What the vibrant pigments of bird feathers can teach us about how the evolution works

A research team led by the University of Arizona has shown that evolution depends on the interaction of species within a community.

All living things exist in communities, where they depend on resources or services provided by other species. As members of the community change, the products that the species depend on and share with each other do the same. The late George Gaylord Simpson, professor of geoscience at the AU and one of the most influential thinkers of the last century 's evolution, has proposed that these fluctuating dependencies determine the speed of life. evolution.

It is notoriously difficult to test this theory because the interactions between species are both ubiquitous and ephemeral, said Alexander Badyaev, professor of ecology and evolutionary biology at UA. But he and his team believe they have found a solution by examining the evolution of biochemical pathways that produce color diversity in birds.

Badyaev and his co-authors have shown that the way in which biochemical processes are structured in birds is the key to understanding how species gain and lose their dependence on others in their communities. As a result, it determines how quickly species can diversify and evolve.

The new study, published in Nature Communications Earlier this month, both confirm this prediction and reveal the mechanisms that show how it works.

Badyaev has studied the evolution of the pathways by which birds convert food carotenoids into molecules necessary for everything from vision to the immune system to the pigmentation of feathers.

The team, which included undergraduate and graduate students and a postdoctoral fellow in Badyaev's lab, constructed and tested the structure of thousands of biochemical pathways of carotenoids in nearly 300 species of birds. . They then explored the evolution of trajectories over the last 50 million years.

"The importance of carotenoids for multiple functions contrasts with the inability of birds to create carotenoids themselves," said Mr Badyaev. "Thus, a species pulling its food carotenoids from a single food source is hostage to the disappearance of that source."

The solution lies in the structure of biochemical pathways, where the same molecules could be produced interchangeably by different dietary carotenoids. This not only allows the species to reliably receive their essential carotenoids despite the fluctuations of the environment, it also allows the birds to explore additional biochemical pathways. Badyaev calls this "the control of internalization".

"Think of hanging a rope over a cliff.With a rope, if it disappears, you will die.If you have two and one fails, you will live.But a third safety rope allows a sufficient stability to be able to distinguish something from the first two – like a ladder – and thus take control of your trajectory while stability lasts, "said Badyaev.

His team found that when species temporarily integrate control of their carotenoid production by capitalizing on multiple sources of carotenoids, they evolve at exceptionally high rates and produce some of the most extravagant birds in the world.

"But by the time you do that, you become susceptible to new external controls, and then the cycle repeats itself," he said. "It's because the gains and losses of external controls occur at an equal frequency."

This research supports both Darwin's theory of evolution by natural selection and Simpson's idea that the evolution of an organism depends on other members. of his community.

"It shows how much adaptation and evolutionary change are mechanically linked," Badyaev said. "This shows why winning and losing internal control is a key part of the evolution."