Costs and benefits of giant sperm and sperm storage organs in Drosophila melanogaster

In Drosophila, long sperm are favoured in sperm competition based on the length of the female’s primary sperm storage organ, the seminal receptacle (SR). This sperm-SR interaction, together with a genetic correlation between the traits, suggests that the coevolution of exaggerated sperm and SR lengths may be driven by Fisherian runaway selection. Here, we explore the costs and benefits of long sperm and SR genotypes, both in the sex that carries them and in the sex that does not. We measured male and female fitness in inbred lines of D. melanogaster derived from four populations previously selected for long sperm, short sperm, long SRs, or short SRs. We specifically asked: what are the costs and benefits of long sperm in males and long SRs in females? Furthermore, do genotypes that generate long sperm in males or long SRs in females impose a fitness cost on the opposite sex? Answers to these questions will address whether long sperm are an honest indicator of male fitness, if male post-...在果蝇（Drosophila）中，基于雌性初级精子储存器官——受精囊（seminal receptacle, SR）的长度，长精子在精子竞争中更具优势。这种精子与受精囊的相互作用，加之相关性状间的遗传相关，提示过长精子与受精囊长度的协同进化可能由费舍尔失控选择（Fisherian runaway selection）驱动。本研究旨在探究长精子与长受精囊基因型的成本与收益，分别在携带该性状的性别与不携带该性状的性别中展开分析。我们以源自四个此前分别针对长精子、短精子、长受精囊及短受精囊进行选育的种群的黑腹果蝇（D. melanogaster）近交系为实验材料，测定雌雄个体的适合度。我们具体提出以下两个问题：其一，雄性长精子与雌性长受精囊各自存在哪些成本与收益？其二，能够使雄性产生长精子或使雌性拥有长受精囊的基因型，是否会对异性的适合度造成代价？上述问题的答案将阐明长精子是否为雄性适合度的诚实指示信号，以及雄性交配后（male post-）的相关议题。