Elucidating the genetic basis of adaptations in natural populations is central to understanding the origins of biological diversity. One issue of particular importance is whether changes in the same genes underlie the independent evolution of similar adaptations in different species. Butterflies display a massive array of wing patterns, but much of this diversity appears to be a result of variations on a conserved developmental ground plan. This collaborative project will characterize the genetic basis of color patterning across Heliconius, Limenitis, and Papilio butterflies using a novel strategy that combines traditional experimental crosses with modern advances in genomics. This approach will allow the researchers to identify the specific genes responsible for wing patterning in each species and directly test the hypothesis that a core set of genes controls wing patterning across all butterflies.
Wing pattern diversity is widespread across the entire butterfly phylogeny, providing an unparalleled opportunity to explore the genetics and evolution of adaptation, patterning, parallelism, and convergence across a group that has been evolving and radiating for 100 million years. This project will significantly expand the current understanding of how chance and constraint interact to generate biological diversity by examining, in an integrated and comprehensive way, how diverse lineages generate similar morphologies in response to similar selective pressures. This project will also have a variety of important broader impacts related to the training of post-doctoral researchers, graduate students, and undergraduate students, as well as scientific outreach aimed at elementary, middle, and high school students.
Elucidating the genetic basis of adaptive phenotypic variation is central to our understanding of how biological diversity arises. The goal of this project was to identify the specific genetic changes underlying the repeated evolution of similar mimetic wing pattern phenotypes among distantly related butterfly lineages: Heliconius, Limenitis, and Papilio. Our results indicate that the same gene, WntA, is responsible for the evolution of similar mimetic wing patterns in Heliconius and Limenitis, two butterfly lineages that diverged more than 65 million years ago. Furthermore, we demonstrated that similar mimetic variation in the butterfly genus Papilio is controlled by differential expression of a different gene, doublesex, which is typically associated with sex-determination in animals. These findings are remarkable for two reasons. First, evidence that the same gene, WntA, controls variation in the same wing pattern trait in both Heliconius and Limenitis is surprising given the long history of evolutionary divergence between these two lineages (65 mya); a result that implies an unprecedented level of predictability to the evolutionary process. Second, the co-option of doublesex to produce mimetic wing pattern variation in Papilio butterflies (a lineage that diverged from Heliconius and Limenitis ~ 125 mya), while also surprising, nicely illustrates the genetic and developmental flexibility of organisms in response to simiar selective pressures (i.e. - natural selection for mimicry). Collectively, our results provide rare insights into the specific genetic changes underlying examples of convergent evolution. Futhermore, they provide a fascinating portait of how natural selection shapes the evolution of adaptive traits whose divergence contributes to speciation across both micro and macroevolutionary timescales. Finally, our project also resulted in a variety of broader impacts, which included: scientific publications, undergraduate and graduate student training, postdoctoral mentorship and professional development, K-12 education, and public engagement in science through invited seminars and talks.
