Rectifying Limitations On Species Delineation In Dusky Salamanders : Lineage Detection Using An Ecoregion-Drainage Sampling Regime

Abstract

The dusky salamanders (Desmognathus) constitute a large, species-rich group, and although a considerable body of literature exists on systematic relationships and adaptive trends, these issues have heretofore been approached in piecemeal fashion. Recent work has revealed Desmognathus to be far more lineage rich than previously imagined and demonstrated just how complex the taxon's evolutionary history has been. These recent advances underscore the need for additional sampling in areas and within lineages that have thus far been sparsely evaluated. I conceived and implemented a sampling regimen involving level IV ecoregion X independent river drainages designed for the comprehensive recovery of all genealogically exclusive lineages within the genus. I sampled over 550 populations across the range-wide distribution of described dusky salamander species and generated mtDNA sequence data for each population. A Bayesian phylogenetic reconstruction of the resulting haplotypes revealed forty-five independent evolutionary lineages, eleven of which have never been included in a comprehensive phylogenetic reconstruction and three of which have not been included in any molecular systematic survey. Although general limitations associated with mtDNA data preclude delineation of new species, I have redefined several species complexes and have also erected new informal species complexes. The dataset assembled here, which contains topotypic samples for all currently recognized species as well as most synonymies, should serve as a robust framework for future efforts to delimit species within Desmognathus.