The joint effect of temperature and host species induce complex genotype-by-environment interactions in the larval parasitoid ofDrosophila,Leptopilina heterotoma(Hymenoptera: Figitidae)

Phenotypic plasticity and genotype-by-environment interactions are usually studied by testing environmental factors separately. However, several environmental factors may vary simultaneously across the geographic range of a species, and thus interact to drive phenotypic and genotypic evolution. Here, we address the question of the interaction between two environmental factors in the case of a koinobiont parasitoid of Drosophila, Leptopilina heterotoma (Hymenoptera: Figitidae). Using two allopatric parasitoid lines, we analysed the joint effect of developmental temperature and host species on two major fitness components (pre-imaginal survival and fecundity) of emerged parasitoids. Our results indicate that both environmental factors strongly interact to shape the parasitoid phenotype. Moreover, complex genotype-by-environment interactions appeared that can even invert the relative fitness of the two parasitoid lines.