Data from: Direct benefits of choosing a high fitness mate can offset the indirect costs associated with intralocus sexual conflict

Intralocus sexual conflict generates a cost to mate choice: high fitness partners transmit genetic variation that confers lower fitness to offspring of the opposite sex. Our earlier work in the fruit fly, Drosophila melanogaster, revealed that these indirect genetic costs were sufficient to reverse potential “good genes” benefits of sexual selection. However, mate choice can also confer direct fitness benefits by inducing larger numbers of progeny. Here, we consider whether direct benefits through enhanced fertility could offset the costs associated with intralocus sexual conflict in D. melanogaster. Using hemiclonal analysis, we found that females mated to high fitness males produced 11% more offspring compared to those mated to low fitness males, and high fitness females produced 37% more offspring than low fitness females. These direct benefits more than offset the reduction in offspring fitness caused by intralocus sexual conflict, creating a net fitness benefit for each sex to pairing with a high fitness partner. Our findings highlight the need to consider both direct and indirect effects when investigating the fitness impacts of mate choice. Direct fitness benefits may shelter sexually antagonistic alleles from selection, suggesting a novel mechanism for the maintenance of fitness variation.

基因座内性别冲突（intralocus sexual conflict）会为配偶选择带来演化代价：高适合度（fitness）的伴侣会传递遗传变异，该变异会对其异性后代造成更低的适合度。我们此前在黑腹果蝇（Drosophila melanogaster）中的研究表明，这类间接遗传代价足以抵消性选择潜在的“好基因”收益。不过，配偶选择也可通过提升后代数量带来直接适合度收益。本研究旨在探讨通过增强生育力获得的直接适合度收益，能否抵消黑腹果蝇中基因座内性别冲突带来的代价。我们采用半克隆分析（hemiclonal analysis）方法，发现与高适合度雄蝇交配的雌蝇所产后代数量较与低适合度雄蝇交配的雌蝇高出11%；而高适合度雌蝇所产后代数量较低适合度雌蝇高出37%。这类直接适合度收益远超基因座内性别冲突所导致的后代适合度降幅，使得两性在与高适合度伴侣交配时均能获得净适合度收益。我们的研究结果强调，在探究配偶选择的适合度影响时，需同时考虑直接与间接效应。直接适合度收益或许会庇护性拮抗等位基因（sexually antagonistic alleles）免受选择压力，这为维持适合度变异提供了一种全新的机制。