evolutionary ecology | adaptation | global change biology
Using experimental islands to understand rapid adaptation
We have transplanted thousands of Anolis lizards to dozens of islands in the Panama Canal (photo, left) and The Bahamas (see the four pics below). Islands in both places differ in their biotic and abiotic environments such that populations are exposed to different agents of natural selection. We track these populations in real time with mark-recapture, and ask a diversity of questions about adaptation to novel environments.
The pictures to the left show four of our experimental islands in The Bahamas. In 2017 we transplanted populations of brown anoles (Anolis sagrei) to these islands. As you can see from the pics, they differ dramatically in habitat structure and substrate, and these translate into huge differences in thermal environments. We are studying how thermoregulatory behavior evolves on these islands, and whether changes in behavior result in subsequent physiological evolution. We are also investigating the genomic basis of adaptation to these different island environments.
Evolution in the face of gene flow
How do organisms adapt to local environments when they experience gene flow from other places? We are studying the Dominican anole (Anolis oculatus) to understand how populations can persist and even thrive in divergent environments while experiencing ongoing gene flow. This species (pic, right) is the only endemic anole on the island of Dominica, and can be found in all of the available environments on the island.
Dominican anoles can be found in cool, wet cloud forests (first pic on the right) and hot, dry coastal forest (second pic on the right) where they regularly experience body temperatures that differ by more than 10°C! We are using reciprocal transplant experiments to understand how populations are able to adapt to these different environments in the face of gene flow.
Sexual signal and behavioral evolution
Anoles have a colorful throat fan, called a "dewlap", which is usually much larger in males and that they use to attract females and to deter rival males and potential predators. Interestingly, slender anoles in Panama have a dewlap polymorphism (top pic on left), whereby some individuals have a solid yellow dewlap ("solid" morph) and others have white around the edge ("basal" morph). This trait follows simple Mendelian inheritance with the solid allele being dominant to the basal allele, and there are naturally occurring populations with varying frequencies of each of these morphs.
We are transplanting both morphs to islands that vary in canopy cover (see examples of low versus high canopy cover in bottom two pics) to test the hypothesis that higher light levels reaching the understory select for darker dewlaps. We are tracking survival and reproductive success of each individual to determine how sexual and natural selection jointly determine the frequencies of dewlap morphs.
We are pairing dewlap studies with measurements of female choice, male boldness, and other components of behavior in an attempt to understand how whole suites of behavioral traits evolve when environments change.