The limits of evolutionary convergence in sympatry: reproductive interference and developmental constraints leading to local diversity in warning traits

Abstract

AbstractMutualistic interactions between defended species represent a striking case of evolutionary convergence in sympatry, driven by the increased protection against predators brought by mimicry in warning traits. However, such convergence is often limited: sympatric defended species frequently display different or imperfectly similar warning traits. The phylogenetic distance between sympatric species may indeed prevent evolution towards the exact same signal. Moreover, warning traits are also involved in mate recognition, so that trait convergence might result in heterospecific courtship and mating. Here, we develop a mathematical model to investigate the strength and direction of evolution of warning trait in defended species with different ancestral traits. Specifically, we determine the effect of phenotypic distances between ancestral trait states of sympatric defended species, and costs of heterospecific sexual interactions on imperfect mimicry and trait divergence. Our analytical results confirm that reproductive interference limits the convergence of warning traits, leading to either complete divergence, or imperfect mimicry, but only between species with different ancestral traits. Surprisingly, our model pinpoints that, depending on the relative species densities, the mimic/model relationships between sympatric species can be inverted. Our study suggests that reproductive interference may promote the emergence of novel warning traits, enhancing mimetic diversity.