KRENZ, J.G.*; HASELKORN, T.S.; BRODIE, E.D., III; BRODIE, E.D., JR.; JANZEN, F.J.: Molecular Phylogeography of Common Garter Snakes (Thamnophis sirtalis) in Western North America

Populations of the common garter snake (Thamnophis sirtalis) in western North America that are found in the same range as the coastally distributed rough-skinned newt (Taricha granulosa) display resistance to the poisonous effects of the newt’s tetrodotoxin (TTX), while common garter snake populations outside of the range of the newt do not display TTX resistance. In an effort to uncover the evolutionary pattern of TTX resistance in the common garter snake, we collected 2218 nucleotides of mitochondrial DNA sequence data including complete ND2, partial ND4, and partial cytochrome b gene sequences. Phylogenetic analysis of the data revealed at least two independent origins of TTX resistance in the common garter snake.