Conservation Genetics, Captive Breeding and Management of the Eastern Massasauga Rattlesnake
 Massasauga Rattlesnakes (Sistrurus catenatus) |
 Kirtlands snake (Clonophis kirtlandii) |
As a sub-discipline within conservation biology, conservation genetics is the application of population and quantitative genetic principles to biodiversity management and protection. Of particular concern for threatened and endangered species are losses of genetic variation that may trigger population declines through inbreeding depression or prevent adaptive responses to changing environmental conditions. Thus, genetic analyses are rapidly becoming part of the standard toolkit of conservation biologists. One outgrowth has been a better appreciation of the need to incorporate genetic information into captive breeding programs. As part of a larger investigation of landscape-level patterns of genetic variation in the Great Lakes region of North American (Robinson, MS thesis, 2005, Placyk et al. 2007), masters student Jesse Ray, Dr. Mel Duvall, and I have recently completed an analysis of mitochondrial DNA sequence variation of 136 captive and wild Eastern Massasauga Rattlesnakes with the goal of guiding management of wild populations and informing a captive breeding program being undertaken by the Association of Zoos and Aquariums (AZA) as a part of its Species Survival Plan (SSP) for this snake. Once abundant, this snake now persists in isolated patches; is listed as endangered, threatened, or of special concern in each state or province in which it occurs; and is a candidate for federal protection. Our genetic analyses revealed three moderately differentiated groups of individuals corresponding to three separate geographic subunits. One subunit includes snakes from Iowa, Illinois and Wisconsin; the second subunit includes snakes from Indiana, Ohio, southern and central Michigan, and southwestern Ontario; and the third subunit includes snakes from Pennsylvania, New York, northern Michigan, and other parts of Ontario. This pattern is consistent with a northeastward range expansion of Eastern Massasauga Rattlesnakes from unglaciated areas into formerly glaciated parts ca. 10,000 years ago. However, whether colonization followed a clockwise route from northern Michigan through Ontario and into New York and Pennsylvania or a counterclockwise route from Pennsylvania and New York through Ontario and into northern Michigan remains unresolved. On a more practical level, our results suggest that the AZA should strive to maintain these subunits as distinct in their captive breeding program. To accomplish this, the AZA has proposed augmenting the captive population with additional wild-caught animals from underrepresented areas. To further guide the management of this and other Midwestern snake species, we are using a Geographic Information Systems (GIS) approach to identify climatic variables most strongly associated that the current distribution of a species and to project how species distributions may change in response to global climate change over the next 50 years. Such information can be used to help position preserves and habitat corridors necessary for species persistence.