Spatial structure imposes sex-specific costs but does not reduce interlocus sexual conflict

Spatial structure is a common feature of all naturally occurring populations. Theoretically, spatial structuring of a habitat could modulate the intensity of interlocus sexual conflict (ISC) in a population, possibly by modulating intersexual encounter rate. We tested this theory using laboratory populations of Drosophila melanogaster by measuring male-induced decline in female fitness in three-patch habitat systems with two alternative habitat types: structured-interconnected and unstructured. Our results on reproductive and survival costs in females suggested significant costs attributable to male presence (i.e. ISC) and to living on structured habitat. However, there was only weak evidence supporting the theory of modulation of ISC by habitat structuring only. Through a follow-up experiment, we also showed that the effect of habitat on ISC is robust to the alteration of female conditions. Therefore, it appears that spatial structuring per se is unlikely to modulate ISC but can impose additional survival costs. We also showed that this survival cost could be sex specific, possibly reflecting female-biased spontaneous dispersal.