Data from: Female control over multiple matings increases the opportunity for postcopulatory sexual selection

It is widely acknowledged that in most species sexual selection continues after mating. Although it is generally accepted that females play an important role in generating paternity biases (i.e., cryptic female choice), we lack a quantitative understanding of the relative importance of female-controlled processes in influencing variance in male reproductive fitness. Here we address this question experimentally using the guppy Poecilia reticulata, a polyandrous fish in which pre- and postcopulatory sexual selection jointly determine male reproductive fitness. We used a paired design to quantify patterns of paternity for pairs of rival males across two mating contexts, one in which the female retained full control over double (natural) matings and one where sperm from the same two males were artificially inseminated into the female. We then compared the relative paternity share for a given pair of males across both contexts, enabling us to test the key prediction that patterns of paternity will depend on the extent to which females retain behavioural control over matings. As predicted, we found stronger paternity biases when females retained full control over mating compared to when artificial insemination was used. Concomitantly, we show that the opportunity for postcopulatory sexual selection (standardised variance in male reproductive success) was greater when females retained control over double matings compared to when artificial insemination was used. Finally, we show that the paternity success of individual males exhibited higher repeatability across successive brood cycles when females retained behavioural control of matings compared to when AI was used. Collectively, these findings underscore the critical role that females play in determining the outcome of sexual selection and to our knowledge provide the first experimental evidence that behaviourally moderated components of cryptic female choice increase the opportunity for sexual selection.学界普遍认为，多数物种的性选择（sexual selection）会在交配完成后持续进行。尽管人们普遍认可雌性在产生父权偏差（paternity biases，即隐秘雌性选择（cryptic female choice））中发挥着重要作用，但目前仍缺乏对雌性调控过程影响雄性繁殖适合度（reproductive fitness）差异的相对重要性的定量认知。本研究以孔雀鱼（Poecilia reticulata）为实验对象，通过实验手段探讨该问题。该物种为实行一妻多夫制的鱼类，其交配前与交配后的性选择共同决定雄性的繁殖适合度。我们采用配对实验设计，在两种交配情境下量化了竞争性雄性的父权分配模式：一种情境下雌性对两次自然交配拥有完全自主控制权，另一种情境下则将来自同一对雄性的精子人工授精（artificial insemination，下文简称AI）至雌性体内。随后我们比较了给定雄性对在两种情境下的相对父权占比，借此得以检验核心预测：父权模式将取决于雌性对交配行为的保留控制权程度。正如预测所示，相较于人工授精（AI）情境，当雌性完全掌控交配过程时，父权偏差更为显著。与此同时，我们发现，相较于人工授精（AI）情境，当雌性保留两次交配的控制权时，交配后性选择的机会（即雄性繁殖成功的标准化方差）更高。最后我们证实，相较于人工授精（AI）情境，当雌性掌控交配行为时，单个雄性的父权成功率在连续多胎繁殖周期中表现出更高的重复性。综上，这些研究结果凸显了雌性在决定性选择结果中的关键作用；据我们所知，本研究首次通过实验证实，受行为调控的隐秘雌性选择组分可提升性选择的机会。