Mimicry in Heliconius and Ithomiini butterflies: The profound consequences of an adaptation

¹ Institut de Systématique, Évolution, Biodiversité ISYEB – UMR 7205 – CNRS, MNHN, UPMC, EPHE Muséum national d'Histoire naturelle, Sorbonne Universités 57 rue Cuvier, CP. 50, 75005 Paris, France
² Centre d'Ecologie Fonctionnelle et Evolutive, CEFE UMR 5175 CNRS – Université de Montpellier – Université Paul-Valéry Montpellier – EPHE 1919 route de Mende, 34293 Montpellier Cedex 5, France

^a Corresponding author: elias@mnhn.fr

Abstract

Prey populations have evolved multiple strategies to escape predation. Camouflage is a strategy resting on avoiding detection by potential predators, whereas aposematism relies on advertising chemical defences with conspicuous warning signals. While camouflaged phenotypes are subject to negative frequency-dependent selection, aposematic preys are under positive frequency-dependence, where the efficiency of a signal increases with its own local abundance. Because of his “strength-in-number” effect, multiple chemically-defended species exposed to the same suite of predators gain a selective advantage from converging on the same warning signals. Convergence in warning signals is called Müllerian mimicry. Here, we review the results of recent genetic and ecological research on two well-studied groups of neotropical Müllerian mimetic butterflies, the genus Heliconius and the tribe Ithomiini, which advertise their unpalatability through conspicuous wing colour patterns. Mimicry represents a major adaptation in these groups, where the effects of selection extend well beyond mere phenotypic resemblance. Selection acts on other traits used as mating cues, on the genetic architecture of colour pattern and even on the ecological niche of species. The origin of mimicry itself and the coexistence of multiple mimicry patterns are well understood, but the ultimate drivers of mimicry diversity remain unclear.