SICB 2015: Thermal Biology and Gene Flow in Bahamian Anolis sagrei

Anolis sagrei. Photo from Wild about Spain

An important problem in climate change biology is understanding how evolutionary dynamics will influence the ability of populations or species to persist as environmental conditions change. In general, there are three ways that such evolutionary change can occur: (1) novel beneficial mutations can arise de novo; (2) rare alleles within a population can become beneficial and sweep to fixation; or (3) gene flow between locally adapted populations can introduce beneficial alleles to populations that did not previously have them. The potential for this latter scenario was investigated by Mike Logan using A. sagrei on a system of cays off of the Bahamian island Exuma. Mike measured operative thermal environments on the cays and Exuma, as well as temperature-dependent physiology of the animals in each population. He found that the islands differed in mean temperature and variability, and that optimal temperatures for physiological performance correlated with mean island temperature. Next, Mike used genetic markers to estimate population structure and rates of migration between the keys and the mainland. He found evidence for extensive gene flow between the populations, but with an interesting twist: gene flow was highest between populations that had the most similar thermal environments. Within the context of climate change, the observation of gene flow among islands based on thermal conditions suggest that as conditions change across a species’ range, beneficial alleles may be able to move into the populations where they are needed most. Mike’s work adds an important piece to an emerging picture about the interplay between standing genetic variation, local adaptation, and responses to global change.

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