Schimmel/Conrades Science Center 163

“Context-Dependent Coevolution of Rattlesnakes and Ground Squirrels”

Predators and prey coevolve to produce some of the most extreme and fascinating characteristics of animals, but coevolution is not a simple race to the top. The occurrence, strength, and outcomes of coevolution are hypothesized to be determined by multiple factors, some environmental and others intrinsic to the species involved. We have assessed the role of three of these contextual factors on coevolving rattlesnake venom and squirrel venom resistance: mechanisms of interaction, population demography, and trait complexity. Sampling venom from different populations in California where California ground squirrels have evolved resistance to the venom of northern Pacific rattlesnakes, I developed methods to test for population-level adaptation in these traits. We used these samples to test for local adaptation in a snake-prey relationship for the first time, where venom enzymes have evolved to overcome resistance. It appears that venom and venom-resistance are not part of an arms race, but rather a matching-based interaction akin to molecular locks-and-keys between multiple venom proteins and inhibitor molecules. Finally, next generation DNA sequencing data has provided insight into demographic factors that give rattlesnakes and evolutionary edge over their prey. The discoveries made in these rattlesnakes and ground squirrels help us better understand how context in the coevolutionary process produces nature’s astonishing diversity of species and their traits.

Matthew Holding is a Ph.D. student in the Gibbs Lab of the Department of Evolution, Ecology, and Organismal Biology at The Ohio State University.