Résumé
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.