MAHONEY, M .J.; Museum of Vertebrate Zoology, UC Berkeley: Phylogeny and demographic history of the Plethodon elongatus species group (Caudata: Plethodontidae)

Plethodon elongatus and P. stormi are closely related salamander species with narrow distributions in northwestern California and southwestern Oregon. I used mitochondrial sequence data to examine biogeographic hypotheses concerning the divergence and regional history of these two species. I sampled populations throughout the range of both species and sequenced over 1700 bp from three mitochondrial protein-coding genes (cytochrome b, NADH dehydrogenase subunit 4, and ATPase 6). Four haplotype groups with non-overlapping geographic ranges were recovered in separate and combined analyses of the genetic data. Relationships among the main haplotype groups are not strongly supported in all analyses, however P. elongatus and P. stormi are recovered as monophyletic sister taxa in the combined ML and MP analyses. Mismatch distributions and Tajima�s D statistic indicate that one haplotype group went through an expansion and now occupies the northern two thirds of the range of P. elongatus. The P. elongatus haplotype group from the southern third of the range and the P. stormi haplotype group appear to have been more stable over time. The mitochondrial boundary between P. elongatus and P. stormi is congruent with morphological and allozyme data and continued treatment as sister species is supported. Broadscale patterns of morphological and allozyme variation within P. elongatus are not concordant with the mitochondrial groups recovered in this study. However, fine scale examination of mtDNA and morphology at the boundaries between haplotype groups may give additional insight into the history of this species.