Genetic structure of winter populations of the endangered Indiana bat (Myotis sodalis) prior to the white nose syndrome epidemic: implications for the risk of disease spread

The spread of white nose syndrome raises serious concerns about the long-term viability of affected bat species. Here we examine the geographic distribution of genetic variation, levels of population connectivity that may influence the spatial spread of WNS, and the likelihood that recent population declines in regions affected by WNS have led to the loss of unique genetic variation for the endangered Indiana bat (Myotis sodalis). We amplified a fragment of the mitochondrial control region for 375 individuals and genotyped 445 individuals at 10 microsatellite loci from 18 sampling sites distributed across the majority of the species’ range. Analysis of mitochondrial DNA indicated the presence of at least five distinct matrilineal clusters, with the most pronounced differences between northeastern sites and those in the rest of the range. The majority of individuals in the Ozark-Central, Midwest, and Appalachian recovery units fell into a single cluster. Significant differentiation also was observed between one Appalachian and one Midwestern site and the majority of other sites. However, using nuclear microsatellites we observed the absence of differentiation and widespread gene flow among all hibernacula, suggesting the occurrence of extensive gene flow through dispersal and mating. The absence of genetically distinct populations within the range of Indiana bats indicates a lack of barriers to WNS transmission, and it is unlikely that significant portions of the hibernating population of Indiana bats will remain disease free into the future. Further, while matrilineal gene flow was restricted among some sites and regions, we found no genetic evidence to support the division of Indiana bats into separate recovery units.