Editorial Type:
Article Category: Research Article
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Online Publication Date: 01 May 2002

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

Page Range: 344 – 355
DOI: 10.1643/0045-8511(2002)002[0344:AOTCZB]2.0.CO;2
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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.

Copyright: The American Society of Ichthyologists and Herpetologists
 Fig. 1. 
 Fig. 1. 

Localities where Desmognathus (1–59 putative Desmognathus fuscus, 60 Desmognathus ochrophaeus) were collected for this study. Light dotted lines that connect some localities, represent original transects. Hatched lines follow the perimeter of the distribution of D. fuscus proposed by Petranka (1998). Inset map (upper left) is an enlargement of the squared region on the main map

 Fig. 2. 
 Fig. 2. 

Neighbor-joining tree, based on Cavalli-Sforza and Edwards (1967) chord distances. This tree demonstrates the separation of putative Desmognathus fuscus populations (1–59) into four disjunct groups (A and C, D. fuscus; B and D, Desmognathus conanti). Putative hybrid populations are indicated by * (A/C hybrids) or ** (A/B hybrids)

 Fig. 3. 
 Fig. 3. 

Parsimony tree based on allozyme data for 59 putative Desmognathus fuscus populations with Desmognathus ochrophaeus placed as an outgroup. Bootstrap analysis based on 1000 pseudoreplications generated bootstrap values (> 50%) for the major groupings that are reported adjacent to their corresponding node, and relative branch lengths are shown. This tree demonstrates the separation of putative D. fuscus populations (1–59) into four disjunct groups (A and C, D. fuscus; B and D, Desmognathus conanti). Putative hybrid populations are indicated by * (A/C hybrids) or ** (A/B hybrids)

 Fig. 4. 
 Fig. 4. 

Mapped representation of phylogenetic division of sampled populations into four groups (A–D) and putative hybrid populations

 Fig. 5. 
 Fig. 5. 

Inset map from Figure 1 demonstration the relatively discrete boundary between group A (open circles) and group B (filled circles) populations for the loci sAta-A, sIcdh-A, Ldh-A, and Ldh-B. Circles are proportionate to sample sizes (See Materials Examined).

 Fig. 6. 
 Fig. 6. 

Comparison of percent larval spot persistence (A) and postocular stripe coloration (B) for the size categories of groups A–C

Received: 19 Mar 2001
Accepted: 28 Nov 2001
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