Ligon Russell A, Simpson Richard K, Mason Nicholas A, Hill Geoffrey E, McGraw Kevin J
School of Life Sciences, Arizona State University, Tempe, Arizona, 85287.
Laboratory of Ornithology, Cornell University, Ithaca, New York, 14850.
Evolution. 2016 Dec;70(12):2839-2852. doi: 10.1111/evo.13093. Epub 2016 Nov 7.
The ornaments used by animals to mediate social interactions are diverse, and by reconstructing their evolutionary pathways we can gain new insights into the mechanisms underlying ornamental innovation and variability. Here, we examine variation in plumage carotenoids among the true finches (Aves: Fringillidae) using biochemical and comparative phylogenetic analyses to reconstruct the evolutionary history of carotenoid states and evaluate competing models of carotenoid evolution. Our comparative analyses reveal that the most likely ancestor of finches used dietary carotenoids as yellow plumage colorants, and that the ability to metabolically modify dietary carotenoids into more complex pigments arose secondarily once finches began to use modified carotenoids to create red plumage. Following the evolutionary "innovation" that enabled modified red carotenoid pigments to be deposited as plumage colorants, many finch species subsequently modified carotenoid biochemical pathways to create yellow plumage. However, no reversions to dietary carotenoids were observed. The finding that ornaments and their underlying mechanisms may be operating under different selection regimes-where ornamental trait colors undergo frequent reversions (e.g., between red and yellow plumage) while carotenoid metabolization mechanisms are more conserved-supports a growing empirical framework suggesting different evolutionary patterns for ornaments and the mechanistic innovations that facilitate their diversification.
动物用于调节社会互动的装饰物多种多样，通过重建其进化路径，我们可以对装饰创新和变异性背后的机制有新的认识。在这里，我们使用生化和比较系统发育分析来研究雀科（鸟类：雀科）羽毛类胡萝卜素的变异，以重建类胡萝卜素状态的进化历史，并评估类胡萝卜素进化的竞争模型。我们的比较分析表明，雀科最可能的祖先将膳食类胡萝卜素用作黄色羽毛的着色剂，并且一旦雀科开始使用经过修饰的类胡萝卜素产生红色羽毛，将膳食类胡萝卜素代谢修饰成更复杂色素的能力便随之出现。在进化“创新”使经过修饰的红色类胡萝卜素色素能够作为羽毛着色剂沉积之后，许多雀科物种随后改变了类胡萝卜素生化途径以产生黄色羽毛。然而，未观察到向膳食类胡萝卜素的逆转。装饰物及其潜在机制可能在不同的选择机制下运作——装饰性状颜色频繁逆转（例如，在红色和黄色羽毛之间），而类胡萝卜素代谢机制更保守——这一发现支持了一个不断发展的实证框架，该框架表明装饰物和促进其多样化的机制创新具有不同的进化模式。
