Consequences of population structure for sex allocation and sexual conflict

Abstract

Both sex allocation and sexual conflict can be modulated by spatial structure. However, how the interplay between the type of dispersal and the scale of competition simultaneously affects these traits in sub-divided populations is rarely considered. We investigated sex allocation and sexual conflict evolution in meta-populations of the spider mite Tetranychus urticae evolving under budding (pairing females from the same patch) or random (pairing females from different patches) dispersal and either local (fixed sampling from each subpopulation) versus global (sampling as a function of subpopulation productivity) competition. Females evolving under budding dispersal produced less female-biased offspring sex ratios than those from the random dispersal selection regimes, contradicting theoretical predictions. In turn, the scale of competition did not have a strong effect on sex allocation. Males evolved under budding dispersal induced less female harm than those exposed to random dispersal, but there was no reduction in female fitness following exposure to multiple mates from either selection regime. This work highlights that population structure can impact the evolution of sex allocation and sexual conflict. We also discuss how selection on either trait may reciprocally affect the evolution of the other, for example via effects on fecundity.