Systematics of dusky salamanders, Desmognathus (Caudata: Plethodontidae), in the mountain and Piedmont regions of Virginia and North Carolina, USA

Abstract

We analysed mitochondrial (cytochrome b) nucleotide sequences, nuclear allozyme markers, and morphometric characters to investigate species boundaries and phylogenetic relationships among dusky salamanders (Desmognathus) in the southern Blue Ridge and adjacent Piedmont Physiographic Provinces of Virginia and North Carolina. Our results revealed four distinct mitochondrial DNA clades that are also characterized by distinct allozyme markers. One clade consists of sequences derived from populations distributed from New England to south-western Virginia that are referable to Desmognathus fuscus Rafinesque, 1820, although there is considerable sequence and allozyme divergence within this clade. A second clade consists of sequences derived from populations referable to Desmognathus planiceps Newman, 1955, a form that we resurrect from its long synonymy under D. fuscus. Desmognathus planiceps and D. fuscus also differ in mandibular tooth shape. Two other cytochrome b sequences recovered from populations along the Blue Ridge escarpment in southern Virginia are quite divergent from those of the previous two clades, and these populations may represent yet another distinct species. Sequences from a population in the Brushy Mountains in the Piedmont of northern North Carolina are similar to those of Desmognathus carolinensis. Population groupings indicated by allozyme data generally correspond to the cytochrome b clades. Cryptic diversity in Appalachian desmognathan salamanders clearly requires further study. © 2008 The Linnean Society of London, Zoological Journal of the Linnean Society, 2008, 152, 115‐130. ADDITIONAL KEYWORDS: allozymes ‐ cytochrome b ‐ Desmognathus planiceps ‐ mitochondrial DNA ‐ morphometrics ‐ phylogeography ‐ taxonomy.