Comprehensive Sampling Clarifies Phylogeography and Historical Biogeography of Slimy Salamanders West of the Mississippi River.

Accurate knowledge of species distributions is necessary for research and conservation. Slimy Salamanders (Plethodon glutinosus complex) are similar in appearance, tend toward small geographic ranges, and have a propensity for hybridization, necessitating genetic analysis and fine-scale sampling for accurate representation of species distributions. Our current understanding of the distributions of some Slimy Salamanders is based on coarse sampling. Several recent studies question the validity of some species, calling for more geographic and genetic sampling to confirm the species in this group and better define their distributions. Toward this, we analyzed the mitochondrial ND2 gene sequences of 434 individual Slimy Salamanders, 412 of which are from 294 localities west of the Mississippi River, USA. We also estimated ancestral ranges to better understand the biogeographic history underlying current species distributions. We found a much larger distribution for P. kiamichi than previously thought, including several contact zones with P. albagula. We confirmed the Ouachita River separates P. kisatchie and P. albagula in southern Arkansas. Texas P. albagula were not recovered as monophyletic, forming two distinct clades, one of which is nested within a large Interior Highlands (Ouachita and Ozark mountains) clade. Our data suggest P. sequoyah from the type locality have the introgressed mitochondria of P. albagula. We discovered three unnamed mitochondrial clades, one of which we hypothesize is nonintrogressed P. sequoyah. Our biogeographic analysis estimates multiple east–west dispersals across the Mississippi River and at least one west–east dispersal. With these findings, we have updated species distributions, identified contact zones and areas of potential contact, and revealed previously unknown evolutionary lineages. This information will be beneficial for further studies on this complex, which have thus far been hampered by unrefined species boundaries. Furthermore, this work has implications for revising the conservation ranks and management of western Slimy Salamanders. [ABSTRACT FROM AUTHOR]