Lizards May Help Unlock Secrets of Evolution

Kirsten E. Nicholson, a Central Michigan University assistant biology professor, has just published a paper in PLoS ONE on her four-year study of Caribbean anoles that may provide a building block for future evolutionary studies.

PLoS ONE is a peer-reviewed online scientific journal from the Public Library of Science covering primary research within science and medicine.

In her study of 140 species of anoles on the Caribbean Islands, Nicholson disproved common theories for how anoles evolved by studying each species' distinctive dewlap, a large skin flap beneath the throat.

The highly colorful dewlap has patterns distinctive to each species -- sort of like a flying flag -- and evolutionary biologists study it closely because the anoles fully extend these dewlaps as signals when mating or establishing territory.

Biologists have wondered whether anoles species that live in a very similar habitat, such as a tree top, also developed some of the same dewlap characteristics -- a theory called ecomorph convergence. Other studies have found that anoles in similar micro-habitats have converged in many characteristics. But in her study, Nicholson found no support for the hypothesis: Species in the same micro-habitat were no more similar in their dewlap configuration than expected by chance.

Nicholson also studied whether anole species that co-exist tend to exhibit dewlaps that differ from each other-- a theory called species recognition. Again, Nicholson found very little or no correlation.

One remaining theory to consider is that the dewlaps evolved through sexual selection, Nicholson said. She hopes to examine that in a future study.

Citation: Nicholson KE, Harmon LJ, Losos JB (2007) Evolution of Anolis Lizard Dewlap Diversity. PLoS ONE 2(3): e274. doi:10.1371/journal.pone.0000274 (http://dx.doi.org/10.1371/journal.pone.0000274)