The Genetic Basis of Convergence in Neotropical Lepidoptera

Convergent evolution, the repeated evolution of similar traits in independent lineages in response to the same selection pressure, is widespread across the tree of life. Convergence occurs at all scales - from amino acid sequences up to entire ecosystems - and plays a key role in adaptation, diversification and speciation. Understanding the prevalence and pervasiveness of convergent evolution remains a central goal in evolutionary biology, and many studies have described phenotypic convergence at a range of evolutionary timescales. More recently, attempts have been made to understand the genetic mechanisms responsible. “Mimicry rings” of taxa with aposematic warning colouration are a natural experiment in convergent evolution, with shared phenotypes and selective pressures across a large range of evolutionary timescales. These systems provide an excellent opportunity to study the genetics underlying convergent evolution.

I used field studies, phylogenetics, and comparative and population genomics to characterise the traits involved in convergent evolution in Lepidoptera and the genetic mechanisms which contribute to it. I find that, in mimetic neotropical Lepidoptera, convergent evolution extends beyond superficial warning colouration to include a suite of complex flight behaviour traits. The convergent evolution of mimetic colour patterns was found to be reliant on the reuse of two major effect genes, among species that diverged 22, 70 or even 110 million years ago; though there seems to have been little sharing of these alleles through hybridisation and introgression. In addition to reuse of the same genes, I also find that the same genetic architecture has been used to produce analogous local polymorphism in three highly divergent lineages. Overall, independent reuse and adaptation of the same genes is ubiquitous in this system and appears to be the defining contributory mechanism to convergent evolution even across deep evolutionary timescales.