Department of Behavioural Ecology and Evolutionary Genetics, Max Planck Institute for Ornithology, Seewiesen, Germany.
J Evol Biol. 2023 May;36(5):764-779. doi: 10.1111/jeb.14172. Epub 2023 Mar 27.
Differences in the strength of sexual selection between males and females can lead to sexual dimorphism. Extra-pair paternity (EPP) can increase the variance in male reproductive success and hence the opportunity for sexual selection. Previous research on birds suggests that EPP drives the evolution of dimorphism in plumage colour and in body size. Because EPP increases the intensity of sexual selection in males, it should lead to increased dimorphism in species with larger or more colourful males, but decreased dimorphism in species with larger or more colourful females. We explored the covariation between EPP and sexual dimorphism in wing length and plumage colouration in 401 bird species, while controlling for other, potentially confounding variables. Wing length dimorphism was associated positively with the frequency of EPP, but also with social polygamy, sex bias in parental behaviour and body size and negatively with migration distance. The frequency of EPP was the only predictor of plumage colour dimorphism. In support of our prediction, high EPP levels were associated with sexual dichromatism, positively in species in which males are more colourful and negatively in those in which females are more colourful. Contrary to our prediction, high EPP rates were associated with increased wing length dimorphism in species with both male- and female-biased dimorphism. The results support a role for EPP in the evolution of both size and plumage colour dimorphism. The two forms of dimorphism were weakly correlated and predicted by different reproductive, social and life-history traits, suggesting an independent evolution.
雄性和雌性之间的性选择强度的差异会导致性二态性。 配偶外交配（EPP）可以增加雄性生殖成功的方差，从而为性选择提供机会。 先前对鸟类的研究表明，EPP 推动了羽毛颜色和体型的性二态性进化。 因为 EPP 增加了雄性的性选择强度，所以它应该导致具有更大或更鲜艳颜色的雄性物种的二态性增加，而具有更大或更鲜艳颜色的雌性物种的二态性减少。 我们通过控制其他潜在的混杂变量，探索了 401 种鸟类中翼长和羽毛颜色性二态性与 EPP 之间的共变关系。 翼长二态性与 EPP 的频率呈正相关，但也与社会多配偶制、亲代行为的性别偏向以及体型呈负相关，与迁徙距离呈负相关。 EPP 的频率是羽毛颜色二态性的唯一预测因子。 支持我们的预测，EPP 水平高与性二色性有关，在雄性颜色更鲜艳的物种中呈正相关，在雌性颜色更鲜艳的物种中呈负相关。 与我们的预测相反，EPP 率高与具有雄性和雌性偏向的二态性的物种的翼长二态性增加有关。 结果支持 EPP 在大小和羽毛颜色二态性进化中的作用。 两种二态性之间相关性较弱，并且由不同的生殖、社会和生活史特征预测，表明它们的进化是独立的。
