Meeting Abstract
Climate change is radically transforming the thermal quality of global habitats. Changes in ambient temperature due to anthropogenic climate change portend to alter species activity patterns, raise field-active body temperatures, and modify their performance capacities. Whereas species have already altered their distributions or phenology to cope with changing environments, the evidence for physiological traits evolving in response to rising temperatures is limited. When organisms specialized to narrow thermal niches prefer and are active at body temperatures close to their upper thresholds for activity and function, shifts in the operative temperature distribution of thermal environments may result in a severe reduction in performance capacity. As a result, natural selection in altered thermal environments should be strong. However, many models have suggested the likelihood of thermal adaptation is low, because of limited variation among individuals. Here, we estimate the strength and form of natural selection on major thermal traits linked with the ability of organisms to exploit environments exceeding their physiological limits. We detected significant directional selection favoring lizards with warmer thermal preferences and greater sprint performance at their optimal temperature. Our analyses also revealed convex correlational selection between thermal preference and critical thermal maxima. Assuming thermal traits are heritable, we conclude evolutionary adaptation may be a viable mechanism of long-term persistence in altered thermal environments.
