Species specificity and intraspecific variation in the chemical profiles of Heliconius butterflies across a large geographic range

Most of the sequences in this study were provided by Krysztof Kozak. Traits important for mate choice and behavioural isolation are predicted to be under strong stabilising selection within species, however such traits can also exhibit variation at the population level driven by neutral and adaptive evolutionary processes. Here, we describe patterns of divergence among androconial and genital chemical profiles at inter- and intra-specific levels in mimetic Heliconius butterflies. Most variation in chemical bouquets was found between species, but there were also quantitative differences at the population level. The strength of the correlation between chemical and the genetic divergence varies between species and is generally stronger for genital than for androconial chemical profiles. We identified "indicator" compounds characteristic of particular species that included known biologically active compounds, suggesting a promising approach for identification of candidate compounds for future behavioural studies in novel systems. Overall, the strong signal of species identity suggests a role for these compounds in species recognition, but with additional neutral variation at the population level.