Females manipulate behavior of caring males via prenatal maternal effects [Evolution]

In species with biparental care, there is sexual conflict as each parent is under selection to minimize its personal effort by shifting as much as possible of the workload over to the other parent. Most theoretical and empirical work on the resolution of this conflict has focused on strategies used by both parents, such as negotiation. However, because females produce the eggs, this might afford females with an ability to manipulate male behavior via maternal effects that alter offspring phenotypes. To test this hypothesis, we manipulated the prenatal conditions (i.e., presence or absence of the male), performed a cross-fostering experiment, and monitored the subsequent effects of prenatal conditions on offspring and parental performance in the burying beetle Nicrophorus vespilloides. We found that offspring were smaller at hatching when females laid eggs in presence of a male, suggesting that females invest less in eggs when expecting male assistance. Furthermore, broods laid in the presence of a male gained more weight during parental care, and they did so at the expense of male weight gain. Contrary to our expectations, males cared less for broods laid in the presence of a male. Our results provide experimental evidence that females can alter male behavior during breeding by adjusting maternal effects according to prenatal conditions. However, rather than increasing the male’s parental effort, females appeared to suppress the male’s food consumption, thereby leaving more food for their brood.