Lizards' FEet Adapt Rapidly Following Ecological Change

From Conservation Magazine

In 1995, a group of researchers led by the University of Tampa’s Todd Campbell turned to a set of man-made islands just off of Florida’s Atlantic coast, on which dwell the United States’ only native Anolis lizard species, Anolis carolinensis, or green anoles. On some of those islands, they released a similar group of lizards, Anolis sagrei, also called brown anoles. Nearly twenty years later, biologist Yoel Stuart returned to those islands as a graduate student in the laboratory of Harvard’s Jonathan Losos (Stuart is now a postdoc at the University of Texas at Austin).

Because the two species use their habitats in similar ways, the researchers expected them to come into conflict. When they’re left alone, green anoles perch on trees anywhere from ground level to the tree’s crown. But in spaces where green and brown anoles were already known to co-exist, the green anoles left the lower parts of the tree to the invaders, retreating to higher ground.

In May 1995, the researchers measured perch height for green anoles on six islands where they were the only lizards, save for the occasional nocturnal gecko. Then they created artificial invasions by releasing brown anoles onto three of them. As expected, the invaders drove the natives up into higher parts of the trees, and that was observable already by August of that year, just three months later. Each summer through 1998 the researchers returned to check up on their lizards, and the vertical divide held up. Green anoles stuck to the higher parts of the tree, and brown anoles perched closer to the ground.

Stuart returned to the islands in 2010. After confirming that the vertical divide had persisted all this time, he turned to the question of evolution. He suspected that the green anoles’ vertical shift would drive the evolution of larger toepads, and with more scales, compared with those from un-invaded islands. “Larger and better-developed toepads improve clinging ability,” he writes, “permitting anoles to better grasp unstable, narrow, and smooth arboreal perches.” And that’s exactly what they found.

In just twenty generations, A. carolinensis had evolved larger toepads with more scales, allowing it to better grasp the smooth tree trunks in the upper reaches of the trees in which it now lived.

See the full article here: http://conservationmagazine.org/2014/10/lizards-feet-adapt-rapidly-following-ecological-changes/