A melanin-based trait is more strongly related to body size in the tropics than in temperate regions in the globally distributed barn owl family

Life history traits differ between organisms living in the tropics, northern and southern hemispheres, and sexual selection is thought to be stronger close to the equator than in temperate regions. Although birds are often supposed to be more brightly coloured in the tropics, the current evidence of geographic variation in the intensity of sexual selection and sex-specific natural selection is equivocal. Whether sex-specific traits signal aspects of individual quality better in the tropics than in the temperate regions of the northern and southern hemispheres therefore remains an open question. We examined predictions of this hypothesis in the Tytonidae family (barn owls and their relatives) because females, on average, display larger black spots on the tip of their ventral body feathers than males, and this trait is associated with aspects of individual quality. We measured the size of melanic spots and the wing length of 7893 Tytonidae skins collected worldwide and preserved in natura...

生活史特征在热带、南北半球的生物类群间存在显著差异，且学界普遍认为赤道附近的性选择强度高于温带区域。尽管人们通常认为热带地区的鸟类体色更为艳丽，但目前关于性选择强度以及性别特异性自然选择的地理变异的相关证据仍尚无定论。因此，相较于南北半球的温带地区，热带地区的性别特异性性状是否能更有效地表征个体质量的相关特征，仍是一个悬而未决的科学问题。本研究以草鸮科（Tytonidae，即仓鸮及其近缘类群）为研究对象，对该假说的相关预测进行验证，原因在于该类群雌性腹羽尖端的黑色斑点平均尺寸大于雄性，且这一性状与个体质量的多个方面存在关联。我们测量了全球范围内采集、经原生保存的7893份草鸮科标本的黑素斑点尺寸与翅长……