My research focuses on understanding the genetic basis and evolutionary history of biological diversity, using as a model the spectacular adaptive radiation of Heliconius butterflies. Adaptation and speciation are at the core of the evolutionary process and, as such, a major goal of modern research in evolutionary biology is to characterize the genetic basis of adaptive traits and traits that limit reproduction between species. In some biological systems the processes of adaptation and speciation intersect such that divergence between populations that results from differential natural or sexual selection has the effect of limiting reproduction between populations – hence, the genes that underlie adaptation and speciation are one and the same. Such systems provide us with an invaluable tool to study the interplay of natural selection and divergence and they also present us with the rare opportunity to examine the very early stages of the speciation process when it is possible to pinpoint specific changes (and thus specific genes) that are responsible for limiting reproduction between nascent species.
Neotropical butterflies in the genus Heliconius are unpalatable, aposematic, and have undergone a recent adaptive radiation in wing color patterns as a consequence of natural selection for Müllerian mimicry. While the genus Heliconius serves as a classic example of adaptation it also provides a powerful tool to study the interplay of natural selection and speciation and to identify genes that are responsible for the earliest stages of reproductive isolation. This is because adaptive wing pattern divergence, which is the product of predator-imposed selection to match different mimicry rings, has the side-effect of limiting reproduction between divergent wing pattern phenotypes. Given the central role of mimetic wing patterns in generating reproductive isolation in Heliconius butterflies, these phenotypic traits offer excellent opportunities to study the genetic basis of speciation. Using a combination of high-resolution genetic mapping, fine-scale linkage disequilibrium mapping, and comparative analyses of gene expression, my research seeks to identify these speciation genes, characterize their developmental/mechanistic actions, and elucidate the interactions between trait and mate preference evolution.