Limited Gene Flow and Pronounced Population Genetic Structure of Eastern Massasauga (Sistrurus catenatus) in a Midwestern Prairie Remnant.

As anthropogenic changes continue to put ecological pressure on wildlife, obtaining measures of gene flow and genetic diversity are crucial for evaluating population trends and considering recovery strategies for small, isolated, and imperiled populations. We conducted a molecular assessment to expand on previous work to determine patterns of diversity and connectivity in the remaining disjunct Eastern Massasauga rattlesnake (Sistrurus catenatus) hibernacula in Illinois. We assayed 327 samples across 21 microsatellite loci for data collected from 1999-2015 in the Carlyle Lake region. We found hibernacula formed distinct genetic clusters corresponding to the three major study areas. Genetic structuring and low estimates of dispersal indicated connectivity among the major study areas is limited, and that each is demographically independent. Hibernacula exhibited moderate levels of heterozygosity (0.60-0.73), but estimates of effective population size (5.2-41.0) were low and comparable with long-term mark-recapture population size estimates. Our work suggests that recovery efforts should focus on managing the three major study areas as three separate conservation units to preserve and maintain the long-term adaptive potential of these populations. Specific management goals should include 1) maintaining or restoring connectivity among hibernacula, 2) protecting critical habitats such as crayfish burrows, and 3) minimizing all anthropogenic sources of mortality. Our molecular study provides additional details about demographic parameters and connectivity at Carlyle Lake to guide the recovery of Eastern Massasauga in Illinois and throughout its range.