“The new news is that organisms can shape their own evolution by changing their environment.”

Guppies are a low maintenance pet for many.

But, they have recently helped a UC Riverside scientist explore an important question about evolution:

A team of scientists traveled to Trinidad, and, in a guppies’ native habitat, conducted an experiment: They moved guppies from areas in streams where predators were plentiful to areas where predators were mostly absent. Guppies were marked so they could be tracked.

Over the course of four years, they studied how the relocated guppies changed in comparison to ones from the original spots.

The scientists tracked the males, which tend to live about five months. They looked at key traits affecting population growth—the age and size at maturity of the fish.

They also recorded how the environment changed as the guppy populations expanded, focusing on the abundance of food such as algae and insects, as well as the presence of other non predator fish.

They found a two-to-three-year lag between when guppies were introduced and when males evolved, suggesting that the guppies were first changing their new environments, and then, as a result, changing themselves.

David Reznick, a professor of biology and co-author of a paper on the research, which has been published in American Naturalist, explained that, in the wild, guppies can migrate over waterfalls and rapids to places where most predators can’t follow them. Once they arrive in safer terrain, they evolve rapidly, becoming genetically distinct from their ancestors.

“The speed of evolution makes it possible to study how it happens,” Reznick said. “The new news is that organisms can shape their own evolution by changing their environment.”

Reznick’s is now looking at applying these concepts to questions about human evolution.

“Unlike guppies and other organisms, human population density seems to increase without apparent limit, which increases our impact on our environment and on ourselves,” he said.

Co-authors on the study included Ron Basser, a former doctoral student at UC Riverside and now assistant professor at Williams College; Joe Travis at Florida State University; Corey Handelsman, Cameron Ghalambor, Emily Ruell, and Julian Torres-Dowdall from Colorado State University; Tim Coulson and Tomos Potter of Oxford University, and Paul Bentzen of Dalhousie University in Canada.

Source: Press release by Jules Bernstein

Featured image: Guppies swim near the Quare River in Trinidad, where conditions are right for observation with and without predators. (David Reznick/UCR)