Temperature effects on emergence time, proportion of males, and diapause in three species of Nasonia (Hymenoptera: Pteromalidae)

Temperature has been demonstrated to induce phenotypic plasticity in numerous insects for numerous traits. An organism of a specific genotype is said to exhibit phenotypic plasticity if it shows variation in a trait or traits that is dependant on changes in the external environment. A reaction norm is the function that relates the environments to which a particular genotype is exposed and the phenotypes that can be produced by that genotype. Genotype-by-environment interactions measure how genotypes vary in their· reaction norms. Trait responses to temperature can be examined with analyses that test for G by E interactions and display norms of reaction; thus telling us if different genotypes behave differently in different temperature environments. In the genus Nasonia, females produce large numbers of virtually identical offspring in a single clutch, making them ideal for a study of reaction norms. Nasonia vitripennis, N. giraulti and N. /ongicomis are parasitic wasps that parasitize various species of blow flies. I tested two strains of each of the three species for differences in emergence time, proportion of males and tendency to diapause due to different temperature environments. I also tested for genetic differences among the strains and any G by E interactions that might occur. I found that emergence time was the same for all species and all strains tested; as temperature increased the emergence time decreased. The proportion of males per clutch tended to have less of a plastic response, but there is evidence of a genetic response, with strains of the same species behaving differently. Diapause showed more genetic than temperature variation. In general, the G by E responses were modest.