Analysis of the Contact Zone between the Dusky Salamanders Desmognathus fuscus fuscus and Desmognathus fuscus conanti(Caudata: Plethodontidae)

Abstract

Two most widely distributed “subspecies” of the Desmognathus fuscus complex are the northern dusky salamander (Desmognathus fuscus fuscus) and the spotted dusky salamander (Desmognathus fuscus conanti). Previous mitochondrial DNA and allozyme studies of this complex have suggested that these two forms should be granted species-level recognition. However, detailed examination of populations inhabiting the region where the two taxa come into contact have not been performed to corroborate this taxonomic change. In this study, specimens were collected from four transects that traverse the putative contact zone. Allozyme and color pattern analysis were employed to determine the nature of variation across the area and evaluate the taxonomic status of D. f. conanti. Phylogenetic analyses of allozyme data divide the populations sampled into at least four major groups, two of which are referable to Desmognathus fuscus (groups A and C) and two referable to D. conanti (groups B and D). This study supports the distinctiveness of D. conanti by revealing parapatry between populations of groups A and B in western Kentucky with only a minor amount of hybridization between them and identifies color pattern differences that are effective for characterizing most group B individuals. The data presented here suggest that a longitudinal division may exist within D. conanti in central Alabama. Group C occurs primarily on the Piedmont of North Carolina and Virginia and appears to hybridize with group A in central Virginia. Groups C and D are treated, conservatively, as D. fuscus and D. conanti, respectively; but further study may reveal that each is a distinct species.