Genetics of female mate discrimination of heterospecific males in Nasonia (Hymenoptera, Pteromalidae)

Despite its importance to mating system evolution, sexual selection and reproductive isolation, little is known about the genetic basis of female mate choice. We studied the behavioural and genetic basis of interspecific mate discrimination in Nasonia wasps, using two strains of N. longicornis (LCa and LId) that differ in female acceptance of males from the sibling species N. vitripennis. Both strains showed low acceptance (≤2%) of N. vitripennis males in the first courtship, but acceptance by LId females subsequently increased (11% by the second and 15% by the third courtship), whereas acceptance by LCa females remained low (≤2%). After 2 h of exposure to a N. vitripennis male, 59% of LId females mated compared with only 8% of LCa females. Interstrain cross F1 females showed significantly higher acceptance of N. vitripennis males than either parental strain in the first courtship (15-29%) and after 2 h (79-82%). A genetic analysis of acceptance at 2 h revealed three major quantitative trait loci (QTL). For each major QTL, the allele that increased female mate acceptance was dominant. The QTL with the largest effect accounted for half the strain difference, and was confirmed by additional crosses. This QTL was involved in the females' continued reluctance to mate with N. vitripennis males during multiple courtships. Results are discussed in terms of the behavioural and genetic architecture of female mate discrimination and possible implications to the evolution of courtship, mating systems and reproductive isolation.