HUSAK, Jerry F.*; LOVERN, Matthew B.; Virginia Tech; Oklahoma State University: Sexual selection on whole-animal performance: lizard locomotion and mating success

Studies of sexual selection have focused mainly on morphological and behavioral traits, whereas studies of the evolution of physiological and morphological traits have focused on selection acting on whole-animal performance. Most of these studies of performance evolution have focused on the role of natural selection via differential survival, but the general approach of examining whole-animal performance as the trait directly under selection (instead of morphological traits) may be applied to studies of sexual selection. We investigated the potential for sexual selection on sprint speed performance in collared lizards (Crotaphytus collaris), considering the influence of circulating hormone levels as possible alternative targets of sexual selection. Among territorial, adult male collared lizards, only sprint speed significantly predicted territory area and number of offspring sired as determined by genetic paternity analysis, whereas body size, head size, and hindlimb size did not. Neither testosterone nor corticosterone levels correlated with sprint speed, territory area, or number of offspring sired. Thus, our results provide a direct link between whole-animal performance and mating success, suggesting that intra-sexual selection acts directly on sprint speed performance and drives the evolution of underlying morphological traits. Behavioral traits contributing to mating success likely interact with, or are constrained by, whole-animal performance, leading to variation in mating success within a population.