Population variation in escape behavior and limb morphology of collared lizards (Crotaphytus collaris) in Oklahoma

The evolution of the morphological traits underlying locomotor performance is often addressed at the level of species comparisons; however, examining variation in traits within a species and the underlying selective pressures that presumably mold those traits can offer great insight into the effects of natural selection, as well as the selective forces responsible for phenotypic changes. We studied limb morphology and escape behavior of three Oklahoma populations of collared lizards: Glass Mountains (GM), Sooner Lake (SL), and Wichita Mountains (WM). Predation differs among populations, with WM > SL >> GM. Habitat openness also varies, with SL > GM > WM. Our analysis of limb morphometrics revealed that WM had the longest hindlimb elements, GM lizards had the shortest, and SL lizards were intermediate. These differences are consistent with the hypothesis that predation pressure rather than habitat structure is most important in determining hindlimb morphology. WM lizards were found to have the longest approach distance among populations, but GM lizards ran the longest distances from predators. These differences in escape behavior support the hypothesis that predation pressure is important in determining population differences in behavior.