Woodland Salamanders Plethodon   Tschudi, 1838
An adult specimen of Plethodon websteri from Wilkinson County, Mississippi Image © Suzanne L. Collins, 2001
Taxonomic Comments:
Mahoney, Meredith J. (2001. Molecular systematics of Plethodon and Aneides (Caudata: Plethodontidae: Plethodontini): Phylogenetic analysis of an old and rapid radiation. Molecular Phylogenetics and Evolution. 18(2): pp. 174-188.), using mtDNA, presented clear evidence that the western U.S. species of Plethodon are a distinct genus. Abstract: The closely related salamander genera Plethodon and Aneides (Plethodontidae) differ in morphology, behavior, and ecology. Although the systematics of these taxa has been the focus of much study, many details remain unresolved. To generate an hypothesis for the relationships among these taxa, I sequenced a segment of the mitochondrial protein-coding gene ND4 and portions of mitochondrial tRNAs. Taxa sampled were 5 species of Aneides, 7 species of western Plethodon, and 13 species of eastern Plethodon. Ensatina eschscholtzii was used as the outgroup. Phylogenetic analyses using maximum-parsimony, neighbor-joining, and maximum-likelihood consistently recovered some relationships. The eastern species of Plethodon are a robust, well-supported clade. Sister taxon relationships of P. elongatus and P. stormi, of P. dunni and P. vehiculum, and of A. hardii and the three west coast species of Aneides were also consistently resolved with good support. The monophyly of Aneides was only weakly supported in some analyses and there is no evidence for the monophyly of Plethodon or of the western species of Plethodon. Excluding the relatively distant outgroup, down-weighting saturated substitutions, and analyzing conserved data partitions did not yield additional resolution or support among the lineages of western Plethodon and Aneides. These results are consistent either with saturation of sequences, due to the age of the lineages, or with relatively rapid radiation. An old, rapid radiation is consistent with the results of previous studies. An analysis of current taxonomy within the phylogenetic framework presented here retains [the genus] Aneides and recognizes [the genus] Plethodon as a metataxon (indicated with an asterisk, Plethodon *). CNAH Note: Western North American members of the genus Plethodon should be placed in a distinct genus; temporary categories such as "metataxon" have not been adopted by the herpetological community. Because Plethodon has now become an unwieldy and evolutionarily uninformative genus of over 50 species of salamanders, work is in progress to provide a distinct genus for the western species in order to clarify the relationships of these amphibians by means of a useful taxonomy. Wiens et al. (2006. Evolution 60(12): 2585–2603) provided yet more evidence that the western members of the genus Plethodon should be placed in a distinct genus. As noted above, work on doing this is in progress; for those that use a traditional binomial classification, keeping the distinct western Plethodon clade hidden in a transcontinental North American genus containing over 50 species is uninformative for most of the herpetological (and biological) community.