WINNE, Christopher T; FEDEWA, Luke A; HOPKINS, William A; University of Georgia’s Savannah River Ecology Laboratory: Thermal Sensitivity of Swimming Performance in Neonate Black Swamp Snakes, Seminatrix pygaea paludis

Understanding the relationship between maximum performance and performance breadth is a central issue in understanding the evolution of thermal performance in ectotherms. In evolutionary biology, organisms are often assumed to follow the principle of allocation in which there is a tradeoff between maximum performance and performance breadth, and the presence or absence of such a tradeoff in thermal physiology has been demonstrated (using models) to affect the tempo of evolutionary changes to changing environmental temperatures. Currently our understanding of performance tradeoffs is primarily limited to a few quantitative genetic studies of invertebrate organisms and laboratory studies on bacterial evolution. The few studies that have focused on such tradeoffs in vertebrate organisms generally have been studies of phenotypic tradeoffs among closely related species. In this study, we measured the thermal dependence of maximum swimming velocity in 79 neonate black swamp snakes (Seminatrix pygaea paludis), from 14 litters born in a common garden environment. All snakes were raced twice down a 3m racetrack at 6 temperatures (10, 15, 20, 25, 30, and 35C). We estimated broad sense heritabilities for performance breadth and maximum performance, as well as analyzed our data to determine whether or not there is a genetic or phenotypic tradeoff between maximum performance and performance breadth.