Meeting Abstract
Phenotypic evolution is often rapid on islands, resulting in numerous, ecologically diverse species. Although adaptive radiation proceeds along various phenotypic axes, the island effect of faster evolution has been mostly tested with regards to morphology. Here, we leverage the physiological diversity and species richness of Anolis lizards to examine the evolutionary dynamics of three key traits: heat tolerance, body temperature, and cold tolerance. Far from an island effect, we discovered faster heat tolerance evolution in mainland lineages. Island and mainland anoles evolve toward distinct trait optima, with island taxa being more warm-adapted. Higher optima and slower evolution are consistent with the Bogert Effect, or evolutionary inertia due to behavioral buffering. Correspondingly, island lizards thermoregulate more than mainland species, despite occurring in similar thermal environments. Lower physiological limits, in contrast, cannot be behaviorally buffered against selection and, not surprisingly, cold tolerance evolution did not differ between habitats. Given ecological release from competitors and predators, the costs of thermoregulation may be lower on islands. As a corollary, ecological opportunity on islands may actually slow, rather than accelerate, evolution. Our results emphasize that physiological diversification is a key feature of adaptive radiation, and that behavior can illuminate the numerous interactions shaping its evolution.
