The effect of dominance on polymorphism in Müllerian mimicry

- We investigate the influence of dominance on the maintenance of polymorphism in a Müllerian mimicry system in a spatially heterogeneous environment.
- Complete dominance was shown to extend the parameter space, and thus the breadth of ecological situations, where Müllerian mimicry polymorphism was maintained.
- Overdominance, which promotes polymorphism, can arise given certain levels of toxicity and predator discrimination accuracy.
- Dominant alleles were shown to reach lower frequencies than recessive alleles when selection on both homozygotes was symmetrical.

Dominance controls the phenotype of heterozygous individuals, and plays an important role in the maintenance of polymorphism. Here we focus on the dominance acting on warning-pattern polymorphism in species engaged in Müllerian mimicry. Müllerian mimics are toxic species which display bright colour patterns used as a warning signal to predators and are subject to local positive density-dependent selection. Some Müllerian mimics are polymorphic due to a selection/migration balance in spatially heterogeneous communities of prey. Since heterozygotes at a locus controlling warning pattern might exhibit intermediate, non-mimetic heterozygous morphs, dominance is likely to influence the polymorphism at this locus. Using a deterministic model describing migration, density-dependent predation and reproduction, we investigated the influence of dominance on the dynamics of alleles at locus determining mimetic phenotype. Our results suggest dominance may interact with migration and selection and plays an important role in shaping the conditions of polymorphism persistence and the frequency of alleles at this locus. Our results thus highlight the important role of dominance in the dynamics of polymorphism at loci under balancing selection due to environmental heterogeneity.