Mapping of hybrid incompatibility loci in Nasonia

According to theory, F-2 hybrid breakdown (lethality or sterility) is due t o incompatibilities between interacting genes of the different species (i.e ., the breaking up of coadapted gene complexes). Detection of such incompat ibilities is particularly straightforward in haplodiploid species, because virgin F-1 hybrid females will produce haploid recombinant F-2 males. This feature allows for screening of the complete genome for recessive genetic i ncompatibilities. Crosses were performed between Nasonia vitripennis (v) an d its sibling species N. giraulti (g). First, a linkage map was produced us ing RAPD markers. RAPD markers showed an overall bias toward vitripennis al leles, a pattern not predicted by the basic two-interactor Dobzhansky-Mulle r model. Recovery patterns of visible markers were consistent with those of linked RAPD markers. If particular genetic interactions between two loci a re causing hybrid lethality, then those genotypes should be underrepresente d or absent among adult F-2 males. Four sets of significant incompatibiliti es were detected by performing pairwise comparisons of markers on different chromosomes. Likely explanations for the observed patterns are maternal ef fect-zygotic gene incompatibilities or clustering of incompatibility loci. Due to the short generation time, advantages of haplodiploidy, and availabi lity of markers, Nasonia promises to be a productive system for investigati ng the genetics of hybrid inviability.