Plant study hints evolution may be predictable
Similar leaf types evolved independently in three species of plants found in cloud forests of Oaxaca, Mexico and three species of plants in similar environment in Chiapas, Mexico. This example of parallel evolution is one of several found by Yale-led scientists and suggests that evolution may be predictable. Credit: Yale University

Evolution has been seen as a random process with the traits of species shaped by chance and environmental events.

An international team of scientists led by researchers from Yale University and Columbia University have found that a particular plant has evolved three different leaf types over and over again in mountainous regions.

The first examples of plants of a phenomenon known as "replicated radiation" were provided by the findings, suggesting that evolution is not always random but can be predicted.

The study is in a journal.

"The findings show how predictable evolution can be, with organisms developing and natural selection producing the same forms again and again under certain circumstances," said Donoghue. Evolutionary biology may become more of a predictive science than we thought.

The research team studied the genetics of the plant that spread from Mexico into Central and South America around 10 million years ago. The same plant group was studied by Donoghue for his PhD. He was in favor of an alternative theory in which large, hair-covered leaves and small smooth leaves evolved early in the evolution of the group and then both forms migrated separately, being dispersed by birds.

In each of the mountain regions, the two different leaf types evolved in parallel.

Donoghue said that he came to the wrong conclusion because he didn't have the relevant data back in the 70s.

A very similar set of leaf types were found in 9 regions. There are places where the full array of leaf types have yet to evolve. In the cloud forest of Mexico, Central America, and northern South America, the large hairy leaf types are hard to find.

According to Donoghue, the large, hairy leaf form of the plants will eventually evolve in the country.

The Anolis lizards are found in the Caribbean. The same set of body forms evolved on different islands. Evolutionary biologists will try to find the general circumstances under which they can make predictions about evolutionary trajectory.

Ericka Edwards, professor of ecology and evolutionary biology at Yale and co-corresponding author of the paper, said that the work has revealed a new system to study evolutionary adaptation. The next challenge is to better understand the functional significance of these leaf types and the underlying genetic architecture that enables their repeated emergence.

The authors are from Columbia.

More information: Michael J. Donoghue et al, Replicated radiation of a plant clade along a cloud forest archipelago, Nature Ecology & Evolution (2022). DOI: 10.1038/s41559-022-01823-x Journal information: Nature Ecology & Evolution