Characterising reproductive barriers between three closely related Heliconius butterfly taxa.

Abstract Debates about the possibility of divergence in the face of gene flow have been an ongoing feature in the field of speciation. However, recent theoretical studies and examples in nature have demonstrated evidence for such a process. Much research now focuses on finding more evidence of reinforcement such as stronger isolation in sympatric populations. Genomic studies have also been investigating the role of gene flow in sympatric speciation and the formation of islands of divergence. Heliconius butterflies offer extensive opportunities to answer such questions. Here, I test whether male colour pattern preference and female host plant preference act as reproductive barriers in three Heliconius taxa with varying degrees of geographic overlap. Further experiments on the F2 hybrids of two of these taxa aimed to identify the underlying genomic architecture of these traits. My results suggest that male colour pattern preference and host preference are acting as reproductive barriers. Stronger differences between the sympatric species were found demonstrating evidence for reinforcement and divergence with gene flow. Initial analyses of the F2 hybrid phenotypes suggest that several loci control these traits and pave the way for future genetic analyses to further understand the role of gene flow in speciation