Genetic dissection of assortative mating behavior

Abstract

The evolution of new species is made easier when traits under divergent ecological selection are also mating cues. Such ecological mating cues are now considered more common than previously thought, but we still know little about the genetic changes underlying their evolution, or more generally about the genetic basis for assortative mating behaviors. The warning patterns of Heliconius melpomene and H. cydno are under disruptive selection due to increased predation of non-mimetic hybrids, and are used during mate recognition. We carried out a genome-wide quantitative trait locus (QTL) analysis of preference behaviors between these species and showed that divergent male preference has a simple genetic basis. Three QTLs each explain a large proportion of the differences in preference behavior observed between the parental species. Two of these QTLs are on chromosomes with major color pattern genes, including one that is tightly associated with the gene optix. Different loci influence different aspects of attraction, suggesting that behavioral isolation in Heliconius involves the evolution of independently segregating modules, similar to those for the corresponding wing pattern cues. Hybridization and subsequent sharing of wing pattern loci has played an important role during adaptation and speciation in Heliconius butterflies. The existence of large effect preference loci could similarly assist the evolution of novel behavioral phenotypes through recombination and introgression, and should facilitate rapid speciation.