Sex,competition and mimicry: an eco-evolutionary model reveals unexpected impacts of ecological interactions on the evolution of phenotypes in sympatry

Phenotypic evolution in sympatric species can be strongly impacted by species interactions, either mutualistic or antagonistic. Heterospecific reproductive behaviours between sympatric species have been shown to favour phenotypic divergence of traits used as sexual cues. Those traits may also be involved in local adaptation or in other types of species interactions and, as a result, undergo complex evolutions across sympatric species. Here we focus on mimicry and study how reproductive interference may impair phenotypic convergence between species with various levels of defence. We use a deterministic model assuming two sympatric species where individuals can display two different warning colour patterns. This eco-evolutionary model explores how ecological interactions shape phenotypic evolution within sympatric species. We investigate the effect of 1) the opposing density-dependent selections exerted on colour patterns by predation and reproductive behaviour and 2) the impact of relative species and phenotype abundances on the fitness costs faced by each individual depending on their species and phenotype. Our model shows that reproductive interference may limit the convergent effect of mimetic interactions and may promote phenotypic divergence between Müllerian mimics. The divergent and convergent evolution of traits also strongly depends on the relative species and phenotype abundances and levels of trophic competition, highlighting how the eco-evolutionary feedbacks between phenotypic evolution and species abundances may result in strikingly different evolutionary routes.