Genetic architecture of prezygotic reproductive isolation in the parasitic wasp genus Nasonia

My thesis contributes to the understanding of the evolution of reproductive isolation which is an important topic in speciation biology. I have investigated how reproductive isolation barriers become established with a focus on the role of mating behaviour and pheromones in sexual isolation and species recognition. I used the model system of Nasonia parasitoid wasps with four species, N. vitripennis, N. longicornis, N. giraulti, and N. oneida, that differ in degrees of prezygotic isolation. These species show intraspecific and interspecific variation in mating behaviour (courtship behaviour and courtship song) and chemical communication signals (sex pheromones and cuticular hydrocarbons). I for the first time described the mating behaviour of N. oneida, and provided detailed descriptions of male courtship song for all four Nasonia species. European populations of N. vitripennis showed geographical variation in courtship traits and cuticular hydrocarbon profiles that was partly correlated with latitude. The genetic basis of male and female mating signals was investigated with quantitative trait locus (QTL) analysis of a cross between N. giraulti and N. oneida using neutral and candidate gene single nucleotide polymorphism (SNP) markers. It demonstrated quantitative differences in male sex pheromones and male mating behaviour between the species that affect female receptivity. Lack of female interspecific mate discrimination QTL pointed at a polygenetic basis for female choice with strong environmental effects.