From: ENN Staff
Published December 12, 2013 12:30 PM

Rodent Study Questions Common Understanding of Evolution

According to new research, studying the rodent family tree can shed some light on how species evolve after they move into a new area.

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Conducted in part by researchers at Florida State University, the study of the evolutionary history of rodents calls into doubt a generally held understanding that when a species colonizes a new region, evolution leads to a dramatic increase in the number and variety of species.

"Biological diversification, or adaptive radiation, is generally thought to be the major explanation for diversification across all of life," said Scott J. Steppan, a Florida State University professor of biological science. "One of the most fundamental questions in biology is why some groups of plants and animals have lots of species and others do not. To address this question, we developed the most comprehensive DNA-based family tree of the most evolutionally successful group of mammals — the muroid rodents."

In the study, "Ecological Opportunity and Incumbency in the Diversification of Repeated Continental Colonizations by Muroid Rodents," researchers used the phylogeny, or evolutionary family tree, of these rodents to test whether the adaptive radiation model of biological diversification actually is as common as presumed.

As part of the study, the researchers demonstrated that muroids have colonized continents at least 28 times. Muroids include most of the species used in biomedical research, such as mice, rats, hamsters and gerbils.

When a species first colonizes a new area with no close competitors, biologists would expect the rate at which new species are created to increase rapidly. Then, adaptation into new niches should make the descendent species very different from one another. Finally, as niches fill up, these first two processes should slow down.

"In this study, we discovered that contrary to expectations, colonizing even entire continents does not generally lead to a rapid adaptive radiation, thus calling into question this model as a general explanation about the diversity of life on Earth," Steppan said.

The study is published in the journal Systematic Biology.

Read more at Florida State University.

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