The dusky salamander genus Desmognathus is a species-rich group of amphibians distributed across eastern North America. Although many species occupy deciduous forest streams, the group demonstrates remarkable ecological breadth, ranging in habitats from spruce forests to coastal swamps. Despite their ecological diversity, the species of dusky salamanders are quite similar in appearance and all share a pattern of brown, mottled markings that makes species identification notoriously difficult. As a result, interpretations regarding the exact number of species (and relationships among them) remain controversial and problematic. This study will work to resolve evolutionary relationships of dusky salamanders by: 1) sampling salamanders on a very fine geographic scale, and 2) assessing variation among these sampled populations using molecular characters (DNA sequences for several genes) as opposed to morphological characters. Preliminary results confirm the validity of certain species but also have revealed additional, undescribed species. Moreover, preliminary work using a new geometric approach to morphological analysis suggests that subtle variation in head shape may play an important role in the group's observed ecological diversity by allowing various species of dusky salamanders to forage in slightly different ways.
This study will generate a large database including several thousand specimens (to be deposited in the Field Museum of Natural History, Chicago) and DNA sequences (to be deposited in Genbank), which will be available to biologists worldwide. The fine-scale sampling will help to identify all species in the group and delimit their geographic distributions, findings important to conservation and land management.
