Interaction of Drosophila and its endosymbiont Wolbachia: Natural heat shock and the overcoming of sexual incompatibility

Wolbachia, a bacterial endosymbiont of diverse arthropods, affects its host 's reproduction and so is consequential for its host's fitness. In the frui t fly Drosophila simulans, Wolbachia increases embryonic mortality in cross es of infected males with uninfected females, possibly by manipulating the proteins of the host gametes, Preliminary data suggests these proteins incl ude at least two families of heat-shock proteins, Hsp70 and Hsp90. Drosophi la larvae live within necrotic fruit, in which larvae can experience therma l stress that induces Hsp expression. Infected male D. simulans, if exposed to laboratory heat shock as larvae, father more viable offspring than unex posed controls, Also, infected male D. simulans, if allowed to copulate bef orehand, father more viable offspring than virgin controls of identical age . These two mechanisms of restoring the reproductive compatibility of Wolba chia-infected Drosophila could affect the fitness of wild D. simulans; we a re attempting to document these effects through modelling and experimental study of natural populations and their thermal environment. This research p rogram exemplifies how evolutionary physiology may extend far beyond the cl assical disciplinary boundaries of physiology and evolutionary biology.