Ecological Divergence and Convergence
Repeated convergent evolution has captured the interest of generations of biologists in part because it implies some degree of determinism in evolution, whether through natural selection toward common adaptive peaks or shared evolutionary constraints. Although phenotypic convergence is a widely occurring phenomenon, our understanding of the degree of overlap between phenotypic convergence and convergence in the underlying cellular, developmental, and genetic architecture is limited. I am leveraging the striking phenotypic convergence across the Lesser Antillean anoles to examine the interplay of evolutionary scales and the overlap of genetic, cellular, and phenotypic patterns of convergence. The Lesser Antilles were independently colonized by two divergent groups of Anolis. The Windward Islands were colonized by the roquet series from South America, whereas the Leeward Islands were colonized by the bimaculatus series from the Greater Antilles. Each island consists of one or two Anolis species, which display remarkable within-species phenotypic variation despite high levels of gene flow between populations and strong phenotypic convergence in response to similar xeric-mesic environmental gradients across islands. Thus, the Lesser Antillean anoles provide an opportunity to conduct comparative studies of adaptive color convergence at various phylogenetic scales (across populations, across closely-related species, and across distantly-related clades).
DNA Methylation and Adaptive Evolution
Regulation of gene expression through DNA methylation is important for several phenomena, including acclimation to environmental stressors, genomic imprinting, and mammalian X-chromosome inactivation. Recent recognition that epigenetic modifications themselves can be heritable and the ability for selection to act upon underlying genetic controls of methylation-mediated plasticity have generated substantial interest in the role of epigenetics in evolution. Yet, to date this work has focused on functional studies within individual species rather than broader evolutionary patterns of DNA methylation. The adaptive radiation of Caribbean Anolis lizards provides an appealing system for such comparative studies due to the repeated convergent evolution of ecomorphs, groups of species which occupy highly similar ecological and morphological space. Thus, I am taking advantage of the Anolis adaptive radiation to examine the role of DNA methylation in facilitating either convergent evolution or adaptive divergence between species.