Data from: Resource limitation and responses to rivals in males of the fruit fly Drosophila melanogaster

Diet has a profound direct and indirect effect on reproductive success in both sexes. Variation in diet quality and quantity can significantly alter the capacity of females to lay eggs and of males to deliver courtship. Here we tested the effect of dietary resource limitation on the ability of male D. melanogaster to respond adaptively to rivals by extending their mating duration. Previous work done under ad libitum diet conditions showed that males exposed to rivals prior to mating significantly extend mating duration, transfer more ejaculate proteins and achieve higher reproductive success. Such adaptive responses are predicted to occur because male ejaculate production may be limited and hence ejaculate resources require allocation across different reproductive bouts, to balance current versus future reproductive success. However, when males suffer dietary limitation, and potentially have fewer reproductive resources to apportion, we expect adaptive allocation of responses to rivals to be minimised. We tested this prediction and found that males held on agar-only diets for 5-7 days lost the ability to extend mating following exposure to rivals. Interestingly, extended mating was retained in males held on low yeast/sugar: no sugar/yeast diet treatments, but was mostly lost when males were maintained on ‘imbalanced’ diets in which there was high yeast: no sugar and vice versa. Overall, the results show that males exhibit adaptive responses to rivals according to the degree of dietary resource limitation and to the ratio of individual diet components.

饮食对两性的繁殖成功均具有深远的直接与间接影响。饮食质量与数量的差异，可显著改变雌性的产卵能力与雄性的求偶表现效能。本研究探究了膳食资源限制对雄性黑腹果蝇（Drosophila melanogaster）通过延长交配时长以适应性响应竞争者的能力的影响。此前在自由摄食饮食条件下开展的研究表明，交配前暴露于竞争者的雄性果蝇可显著延长交配时长、转移更多射精蛋白，并获得更高的繁殖成功率。此类适应性响应的存在具有理论预测性，因雄性的射精蛋白产生能力存在上限，故射精资源需在不同繁殖回合间进行分配，以平衡当前与未来的繁殖收益。然而，当雄性面临膳食资源限制，且可支配的繁殖资源相对匮乏时，其针对竞争者的适应性响应分配理应被显著削弱。本研究验证了这一预测，结果发现，仅以琼脂为食5至7天的雄性果蝇，在暴露于竞争者后不再具备延长交配时长的能力。有趣的是，接受低酵母/低糖、无糖/低酵母饮食处理的雄性果蝇，仍保留了延长交配时长的能力；但当雄性被饲养于‘失衡’饮食（即高酵母/无糖，或反之高糖/低酵母）条件下时，该能力大多丧失。总体而言，本研究结果表明，雄性果蝇针对竞争者的适应性响应，取决于其面临的膳食资源限制程度以及饮食各组分的配比。