Midwest Fish & Wildlife Conference 2016

AUTHORS: Michael G Sovic, The Ohio State University; Anthony C Fries, The Ohio State University; H. Lisle Gibbs, The Ohio State University

ABSTRACT: Identifying phylogenetically-distinct lineages and understanding their origin can help identify conservation units in endangered species. Such analyses are being transformed by the availability of genomic-scale datasets and novel analytical approaches that allow statistical comparisons of different historical scenarios as causes of phylogeographic patterns. Here, we use genomic-scale RADseq data to identify phylogenetically-distinct lineages representing potential conservation units in the rare eastern massasauga rattlesnake Sistrurus catenatus. We then apply coalescent-based modeling techniques to identify the evolutionary mechanisms responsible for the origin of such lineages. We find no evidence for distinct lineages across the species range east of the Mississippi River, suggesting that S. catenatus in this region represent a single conservation unit. We also identify a previously unrecognized lineage on the western edge of the range of this snake represented by three populations in Iowa. Individuals in these populations consist of genetic admixtures containing ~25% genetic contribution from a nearby non-threatened sister species S. tergeminus. Tests of historical demographic models support the hypothesis that the genetic distinctiveness of Iowa snakes is due to a combination of isolation and historical introgression between S. catenatus and S. tergeminus. Our work provides an example of how model-based analysis of genomic-scale data can inform the identification and classification of conservation units in species of conservation concern.