Data from: Evolution of carotenoid pigmentation in caciques and meadowlarks (Icteridae): repeated gains of red plumage coloration by carotenoid C4-oxygenation

Many animals use carotenoid pigments to produce yellow, orange, and red coloration. In birds, at least 10 carotenoid compounds have been documented in red feathers; most of these are produced through metabolic modification of dietary precursor compounds. However, it is poorly understood how lineages have evolved the biochemical mechanisms for producing red coloration. We used high-performance liquid chromatography to identify the carotenoid compounds present in feathers from 15 species across two clades of blackbirds (the meadowlarks and allies, and the caciques and oropendolas; Icteridae), and mapped their presence or absence on a phylogeny. We found that the red plumage found in meadowlarks includes different carotenoid compounds than the red plumage found in caciques, indicating that these gains of red color are convergent. In contrast, we found that red coloration in two closely related lineages of caciques evolved twice by what appear to be similar biochemical mechanisms. The C4-oxygenation of dietary carotenoids was responsible for each observed transition from yellow to red plumage coloration, and has been commonly reported by other researchers. This suggests that the C4-oxygenation pathway may be a readily evolvable means to gain red coloration using carotenoids.

诸多动物均利用类胡萝卜素（carotenoid）色素来生成黄色、橙色与红色体色。在鸟类中，研究人员已在红色羽毛中记录到至少10种类胡萝卜素化合物，其中多数通过对膳食前体化合物进行代谢修饰而生成。然而学界对各演化支如何演化出生成红色体色的生化机制仍知之甚少。本研究采用高效液相色谱（high-performance liquid chromatography）技术，对拟鹂科（Icteridae）两个黑鹂演化支下的15个物种的羽毛所含类胡萝卜素化合物进行了鉴定——这两个演化支分别为草地鹨类及其近缘类群、拟椋鸟与大尾拟椋鸟，并将各类化合物的存在与否映射至系统发育树之上。研究发现，草地鹨类的红色羽毛与拟椋鸟的红色羽毛所含类胡萝卜素化合物存在差异，这表明二者的红色体色演化属于趋同演化。与之相反，本研究发现，两个亲缘关系密切的拟椋鸟演化支分别独立演化出了红色体色，且二者所采用的生化机制似乎高度相似。膳食类胡萝卜素的C4位氧合作用，是所有观测到的黄色羽毛向红色羽毛转变的核心机制，且该机制已被其他研究者广泛报道。这表明C4位氧合通路或许是一种易于演化获得的、利用类胡萝卜素生成红色体色的途径。