PARALLEL EVOLUTION IN THREESPINE STICKLEBACK
Convergence onto similar phenotypes in similar environments by independent species or populations is strong evidence for evolution by natural selection. Often, evolutionary ecologists focus on those traits that are evolving most in parallel. Multi-trait, quantitative approaches to parallel evolution that ask how much parallelism there is, and why, are more rare.
In Dan Bolnick’s lab at UT Austin, and in collaboration with Catherine Peichel and Andrew Hendry, I am studying populations of threespine stickleback adapting to lake and stream environments replicated across 16 different watersheds on Vancouver Island, BC, Canada. We are investigating the ecology, morphology, and genetics of these populations to estimate the degree of parallelism, and non-parallelism, and to understand the factors underlying such evolution. We are also beginning to investigate parallelism in natural selection, and how that might underlie parallelism in ecology, morphology, and genetics.
CHARACTER DISPLACEMENT IN ANOLIS CAROLINENSIS
I am studying whether and how the native lizard Anolis carolinensis (top left) is responding evolutionarily to the recent invasion of A. sagrei (top right) to small spoil islands in Mosquito Lagoon, Florida. Anolis carolinensis naturally occurs on every island in the lagoon. I compared the habitat use and morphology of A. carolinensis populations on six islands where A. sagrei has invaded sometime since 1994 (the treatments) to five islands where A. carolinensis is the only anole (the controls).
Data from this natural experiment show that A. carolinensis perches higher in the presence of A. sagrei and also has larger toepads with more clingy lamellae. This is consistent with our predictions for arboreal anoles and represents rapid evolution by a native species in response to an invader. A common garden experiment suggests that these toepad differences are evolved. We have also ruled out alternative explanations like chance or environmental differences among treatments. (Lizard photos by C. Gilman.)
THE GENETIC BASIS OF DEWLAP COLOR IN ANOLIS DISTICHUS
In collaboration with Adam Freedman and the Hoekstra lab, I am working on a project targeting the genetic basis of color variation in the dewlap (an extensible throat fan) of populations of Anolis distichus from eastern Dominican Republic. We are working at a transition zone between two subspecies of A. distichus: A. d. inigularis (right, top) and A. d. properus (right, bottom). As you can see from the images, the two subspecies have very differently colored dewlaps.
At the transition zone, the populations are admixing to create phenotypic variation in dewlap color and pattern (right, middle). We are hoping to associate this natural phenotypic variation with genetic variation at thousands of loci from across the genome sequenced using ddRAD methodology.