Cryptic differences in colour among Müllerian mimics: how can the visual capacities of predators and prey shape the evolution of wing colours?
Antagonistic interactions between predators and prey often lead to co-evolution. In the case of toxic prey, aposematic colours act as warning signals for predators and play a protective role. Evolutionary convergence in colour patterns among toxic prey evolves due to positive density-dependent selection and the benefits of mutual resemblance in spreading the mortality cost of educating predators over a larger prey assemblage. Comimetic species evolve highly similar colour patterns, but such convergence may interfere with intraspecific signalling and recognition in the prey community, especially for species involved in polymorphic mimicry. Using spectrophotometry measures, we investigated the variation in wing coloration among comimetic butterflies from distantly related lineages. We focused on seven morphs of the polymorphic species Heliconius numata and the seven corresponding comimetic species from the genus Melinaea. Significant differences in the yellow, orange and black patches of the wing were detected between genera. Perceptions of these cryptic differences by bird and butterfly observers were then estimated using models of animal vision based on physiological data. Our results showed that the most strikingly perceived differences were obtained for the contrast of yellow against a black background. The capacity to discriminate between comimetic genera based on this colour contrast was also evaluated to be higher for butterflies than for birds, suggesting that this variation in colour, likely undetectable to birds, might be used by butterflies for distinguishing mating partners without losing the benefits of mimicry. The evolution of wing colour in mimetic butterflies might thus be shaped by the opposite selective pressures exerted by predation and species recognition.
Institut de Systématique, Evolution et Biodiversité, Département systématique et evolution, UMR 7205, Centre National de la Recherche Scientifique, Museum National d'Histoire Naturelle, Bâtiment d'entomologie, Paris, France.
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Llaurens
Institut de Systématique, Evolution et Biodiversité, Département systématique et evolution, UMR 7205, Centre National de la Recherche Scientifique, Museum National d'Histoire Naturelle, Bâtiment d'entomologie, Paris, France.
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M
Joron
Laboratoire Mécanismes Adaptatifs: des Organismes aux Communautés, Département d'Ecologie et Gestion de la Biodiversité, UMR 7179, Centre National de la Recherche Scientifique, Museum National d'Histoire Naturelle, Brunoy, France.
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Théry
D000818:Animals; D005075:Biological Evolution; D002080:Butterflies / Q000235:genetics*; D003116:Color; D011235:Predatory Behavior; D013053:Spectrophotometry; D014921:Wings, Animal
Heliconius; Melinaea; aposematism; chromatic contrast; co-evolution; species recognition; toxicity; visual system