Range-wide phylogeography of Chamberlain's dwarf salamander (Eurycea chamberlaini)

In the southeastern United States, the diversity of lungless salamanders (family Plethodontidae) in the Piedmont and Coastal Plains is often overshadowed by that of the Appalachian highlands. However, recent systematic studies have uncovered previously undescribed diversity in these lowlands, and here, we contribute to this body of work by reexamining the phylogeography of the Chamberlain's dwarf salamander (Eurycea chamberlaini)---a small, biphasic salamander with an unusual and disjunct distribution throughout the Carolinas. We collected hundreds of samples through range-wide geographic surveys, generated genome-wide SNP data from 2RAD libraries, and conducted a series of complementary phylogenetic, population genetic, and species delimitation analyses. Our fieldwork revealed this species to be widespread and common even in relatively disturbed habitats, and we found no evidence for the evolutionary distinctiveness of disjunct populations in and near the Appalachian foothills. Instead, we found that populations in the southwestern Atlantic Coastal Plain of South Carolina were sister to all other populations of E. chamberlaini, showing marked genetic differentiation with little evidence of gene flow. We describe other geographic patterns in genetic differentiation and diversity of E. chamberlaini and highlight opportunities for future research to resolve remaining questions about species boundaries in the group.