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frojack writes:

Article from The Scientist:

With a name straight out of a horror movie, The Spoil Islands in the Mosquito Lagoon off the coast of Florida, a by-product of dredging in the area to make the Intra-coastal Waterway in the 1950s, served as the prime site for an experimental evolution study.

By the 1990s, flora and fauna from the mainland—including the Carolina anole (Anolis carolinensis), a small arboreal lizard—had colonized the islands.

In May 1995, Yoel Stuart of the University of Texas and Todd Campbell, of from the University of Tampa, chose six islands with resident populations of the Carolina anole and recorded the height at which the lizards were perched. He then introduced small populations of the Brown anole (Anolis sagrei)—native to Cuba and the Bahamas to three of the islands, leaving the other three islands undisturbed.

This wasn't the first place where these lizard species have met. In other shared habitats, it was found that the Carolina anole was always found much higher in the trees, had larger adhesive toepads because they have more lamellae, grooves that allow the digits to stick better to surfaces.

The researchers wanted to see if the same adaptations would result due to competitive pressure, and if so how long it might take.

Sure enough, the brown anole populations grew rapidly, and after just three months, the Carolina anoles began perching at greater heights. On the control islands, however, the Carolina anole was making full use of its typical habitat: the entire tree, from the ground to the crown.

That wasn't the surprising part. Such results could be explained by phenotypic plasticity, the ability of an organism to change its traits in response to changes in the environment. Such changes do not signal a genetic or evolutionary change.

To rule out phenotypic plasticity, the researchers sought to establish whether the larger, stickier toepads were passed on to the next generation. So the team collected gravid females from invaded islands and non-invaded islands in 2011, raising their offspring in identical conditions. The larger, stickier toepads persisted in the lab-bred offspring conceived on the invaded islands.

“The evidence for an evolutionary change surprised me”, said Stuart. “The pace at which the change was happening surprised me even more.”

The change, all in a matter of 15 years, is even quicker than the change in Mountain Goats that we covered here on SN. But in that study, the authors concluded that the change was not genetic, but rather merely resource driven phenotypic plasticity.