Genetics of wing size differences between two Nasonia species

Very little is known about the genetics of morphological differences betwee n species; This study investigates the genetic basis of a significant morph ological difference between males of two closely related species of the par asitoid,wasp Nasonia. One of the defining characters of species in the genu s Nasonia is:male forewing size. The forewings of Nasonia giraulti males ar e 2.4 times larger than the forewings of Nasonia vitripennis males. Genetic analysis of hybrids between these species indicates that this difference i s due to the effect of a few genes, Also discussed is the possible role of 'pseudo linkage' in analysis of F-2 hybrids, Pseudo linkage occurs when gen es affecting a trait are linked to interacting hybrid lethal loci, and can lead to an;overestimation of the number of regions involved in a phenotype. The large wing trait of N. giraulti was introgressed into a N. vitripennis background. Analysis of this introgression line indicates that 44% of the difference in wing size between the species is due to the presence of a sin gle gene, or a few tightly linked genes, located on linkage group IV. Furth ermore, the introgressed region appears to affect the width of the wing mor e strongly than the length. Indirect results suggest that this region affec ts wing cell size, rather than cell number. Results are consistent with the view that morphological and adaptive differences between species can have a simple genetic:basis.