Warning signals are seductive: Color outperforms pattern for both predator avoidance and mate attraction in Heliconius butterflies

Visual signaling in animals can serve many uses, including predator deterrence and mate attraction. In many cases aposematic signals used to advertise unprofitability to predators are also used for intraspecific communication. Although aposematism and mate choice are significant forces driving the evolution of many animal phenotypes, the relative levels of cooperation or conflict between relevant visual cues remains little explored. Here we address this question in the aposematic passion-vine butterfly Heliconius erato by using color and pattern-manipulated models to test the contributions of different visual cues to both mate choice and warning coloration. We found that the relative effectiveness of a model at escaping predation was the same as its effectiveness at attracting mates, and in both cases wing color cues outperformed wing pattern cues. Overall, however, a combination of the appropriate color and pattern cues performed best for both predator deterrence and mate attraction. By exploring the relative contributions of color versus pattern in predation and mate preference studies, we have shown how both natural and sexual selection can work together to favor the evolution of specific butterfly color patterns.