Molecular systematics of Plethodon and Aneides (Caudata : Plethodontidae :Plethodontini): Phylogenetic analysis of an old and rapid radiation

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 seque nced 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 eschscholt zii was used as the outgroup. Phylogenetic analyses using maximum-parsimony , neighbor-joining, and maximum-likelihood consistently recovered some rela tionships. The eastern species of Plethodon are a robust, well-supported cl ade. 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 Anei des were also consistently resolved with good support. The monophyly of Ane ides was only weakly supported in some analyses and there is no evidence fo r the monophyly of Plethodon or of the western species of Plethodon. Exclud ing the relatively distant outgroup, down-weighting saturated substitutions , and analyzing conserved data partitions did:not yield additional resoluti on or support among the lineages of western Plethodon and Aneides. These re sults 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 Aneides a nd recognizes Plethodon as a metataxon (indicated with an asterisk, Plethod on*). (C) 2001 Academic Press.