Condition-transfer maternal effects modulate inter-locus sexual conflict

Strong sexual selection frequently favors males that increase their reproductive success by harming females, with potentially negative consequences for natural populations. Understanding what factors modulate conflict between the sexes is hence critical to understand both the evolution of male and female phenotypes and the viability of populations in the wild. Here, we model the evolution of male harm while incorporating male-induced maternal effects on offspring quality. We show that because male harm can induce condition-transfer maternal effects that reduce the quality of a harming male's own offspring, maternal effects can partially align male and female evolutionary interests and significantly curb the evolution of male harm. These effects are independent of relatedness, the scale of competition, mating system, and whether male harm comes before (i.e., harassment) and/or during/after (i.e., traumatic inseminations or toxic ejaculates) mating and are particularly salient when maternal effects influence offspring ability to inflict (sons) or resist (daughters) harm. Our results underscore the potential importance of considering maternal effects to unravel the evolution of sexual conflict.