Lab of Ornithology postdoc (and first author) Rusty Ligon and grad student Nick Mason are part of a team that just published a neat paper on the evolution of plumage coloration among finches: Ligon, R. A., Simpson, R. K., Mason, N. A., Hill, G. E., & McGraw, K. J. (2016). Evolutionary innovation and diversification of carotenoid-based pigmentation in finches. Evolution. http://doi.org/10.1111/evo.13093
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.