Using microsatellite DNA to genetically identify a potential hybrid population of endangered massasauga rattlesnakes (Sistrurus catenatus) in north central Missouri

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The Ohio State University

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DNA-based genetic techniques can be used to identify individuals in wild populations whose ancestry is uncertain. The massasauga rattlesnake is a small rattlesnake found from central New York to southeastern Arizona. It is currently described as consisting of three subspecies: the eastern massasauga (Sistrurus catenatus catenatus), the western massasauga (Sistrurus c. tergeminus) and the desert massasauga (Sistrurus c. edwardsii). Due to morphological similarities between eastern and western massasaugas in north central Missouri (where the range of S. c. catenatus meets that of S. c. tergeminus), there is debate over the species identity of individuals in this population and the possibility that it is a hybrid population has been suggested. Here, I use microsatellite DNA from western and eastern massasaugas to determine the species identity of a central Missouri population. To do this, I used a combination of clustering analysis and distance-based phylogenetic analysis to determine the relationships among the western, eastern, and central Missouri populations. Cluster-based analysis using the program Structure showed that the central Missouri population clustered strongly with the western (tergeminus) populations. Distance-based phylogenetic analysis of populations also grouped the Missouri population with western populations and analysis of all individuals grouped the central Missouri individuals together with the western individuals. These results show that the western massasauga and central Missouri population are genetically similar, and both are highly differentiated from eastern massasauga populations. Therefore this data strongly suggests that the central Missouri population is Sistrurus c. tergeminus. This has the implications that one of the criteria for special protection status of this population has been removed and that the range of S. c. catenatus does not extend west of the Mississippi River which supports the possibility that the Mississippi River acts as a phylogeographical barrier for massasauga rattlesnakes.



hybrid rattlesnake, massasauga sistrurus catenatus, microsatellite DNA, tergeminus, endangered