Genotype-by-genotype specificity remains robust to average temperature variation in an aphid/endosymbiont/parasitoid system

Genotype-by-genotype interactions demonstrate the existence of variation upon which selection acts in host-parasite systems at respective resistance and infection loci. These interactions can potentially be modified by environmental factors, which would entail that different genotypes are selected under different environmental conditions. In the current study, we checked for a G x G x E interaction in the context of average temperature and the genotypes of asexual lines of the endoparasitoid wasp Lysiphlebus fabarum and isolates of Hamiltonella defensa, a protective secondary endosymbiont of the wasp's host, the black bean aphid Aphis fabae. We exposed genetically identical aphids harbouring different isolates of H. defensa to three asexual lines of the parasitoid and measured parasitism success under three different temperatures (15°C, 22°C and 29°C). While there was clear evidence for increased susceptibility to parasitoids at the highest average temperature and a strong G x G interac...