehrlei , and P. richmondi from the Carnegie Ifuseura; P. cinereus from the ?Juseura of Comparative