Study Co-Written by UT Professor Finds Florida Lizards Evolve Rapidly, Within 15 Years and 20 Generations

Scientists working on islands in Florida have documented the rapid evolution of a native lizard species — in as little as 15 years — as a result of pressure from an invading lizard species, introduced from Cuba.

After contact with the invasive species, the native lizards began perching higher in trees, and, generation after generation, their feet evolved to become better at gripping the thinner, smoother branches found higher up.

The change occurred at an astonishing pace: within a few months, native lizards had begun shifting to higher perches, and over the course of 15 years and 20 generations, their toe pads had become larger, with more sticky scales on their feet.

“When I started this project in 1994, I was merely looking at ecological effects of the invasive lizard on the native lizard — the perch shift. I had no idea that only 20 years later we would demonstrate evolution in the native lizard, and I feel lucky to have been part of this awesome team,” said Todd Campbell, an associate professor of biology at The University of Tampa and one of the lead authors of the study appearing in the Oct. 24 edition of the journal Science.

According to the research team, to put this shift in perspective, if human height were evolving as fast as these lizards' toes, the height of an average American man would increase from about 5 foot, 9 inches today to about 6 foot, 4 inches within 20 generations — an increase that would make the average U.S. male the height of an NBA shooting guard.

"Although humans live longer than lizards, this rate of change would still be rapid in evolutionary terms," the researchers said.

The native lizards studied, known as Carolina anoles or green anoles, are common in the southeastern U.S. The invasive species, Cuban anoles or brown anoles, are native to Cuba and the Bahamas. Brown anoles first appeared in South Florida in the 1950s, possibly as stowaways in agricultural shipments from Cuba, and have since spread across the southeastern U.S. and have even jumped to Hawaii.

Campbell began studying the effect of the brown anole on the green anole in 1994 for his doctoral dissertation research at the University of Tennessee, and continued studying them after joining the faculty at The University of Tampa in 2003.

This latest study is one of only a few well-documented examples of what evolutionary biologists call "character displacement," in which similar species competing with each other evolve differences to take advantage of different ecological niches. A classic example comes from the finches studied by Charles Darwin. Two species of finch in the Galápagos Islands diverged in beak shape as they adapted to different food sources.

“We have long known that adaptation to novel environmental conditions can proceed at a fast pace, but only a few studies have revealed adaptive evolution in response to competition with other species, so this is a proud moment for all of us,” Campbell said.

The researchers speculate that the competition between brown and green anoles for the same food and space may be driving the adaptations of the green anoles.

Other co-authors of the study include Yoel Stuart of The University of Texas at Austin; Paul Hohenlohe of the University of Idaho; Robert Reynolds and Liam Revell of the University of Massachusetts, Boston; and Jonathan Losos at Harvard University.

Support for this research was provided by the National Science Foundation, the National Institutes of Health, The University of Tennessee, Knoxville, The University of Tampa and the Museum of Comparative Zoology at Harvard University.