From ScienceDaily :
A study of one of the world’s largest and most colorful bird families has dispelled a long-held notion, first proposed by Charles Darwin, that animals are limited in their options to evolve showiness. The study – the largest of its kind – was published today in the Proceedings of the Royal Society B.
According to the theory,
“Animals have limited resources, and they have to spend those in order to develop showy plumage or precision singing that help them attract mates and defend territories,” said Nick Mason, the paper’s lead author. “So it seems to make sense that you can’t have both. But our study took a more detailed look and suggests that actually, some species can.” Mason did the research as a master’s student at San Diego State University. He is now a Ph.D. student at the Cornell Lab of Ornithology.
Mason and his colleagues tested the idea of trade-offs by looking at a very large family of songbirds from Central and South America, the tanagers. This group consists of 371 species – nearly 10 percent of all songbirds. It includes some of the most spectacularly colorful birds in the world such as the Paradise Tanager as well as more drab birds such the Black-bellied Seedeater. The group also includes both accomplished and weak songsters alike.
And guess what?
The study puts a significant dent in the idea of evolutionary trade-offs between plumage and song. It’s still possible that trade-offs take place at the level of genus, Mason said, or that they influence species relatively fleetingly as evolutionary pressures appear and disappear. But as a broad effect on an entire family of birds, a voice–plumage tradeoff doesn’t seem to exist. One possibility is that the resources needed to develop fancy plumage are different from the ones required for complex songs, freeing tanagers to invest in both forms of showiness simultaneously.
Another possibility is that continuing to rely on Darwin and his followers for insights is a good way to get it wrong.
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