Paul Hime: Leveraging genomics to understand and conserve the critically endangered Ozark hellbender salamander

Hellbender salamanders (Cryptobranchus alleganiensis) are large, obligately aquatic salamanders that were once widespread and abundant in streams and rivers across the eastern and central United States. These long-lived salamanders are restricted to cold, highly oxygenated aquatic habitats and serve as key predators in riverine ecosystems. Hellbender populations have been rapidly declining throughout their historical distribution over the past forty years due to the combined effects of habitat degradation and fragmentation, pollution of aquatic ecosystems, emerging infectious diseases, and poaching. Many populations are completely extirpated and those that remain are increasingly fragmented, elevating the risk of local and global extinction. Cryptobranchus is listed by the IUCN as Near Threatened and populations in the Ozark Mountains were recently listed as Federally Endangered by U.S. Fish and Wildlife Service. Recent conservation efforts have sought to curb these precipitous declines by identifying and protecting remaining populations, by bolstering declining populations with captive bred individuals, and by reintroducing hellbenders into extirpated areas. Despite these efforts, several impediments must still be surmounted in order to protect this ecologically important salamander from impending extinction. Although hellbenders are currently classified as a single species with two recognized subspecies (C. a. alleganiensis in the Appalachians and C. a. bishopi in the Ozark highlands), emerging genetic research suggests that this genus may comprise several cryptic species, each substantially smaller and more imperiled than previously realized. The current lack of understanding of species boundaries in this group prevents comprehensive conservation management. Furthermore, effective conservation efforts with Cryptobranchus require detailed knowledge of the demographic and population genetic parameters of distinct lineages, such as rates and patterns of migration and gene flow, effective population sizes, levels of genetic diversity, and the extent of adaptive differences between populations. Here I propose an in-depth population genetic and phylogenetic analysis of hellbenders from across the Ozark highlands of Missouri and Arkansas, including sampling from all river systems where this species occurs in the western portion of its range. This project is aimed at resolving the evolutionary relationships among these most imperiled hellbender populations by leveraging emerging techniques for genome-wide DNA sequencing to delimit cryptic species boundaries and to detect patterns of local adaptation. This work comprises fits within the broader context of my thesis work at University of Kentucky which seeks to understand the ways in which changes in the genomes of organisms drive and reflect the divergence between lineages. At a basic level, this research seeks to shed light on the evolutionary forces which drive divergence during the earliest stages of speciation. At a more applied level, insights from this work will inform conservation management decisions in terms of captive breeding and repatriation efforts.