The evolution and genetics of sexually dimorphic ‘dual’ mimicry in the butterflyElymnias hypermnestra

Sexual dimorphism is a major component of morphological variation across the tree of life, but the mechanisms underlying phenotypic differences between sexes of a single species are poorly understood. We examined the population genomics and biogeography of the common palmflyElymnias hypermnestra , a dual mimic in which female wing colour patterns are either dark brown (melanic) or bright orange, mimicking toxicEuploea andDanaus species, respectively. As males always have a melanic wing colour pattern, this makesE. hypermnestra a fascinating model organism in which populations vary in sexual dimorphism. Population structure analysis revealed that there were three genetically distinctE. hypermnestra populations, which we further validated by creating a phylogenomic species tree and inferring historical barriers to gene flow. This species tree demonstrated that multiple lineages with orange females do not form a monophyletic group, and the same is true of clades with melanic females. We identified two single nucleotide polymorphisms (SNPs) near the colour patterning geneWntA that were significantly associated with the female colour pattern polymorphism, suggesting that this gene affects sexual dimorphism. GivenWntA 's role in colour patterning across Nymphalidae,E. hypermnestra females demonstrate the repeatability of the evolution of sexual dimorphism.