The genetic basis of convergence across evolutionary time

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Convergent evolution, the independent acquisition of similar traits in multiple lineages in response to the same selective pressures, is ubiquitous, facilitating adaptation and diversification across the tree of life. Therefore, understanding the genetic mechanisms by which convergence occurs is critical if we are to understand adaptations that already exist, and the predictability of evolution in response to common selection pressures. We propose to study mimetic convergence across the Lepidoptera using high-throughput sequencing and gene expression analyses to address a major challenge in this field: the contributions of different genetic mechanisms to convergence across evolutionary timescales. This will be the first genetic analysis of convergence for a trait evolving under the same selective force over 2-110 million years of evolution and will uncover the genetic landscape of convergence across evolutionary time.The genetic changes causing convergence can be categorized as divergent genetic mechanisms, parallel evolution, or collateral evolution. We hypothesize that these three processes act at different evolutionary time scales. Most recent understanding of convergent evolution has focused on parallel and collateral evolution among closely related species. We lack studies that investigate the genetic basis of convergence over a range divergence times (from recent to deep time) for a single trait under the same selective force. Only by considering convergence among lineages that split anywhere from a few million to 100 million years ago, or more, can we understand the overall frequency distribution of the genetic mechanisms of convergence. The relative contributions of the three genetic mechanisms will impact on the tempo and direction of evolutionary convergence. For example, interspecific hybridization can greatly facilitate convergence among closely-related species, yet its contribution to convergence is largely unknown. We also lack knowledge of the genetic basis of deep time convergence. An important unanswered question is whether convergence between distant lineages is difficult to evolve. Alternatively, is convergence aided by the existence of conserved genetic architectures and developmental pathways, which may facilitate parallel evolution even after 100 million years of separation? We propose to tackle these fundamental questions about the genetic mechanisms of convergence by exploiting a unique system in the Lepidoptera in which multiple species have converged on the same defensive wing colour patterns across a wide range of evolutionary timescales (2-110 million years). We will use a combination of fieldwork, gene expression analysis and the latest high-throughput sequencing technologies to identify and verify genes responsible for convergence in multiple butterfly and moth species. These data will allow us to assess the relative contributions of divergent genetic mechanisms, parallel and collateral evolution to convergence among 18 species of butterflies and moths representing 2-110 million years of evolution, and will allow us for the first time to visualize the genetic landscape of convergent evolution for a single trait evolving under the same selective force across a wide evolutionary timescale.