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.

基因座内性冲突（intralocus sexual conflict）会为配偶选择带来适配度代价：高适配度的伴侣会传递遗传变异，这些变异会令异性后代的适配度降低。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“优秀基因”收益。不过，配偶选择也可通过产生更多后代而带来直接适配度收益。本研究旨在探究通过提升繁殖力获得的直接收益，是否能够抵消黑腹果蝇中基因座内性冲突带来的代价。本研究采用半克隆分析（hemiclonal analysis）方法，结果发现：与高适配度雄性交配的雌性所产后代数量，比与低适配度雄性交配的雌性多出11%；而高适配度雌性的后代数量也比低适配度雌性多出37%。这类直接收益完全抵消了基因座内性冲突所导致的后代适配度下降，使得两性在与高适配度伴侣交配时均能获得净适配度收益。本研究结果表明，在探究配偶选择对适配度的影响时，需同时考虑直接效应与间接效应。直接适配度收益可能会使性拮抗等位基因免受选择压力，这为适配度变异的维持提供了一种全新的机制。