Balancing selection in Müllerian mimicry: causes and consequences

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• Dr Violaine Llaurens, Muséum National d’Histoire Naturelle Institut de Systématique, Evolution, Biodiversité
• Tuesday 10 March 2015, 16:00-17:00
• Part II Lecture Theatre, Department of Zoology.

If you have a question about this talk, please contact Dr Hannah Rowland.

Mimicry among toxic species is a textbook example of natural selection driving evolutionary convergence of complex traits. Most toxic species involved in such Müllerian mimicry display a single warning signal within population because of selection exerted by predators, fixing the most common signal. Surprisingly, in the toxic butterfly Heliconius numata, several warning patterns are maintained within localities, and each display high resemblance with distasteful species from different communities. During this talk, I will first explore several hypotheses on the origin of balancing selection in this species. First, weak toxicity of H. numata might favour disruptive selection on warning patterns, because each warning pattern will mimic a different group of toxic species, thus limiting the impact of lack of toxicity on the efficiency of the warning signal. I will thus present empirical estimation on toxicity variations in H. numata and its effect on birds’ predation behaviour. Then I will present some theoretical results on the role of disassortative mating as a selective pressure promoting local polymorphism of warning pattern. Finally, I will investigate the consequences of this balanced polymorphism on the underlying genetic architecture. Variations in warning pattern in H. numata are controlled by a supergene P in which each allele encodes for a different mimetic pattern. As a consequence of this polymorphism, a high number of heterozygote are present in natural population and promote strict dominance between mimetic allele as a response to selection exerted against intermediate non-mimetic of heterozygotes. I will show results from RNAseq investigating the molecular basis of such dominance at the supergene P.

This talk is part of the Behaviour, Ecology & Evolution Seminar Series series.

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