Socio-sexual environment influences fecundity, but not response to bacterial infection, in Drosophila melanogaster females

It is common for a host exposed to a pathogenic infection challenge to exhibit suppression of fecundity. This suppression can be driven by either a resource allocation-based trade-off between fecundity and immune function, or by infection-induced damage to host soma (particularly the reproductive organs). Alternatively, hosts can increase their fecundity to compensate for the curtailed lifespan resulting from lethal infection. Various factors, both extrinsic and intrinsic to the host, determine the actual effect of any infection challenge on host fecundity. While the host’s physiological and abiotic environmental factors have been thoroughly explored in this context, the role of the host’s biotic environment – especially its social and sexual environment – is rarely addressed. We investigated whether the socio-sexual environment (SSE) of D. melanogaster females influenced the effect of bacterial infection on their fecundity. We altered the socio-sexual environment of the females by housing them with different numbers of same-sex and opposite-sex companions. Our results indicate that while such alterations of the SSE changed the baseline reproductive effort of the females, they had no role in determining female susceptibility to infections or how infection affected female fecundity.