Failed species, innominate forms, and the vain search for species limits: Cryptic diversity in dusky salamanders (Desmognathus) of eastern Tennessee

摘要

Cytochrome B sequences and allozymes reveal complex patterns of molecularvariation in dusky salamander (Desmognathus) populations in eastern Tennessee.One group of allozymically distinctive populations, which we refer to asthe Sinking Creek form (SCF), combines morphological attributes of Desmognathusfuscus with cytB sequences characteristic of Desmognathus carolinensis.This form is abruptly replaced by D. fuscus just north of Johnson City, TN withno evidence of either sympatry or gene exchange. To the south, allozymicmarkers indicate a broad zone of admixture with populations characterized bydistinct cytB sequences and that may or may not be ultimately referable to Desmognathusconanti. A third distinctive group of populations, which we refer toas the Lemon Gap form (LGF), occurs in the foothills of the Great Smoky andsouthern Bald Mountains and exchanges genes with Desmognathus santeetlahalong the escarpment of the Great Smokies, D. carolinensis in the southern BaldMountains, and populations of a different haplotype clade in the Ridge andValley. We treat all these as innominate forms that may represent ?failed species,?recognizing that it may never be possible to reconcile species limits withpatterns of phylogeny, morphology, and gene exchange in these salamanders.