20.3 Saturday, Jan. 4 14:00 Behavior simultaneously drives and impedes evolution: An empirical test using the tropical lizard, Anolis cybotes MUñOZ, M.M.*; LOSOS, J.B.; Harvard University; Harvard University email@example.com
Behavior determines how organisms interact with their environment and has long been posited as a pacemaker for evolutionary diversification. The classical view is that novel behaviors expose organisms to new selective pressures, in turn “driving” morphological and physiological evolution. Behavior can also restrain evolutionary change. The “behavioral inhibition” hypothesis suggests that some behaviors, such as thermoregulation, help organisms maintain a constant selective environment, obviating the need to adapt even in the face of changing environments. However, behavioral drive and inhibition are not necessarily mutually exclusive processes – in response to a changing environment, behavioral changes that keep a population in its ancestral niche with regard to one niche axis often will be accomplished by subjecting the population to novel selective pressures on a different niche axis. In this study we test the hypothesis that behavior simultaneously inhibits physiological evolution while impelling morphological evolution in the lizard, Anolis cybotes, a species that ranges from sea level to nearly 3000 meters on the Caribbean island of Hispaniola. We demonstrate that behavioral flexibility allows individuals to maintain a constant body temperature along two elevational transects, thus precluding the evolution of differences in thermal physiology (behavioral inhibition). We show that the behavioral change allowing lizards to maintain a constant body temperature is accomplished by altering the part of the environment they occupy, and test whether a shift in structural habitat use in turn impels morphological evolution (behavioral drive). We discuss the implications of our findings in the light of contemporary debates in evolutionary biology.