Data from: Micropyle number is associated with elevated female promiscuity in Lepidoptera

In the majority of insects, sperm fertilise the egg via a narrow canal through the outer chorion called the micropyle. Despite having this one primary function, there is considerable unexplained variation in the location, arrangement and number of micropyles within and between species. Here, we examined the relationship between micropyle number and female mating pattern through a comparative analysis across Lepidoptera. Three functional hypotheses could explain profound micropylar variation: (i) increasing micropyle number reduces the risk of infertility through sperm limitation in species that mate infrequently; (ii) decreasing micropyle number reduces the risk of pathological polyspermy in species that mate more frequently; (iii) increasing micropyle number allows females to exert greater control over fertilisation within the context of post-copulatory sexual selection, which will be more intense in promiscuous species. Micropyle number was positively related to the degree of female promiscuity as measured by spermatophore count, regardless of phylogenetic signal, supporting the hypothesis that micropyle number is shaped by post-copulatory sexual selection. We discuss this finding in the context of cryptic female choice, sperm limitation and physiological polyspermy.

在绝大多数昆虫中，精子会通过穿过外层卵壳（chorion）的狭窄通道——精孔（micropyle）——完成对卵子的受精。尽管精孔仅承担这一项核心功能，但在物种内部及不同物种之间，精孔的位置、排布与数量仍存在大量尚无合理解释的变异。本研究通过对鳞翅目（Lepidoptera）类群的比较分析，探究了精孔数量与雌性交配模式之间的关联。有三项功能性假说可解释精孔数量的显著变异：（1）在交配频率较低的物种中，增加精孔数量可通过缓解精子限制降低不育风险；（2）在交配更为频繁的物种中，减少精孔数量可降低病理性多精受精的风险；（3）在混交程度更高的类群中，交配后性选择（post-copulatory sexual selection）的作用更强，增加精孔数量可使雌性在该情境下对受精过程实现更强的调控。无论系统发育信号（phylogenetic signal）影响如何，精孔数量与通过精荚（spermatophore）计数所衡量的雌性混交程度均呈正相关，这一结果支持了精孔数量由交配后性选择塑造的假说。本研究还结合隐秘雌性选择（cryptic female choice）、精子限制与生理性多精受精等情境，对上述发现展开了讨论。