Genetic identity of endangered massasauga rattlesnakes (Sistrurus sp.) in Missouri

Abstract

An important application of DNA-based genetic techniques in conservation genetics is to establish the taxonomic identity of individuals whose ancestry is uncertain, especially those from declining populations. Massasauga rattlesnakes (Sistrurus catenatus) in Missouri currently persist in three isolated populations and have been classified as eastern massasauga rattlesnakes (S. c. catenatus), which is a candidate for listing as a Federally Threatened or Endangered species. However, previous morphological evidence has suggested that these snakes are either hybrids between the eastern massasauga (S. c. catenatus) and the non-threatened western massasauga (S. c. tergeminus) or are pure S. c. tergeminus. Here, we analyze microsatellite DNA and mtDNA variation to assess the taxonomic identity of individuals from two of the three populations specifically those found in Holt and Linn Counties, Missouri. Population and phylogenetic analyses strongly support the conclusion that snakes in both populations are genetically most similar to reference S. c. tergeminus individuals from Kansas and are not related to S. c. catenatus individuals from Illinois and Ohio. These results argue that the current classification of these snakes as endangered S. c. catenatus is unwarranted and hence that the overall range-wide numbers of S. c. catenatus are less than previously estimated. Nonetheless the Missouri populations, while not part of the federally listed taxon, are strongly deserving of protected status at the state level because of their rarity within the state.