Lizard Study Analyzes Importance Of The Founder Effect
February 3, 2012

Lizard Study Analyzes Importance Of The Founder Effect

A team of American researchers have reportedly completed what they are calling the first experimental study of the phenomenon known as the founder effect -- the loss of genetic variation that occurs when a new population is established created using a small group from a larger existing population -- in a natural setting.

The researchers, whose work was published online Friday in Science Express and is scheduled to appear in the print journal Science on February 17, "had an unprecedented opportunity to address a long-simmering controversy in evolutionary biology," the University of California-Davis (UC Davis) said in a press release Thursday.

That controversy stems from the perceived importance of the founder effect when it comes to a species evolution, the university said. Some scientists believe that the phenomenon is "pivotally important" in how a group of animals evolves, while others refer to is as a "bit player on the evolutionary stage," and that natural selection plays a far more important role than the loss of genetic variation.

Thomas Schoener, a professor of evolution and ecology at UC Davis, and colleagues from Harvard University, Duke University, and the University of Rhode Island (URI), began their work after Hurricane Frances washed over seven small islands in the Caribbean, near Great Abaco, Bahamas, in September 2004. Prior to the hurricane, those islands were home to the brown anole (Anolis sagrei), but afterwards, the populations were wiped out without a trace.

The following May, Schoener and his team randomly selected one male and one female brown anole that had been living on a larger island nearby, then placed them on the seven smaller islands in an attempt to create new populations of the lizard species to replace those wiped out by Frances. Over a four year span, they studied the lizards, and found that they both adapted to their new homes, but also maintained characteristics of old.

"For instance, lizard limb length correlates with the average diameter of vegetation on an island. Because the founder islands had smaller vegetation than the source island, the length of lizard limbs decreased, as expected, due to natural selection," the UC Davis press release said. "But islands containing lizards with the largest limbs at the beginning of the study still had the lizards with the longest limbs at the end of the study."

Ultimately, the researchers discerned that both the founder effect and natural selection played roughly equal roles in the evolution of the brown anole species.

"Our study is an entirely unique approach to a question of longstanding importance for evolutionary biology regarding the founder effect: Will it persist in the face of the strong selection that would often exist in the colonized environment?" Schoener said in a statement. "The answer we found is that founder effects can leave a persistent signal as generations replace one another over time, even as populations adapt to new conditions. Our study of these fundamental evolutionary principles affects our general understanding of how the biological world works."

In a separate statement, Jason Kolbe, a URI assistant professor of biological sciences, said that the landmark study was "the first to study this process experimentally in a natural setting," and that as a result he and his colleagues "were able to account for multiple evolutionary mechanisms through time“¦ We manipulated the founding of these islands, but everything else about it was natural."

The founder effect was originally outlined in full by evolutionary biologist Ernst Mayr in 1942. This latest study was funded by the National Science Foundation (NSF) and the National Geographic Society.


Image Caption: These Caribbean brown anole lizards were part of a UC Davis study of the founder effect--a long-simmering controversy in evolutionary biology. (Manuel Leal/Duke University)


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