The Population, Evolutionary and Conservation Genetics of the Eastern Massasauga Rattlesnake (Sistrurus catenatus catenatus)

Abstract

<p>This thesis assesses two distinct aspects of the genetics of the eastern massasauga rattlesnake ( Sistrurus catenatus catenatus). Firstly, work relating to the population and evolutionary genetics of the eastern massasauga rattlesnake, and the conservation implications of the results are presented. In this study, variation at a portion of mitochondrial DNA (mtDNA) and at two nuclear intron DNA loci was examined for snakes from various populations, in order to examine the partitioning of genetic diversity among populations. Seven mtDNA haplotypes were identified, most found in one or two U.S. populations of snakes. Intron variation was low and phylogenetically uniformative. Neither mitochondrial nor nuclear DNA showed any phylogenetic structuring. Results also suggest that eastern massasauga rattlesnakes have undergone a post-Pleistocene population expansion from a glacial refugium. From a conservation perspective, three geographical groupings of populations that showed significant genetic differentiation were identified, suggesting that these groups should be managed independently, in order to conserve within-species variation. Secondly, the concerted evolution of two control-region-like sequences in eastern massasauga mitochondria is discussed. In this study, two entire control-region- like sequences were sequenced in 10 ea tern massasauga rattlesnakes, one found in the cytb-12S rRNA region, and the other in the IQM tRN cluster as well as the tRNA sequences flanking these regions. Also the sequence of the last half of both control regions for 28 individual snakes was compared. Both control regions were found to have a divergence of less than 0.5% within individuals. Among the 28 individuals only three showed different sequences between the two control regions, and these sequences differed at only one nucleotide. The similarity of these separate regions within individuals could be attributed to concerted evolution, potentially due to gene conversion. A minimum gene conversion rate of one conversion per 1.2 million years is estimated for the sequences.</p>