Cardoso Gonçalo C, Mota Paulo G
Am Nat. 2022 Dec;200(6):E237-E247. doi: 10.1086/721371. Epub 2022 Oct 7.
AbstractSexual ornamentation is often assumed to be costly, allowing honest signaling of individual quality, and carotenoid-based colors have been proposed to bear significant costs. If carotenoid-based colors are costly to produce, sexually selected signals should use more concentrated carotenoid pigments and have more saturated color than nonsexual signals, where honesty-guaranteeing costs are not required. We tested this prediction comparing carotenoid-based colors across canaries, goldfinches, and allies because many of these species use yellow plumage as sexual ornamentation but also have yellow rumps that appear to be nonsexual flash marks. Only in the breast, but not the rump, was there an asymmetric codistribution of male and female color saturation, with males similarly or more saturated than females, indicating evolution of breast color by sexual selection. Yellow was not consistently more saturated in the breast than in the rump, and the codistribution of rump and breast color saturation indicated that saturated rumps can persist irrespective of breast color. This challenges the assumption that carotenoid-based colors bear significant costs. The use of carotenoid coloration as sexual signals in this clade may instead be due to social costs, cost-free index mechanisms for signaling quality, and/or socially monogamous species evolving low-cost signals to mostly discriminate against the lowest-quality mates.
摘要
性装饰通常被认为是有代价的，能够诚实地表明个体质量，并且基于类胡萝卜素的颜色被认为具有显著代价。如果基于类胡萝卜素的颜色生产成本高昂，那么性选择信号应该比非性信号使用更浓缩的类胡萝卜素色素，且颜色更饱和，因为非性信号不需要保证诚实的代价。我们通过比较金丝雀、金翅雀及相关物种中基于类胡萝卜素的颜色来验证这一预测，因为这些物种中的许多都将黄色羽毛用作性装饰，但它们也有黄色的臀部，这似乎是非性的闪光标记。只有在胸部而非臀部，雄性和雌性的颜色饱和度存在不对称的共分布，雄性的饱和度与雌性相似或更高，这表明胸部颜色是通过性选择进化而来的。黄色在胸部并不总是比在臀部更饱和，臀部和胸部颜色饱和度的共分布表明，无论胸部颜色如何，饱和的臀部都可能持续存在。这挑战了基于类胡萝卜素的颜色具有显著代价这一假设。在这个进化枝中，将类胡萝卜素着色用作性信号，可能反而归因于社会代价、用于表明质量的无成本指标机制，和/或实行社会一夫一妻制的物种进化出低成本信号以主要区分最低质量的配偶。
