Collaborative Research: Genome-Scale Phylogeographic Analysis of Desmognathus Salamanders

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The Dusky Salamanders, genus Desmognathus, are one of the most diverse and abundant animals in the eastern forests of the United States. They are classic study organisms for ecology and behavior. Along with frogs and other salamanders worldwide, they are also disappearing at an alarming rate, possibly due to factors such as habitat loss, infectious diseases, and other environmental stresses. Despite their visibility and imperilment, we know little about their genetic diversity and evolutionary history. While there are only 21 currently named species, recent work using DNA sequencing has revealed at least 45 potential species, which would more than double the size of the group. This research will reveal the true diversity of the group, providing a future platform for ecological and evolutionary studies of Desmognathus, and guiding conservation-management decisions for this imperiled group of aquatic vertebrates. Broader impacts will include a K-12 teaching module for understanding forest ecology, centered on salamanders, and updated species accounts for local wildlife-management authorities. This will be invaluable for understanding the biodiversity heritage of the United States.With an exhaustive "ecodrainage" sampling technique, this research will analyze 7,000 samples from nearly every known Desmognathus population. The study will use next-generation genomic sequencing of DNA to understand the true genetic diversity of the group. These data will allow researchers to understand the evolutionary history of divergence, hybridization, and species boundaries from a genetic perspective, using modern species-delimitation methods. Many species are also difficult to distinguish by eye. Thus, this research will complement the genetic perspective with 3-dimensional geometric morphometric analyses of size and shape, to reveal the subtle but significant morphological differences between populations. Overall, this research will generate a robust and fully-sampled estimate of the true number of Desmognathus species, their morphological variation for identifying them in the field, and their geographic range. This research will likely yield an increased number of Desmognathus species, while also showing a complex history of introgression, hybridization, and incomplete ecological speciation in the group.