EAGER: Evolutionary mechanisms and repeatability of adaptive evolution in urban heat islands

Predicting the responses of living systems to ecosystem alteration requires a framework for understanding the pace and pattern of evolutionary change. Because of urbanization, cities now host the majority of the human population. As a result, more wildlife must contend with the novel and extreme environments posed by urban landscapes.

A major consequence of urbanization is ecological homogenization, wherein urban environments across the globe are more similar to each other than they are to adjacent undisturbed surroundings. This environmental similarity begs the question: Do species that successfully colonize cities follow predictable evolutionary paths to success? This study examines evolutionary mechanisms involved in adaptation to urban heat islands using a widespread lizard species (Anolis cristatellus) that has independently colonized several cities across Puerto Rico.

This research will detail the extent to which urban populations display greater heat tolerance than their forest counterparts. The study will measure diverse performance traits over a range of temperatures. Those data will be used to identify groups of genes involved in thermal acclimation that display elevated divergence within each urban-forest pair.

Additionally, an audio documentary series for the general public will be produced which focuses on the various ways human activity shapes the biology of nonhuman species. This high risk-high reward research exploits a novel methodology that could greatly advance our understanding of the genetics underlying thermal physiology and adaptation on anthropogenic time scales.

Preliminary data show that three of these colonization events are associated with signatures of selection at the organismal, regulatory, and genetic levels. This suggests candidate mechanisms that drive parallel selection in urban environments. The research will integrate population and physiological genomics to identify the genetic basis of thermo-hydric phenotypes important for adaptation to urban heat islands.

This study will integrate several modern physiological approaches into a single experimental design. The plan is to conduct simultaneous high-throughput quantification of thermal performance curves across 21 subordinate traits associated with metabolic, respiratory and pulmonary physiology. These populations will then be examined for patterns of allele specific expression to identify evolutionary mechanisms of repeated adaptive regulatory evolution.

Comparing divergent physiology, gene expression, genetic variation, and the mechanisms by which they have evolved across the three focal population pairs will provide unprecedented insights into adaptive physiological evolution in the face of anthropogenic habitat alteration. The mechanisms driving local adaptation and plasticity of thermal physiology are likely to play important roles in colonization of novel environments, adaptive divergence, and resilience to environmental perturbation.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.