The genetic basis of interspecies host preference differences in the model parasitoid, Nasonia

The genetic basis of host preference has been investigated in only a few species, despite its importance to parasitoid evolution and biological control. Here we show that a major locus strongly influences host preference in the parasitic wasp Nasonia. Nasonia attack fly pupae; N. vitripennis is a generalist that utilizes a diverse set of hosts whereas N. giraulti specializes on Protocalliphora (birdnest blowflies). In laboratory choice experiments using Protocalliphora and Sarcophaga (flesh flies), N. vitripennis shows a preference for Sarcophaga while N. giraulti shows a preference for Protocalliphora. Through a series of interspecies crosses we have introgressed a major locus affecting host preference from N. giraulti in N. vitripennis. The N. giraulti allele is dominant and greatly increases preference for Protocalliphora pupae in the introgression line relative to the recessive N. vitripennis allele. We utilize the extensive genomic resources available for Nasonia to pinpoint the locus to a 16 Mbp region of chromosome 4. To our knowledge this is the first introgression of the host preference of one parasitoid species into another, as well as one of the few performed for any insect.