Assessment of Allelic Variation Among Massasauga Rattlesnake Populations via Microsatellite Analysis

Abstract

The decline in populations of the eastern massasauga rattlesnake (Sistrurus catenatus catenatus) across its range is of concern to conservation managers and the species is currently a candidate for federal listing. Because only four eastern massasauga populations are known to occur in Missouri, the species is on the Missouri Endangered Species List. We sought to produce a molecular genetic data set that could be used to inform conservation management decisions about three of these populations. Our method was to collect and analyze data from three microsatellites sites in an effort to provide insight into the genetic health of the populations and into relationships between them. Our method was controlled by inclusion of two populations of the western massasauga (Sistrurus catenatus tergeminus) from southeastern Nebraska. The final data set included 111 individuals from Missouri and Nebraska populations. Although a significant portion (92%) of alleles were shared between each population, low levels of heterozygosity were detected, indicating local inbreeding. Tests of population differentiation suggested that little to no gene flow between these populations has occurred, giving rise to unique allele frequencies and combinations which may be of high conservation value. Most notably, significant differentiation was observed between putative subpopulations at the Squaw Creek National Wildlife Refuge that are in close proximity to one another. Our results illustrate the value of molecular genetics analysis in conservation management and have important implications for the management of Missouri massasauga populations.