Chapman Nadine C, Siriwat Penthai, Howie James, Towlson Aaron, Bellamy Lawrence, Fowler Kevin, Pomiankowski Andrew
Department of Genetics, Evolution and Environment University College London London UK.
School of Life and Environmental Science University of Sydney Sydney NSW Australia.
Ecol Evol. 2017 Jul 18;7(17):6659-6668. doi: 10.1002/ece3.3225. eCollection 2017 Sep.
All too often, studies of sexual selection focus exclusively on the responses in one sex, on single traits, typically those that are exaggerated and strongly sexually dimorphic. They ignore a range of less obvious traits and behavior, in both sexes, involved in the interactions leading to mate choice. To remedy this imbalance, we analyze a textbook example of sexual selection in the stalk-eyed fly (). We studied several traits in a novel, insightful, and efficient experimental design, examining 2,400 male-female pairs in a "round-robin" array, where each female was tested against multiple males and vice versa. In , females exhibit strong mate preference for males with highly exaggerated eyespan, and so we deliberately constrained variation in male eyespan to reveal the importance of other traits. Males performing more precopulatory behavior were more likely to attempt to mate with females and be accepted by them. However, behavior was not a necessary part of courtship, as it was absent from over almost half the interactions. Males with larger reproductive organs (testes and accessory glands) did not make more mating attempts, but there was a strong tendency for females to accept mating attempts from such males. How females detect differences in male reproductive organ size remains unclear. In addition, females with larger eyespan, an indicator of size and fecundity, attracted more mating attempts from males, but this trait did not alter female acceptance. Genetic variation among males had a strong influence on male mating attempts and female acceptance, both via the traits we studied and other unmeasured attributes. These findings demonstrate the importance of assaying multiple traits in males and females, rather than focusing solely on prominent and exaggerated sexually dimorphic traits. The approach allows a more complete understanding of the complex mating decisions made by both males and females.
性选择的研究常常只专注于某一性别的反应、单一性状，通常是那些夸张且具有强烈两性异形的性状。它们忽视了两性中一系列不太明显的性状和行为，这些性状和行为参与了导致配偶选择的互动过程。为了纠正这种不平衡，我们分析了一个关于茎眼蝇性选择的典型案例。我们采用了一种新颖、有见地且高效的实验设计来研究多个性状，以“循环赛”的方式对2400对雌雄进行了测试，即每只雌性与多只雄性进行测试，反之亦然。在茎眼蝇中，雌性对眼间距极度夸张的雄性表现出强烈的配偶偏好，因此我们特意限制雄性眼间距的变化，以揭示其他性状的重要性。进行更多交配前行为的雄性更有可能试图与雌性交配并被雌性接受。然而，行为并非求爱的必要组成部分，因为在几乎一半以上的互动中都没有出现这种行为。生殖器官（睾丸和附属腺）较大的雄性并没有进行更多的交配尝试，但雌性有强烈的倾向接受这类雄性的交配尝试。雌性如何检测雄性生殖器官大小的差异仍不清楚。此外，眼间距较大的雌性，这是体型和繁殖力的一个指标，吸引了雄性更多的交配尝试，但这个性状并没有改变雌性的接受度。雄性之间的遗传变异对雄性的交配尝试和雌性的接受度都有很大影响，这既通过我们研究的性状，也通过其他未测量的属性。这些发现表明，对雄性和雌性的多个性状进行分析很重要，而不是只关注突出且夸张的两性异形性状。这种方法能让我们更全面地理解雄性和雌性做出的复杂交配决策。
