The individuals constituting a species frequently differ in appearance from one locality to another, but the processes which result in this variation are often difficult to recognize. Processes producing such geographic differentiation include chance events brought about by isolation or adaptation to local conditions. Countering these processes is gene flow, the transfer of genetic material from one location to another (e.g., via the movement of individuals). Unfortunately, few examples exist where the interplay among such processes is clearly understood. Island and mainland populations of snakes in western Lake Erie provide a situation where the importance of gene flow can be studied with relative ease. These populations are unusual because of the large amount of color pattern variation they exhibit. Alternative explanations for this variation differ in the amount of gene flow they require. This project aims to measure rates of gene flow among island and mainland snake populations using gel electrophoresis, a technique which makes use of genetically based differences in protein structure to characterize variation within and among populations. Coupled with information on local adaptation and on the geological history of the region, this project will provide an unusually detailed picture of the processes giving rise to geographic variation.
