Abstracts (first author)
Investigating the role of dominance in the polymorphism of wing colour patterns in the mimic butterfly Heliconius numata
Dominance is a widespread mechanism by which the phenotype of heterozygotes is determined. In polymorphic loci, dominance thus plays an important role in the dynamic of the phenotypic polymorphism because of the high number of heterozygotes. This talk focuses on dominance in a striking case of colour polymorphism caused by Müllerian mimicry. In the unpalatable butterfly species Heliconius numata, several wing colour patterns are co-existing and these patterns exhibit high resemblance with other unpalatable species. Colour patterns thus seem to act as a warning signal of toxicity for predators. In H. numata, this protective mimicry is adapted to the spatial variation in communities of unpalatable butterflies, leading to a stable polymorphism of wing colour patterns due to selection/migration equilibrium. These complex wing colour patterns are mainly controlled by a single locus, the supergene P, which contains about 18 co-segregating genes. Dominance relationships among the haplotypes at the supergene P are predicted to be under high selective constraint due to an increased predation risk for non-mimetic intermediate heterozygotes. Using an original morphological approach based on automatic detection of pattern variation, we quantify the coefficient of dominance between haplotypes at the supergene P. The study of controlled crosses between sympatric and allopatric morphs suggests a complete dominance among haplotypes occurring within populations whereas mosaic of dominance is mainly observed in allopatric haplotypes. This highlights the important role of dominance in the polymorphism of distinct wing colour patterns involved in mimicry relationships and allow us to open research on the possible mechanisms of dominance at the supergene P.