Graduate Research for Mason Murphy: Dispersal congruency and population structure within an imperiled host-parasite system

Freshwater mussels (order Unionoida) are one of the most threatened groups of taxa both within the United States and worldwide. Freshwater mussels exhibit a distinctive lifestyle, in which they disperse via fish hosts as larvae. Although the causes for freshwater mussel declines are numerous1, the requirement of a fish host for larval development and dispersal has direct implications for mussel conservation2. First, host abundance can influence the abundance of a mussel species at a particular location3, and this is expected to have an influence on the maintenance of genetic diversity in populations, with smaller mussel populations having a greater risk of population genetic bottlenecks. Second, the degree of host specialization and the geographic distribution of a host can influence the geographic distribution of mussel species4, with mussel species that have the smallest distribution having the greatest risk of extinction. Third, dependence on a host for dispersal directly ties dispersal and gene flow of mussel species to that of its host, and the geographic, ecological, and environmental factors that influence gene flow among host populations are expected to influence gene flow among mussel populations5. Dispersal is fundamental in facilitating gene flow and distributing genetic variation among populations. Furthermore, limited gene flow can lead to inbreeding depression or local extinction6. Few investigations have assessed the role of host dispersal as it relates to mussel population decline, yet long-term population viability is not only dependent on local survival and recruitment, but also on host population sizes and host dispersal. Here, I propose an integrative set of objectives focusing on mussels and their hosts by employing powerful population genetic data aimed to aid in the conservation of freshwater mussel populations.