Tinamou egg color displacement at eco-geographical and song space overlap

The divergence of reproductive traits frequently underpins the evolution of reproductive isolation. Here we investigated the hypothesis that tinamou (Tinamidae) egg coloration functions as a mating signal and its diversification was driven by reinforcement. For many tinamou species, the male guards the nest that is sequentially visited and laid eggs in by multiple females. The colorations of the existing eggs in the nest could signal mate quality and species identities to both the incubating male and the upcoming females, preventing costly hybridization, thus were selected to diverge among species (Mating Signal Character Displacement Hypothesis). If so, two predictions should follow: (1) egg colors should coevolve with known mating signals as the tinamou lineages diverged; (2) species that partition similar eco-geography should display different egg colors. The tinamou songs are important mating signals and are highly divergent among species. We found that the egg color was significantly associated with the first principal component of the song variables. In addition, tinamou species with similar eco-geography tend to display different egg colors, while controlling for song variation among species. Mating signal evolution could be opportunistic and even exploit post-mating trait as premating signals that undergo character displacement in sympatry.