Revision of North American Salamanders of the Genus Plethodon

Abstract

Systematic study of the North American salamander genus Plethodon reveals three major groups in the genus, designated the western plethodons, the eastern small plethodons, and the eastern large plethodons. The western plethodons occur in the northwestern United States and adjacent Canada and include five species (vandykei, larselli, dunni, vehiculum, and elongatus) in three species groups. Five species in three species groups also comprise the eastern small plethodons. Four of these (welleri, dorsalis, cinereus, and richmondi) occur in eastern North America; the fifth (neomexicanus) is known only from the Jemez Mountains of New Mexico. The eastern large plethodons include six species (wehrlei,yonahlossee, ouachitae, caddoensis, jordani. and glutinosus) in three species groups and occur only east of the Rocky Mountains. The eastern large and small plethodons are more closely related to each other than either is to the western plethodons, but of the two, the small group appears to be closer to the Western plethodons. Special emphasis has been placed on a study of geographic variation in pigmentation and segmentation characteristics of the eastern species. The use of the trinomen to describe geographic variation has been found unsatisfactory because of nonconcordance of geographically variable characters in species formerly considered polytypic. Seven isolated allopatric populations are still recognized as subspecies because of their apparent close relationship to the nominotypical subspecies, but the taxonomic status of each is still uncertain. Some of these forms are weakly differentiated and all are in need of further study.