LIZARDS' CAMOUFLAGE REVEALS EVOLUTION IN ACTION

In White Sands, N.M., two species of traditionally brown lizards have evolved white scales in order to blend in with their environment.

By studying the genetic mechanisms at work in this adaptation, scientists are able to observe evolution as it happens. The study illuminates the mechanics of not only adaptation, but also speciation, or how species form.

Erica Bree Rosenblum of the University of Idaho led the study, published in the Proceedings of the National Academy of Sciences, in which her team analyzed the gene responsible for producing the skin pigment melanin.

"(In this study), we have an opportunity to showcase 'evolution in action,'" Rosenblum told Discovery News. "The evolution at White Sands has occurred remarkably quickly and with dramatic results."

In two of the species studied by Rosenblum and her team, the fence lizard and the whiptail lizard, the researchers found that pigment-producing genes in each species had mutated. However, each lizard evolved this mutation differently on a molecular level.

In other words, when presented with the challenges of desert life in White Sands, each lizard species arrived at the same solution in a slightly different way. Rosenblum estimates that the white fence and whiptail lizards adapted to their pallid surroundings between 2,000 and 5,000 years ago, a blink of the eye in evolutionary terms.

What's more, they're in the process of evolving into two separate species from their brown counterparts -- a fact the researchers find particularly exciting.

While scientists often disagree about what constitutes a new species, Rosenblum added that several of the "road stops" on the path to speciation have been met. For instance, some of the animals already exhibit mating preferences for like-colored lizards.

According to Dr. Kevin J. McGraw, the study stands as one of the more impressive evolution in action events observed by scientists. McGraw, an associate professor at Arizona State University, explores pigment changes in birds.

As with Rosenblum's lizards, his work provides insight into the evolved diversity of exaggerated features in the animal kingdom.

"Because body pigments can play such diverse physiological and morphological roles, pigment-based color patterns represent ideal systems in which to evaluate fine-scale evolutionary pressures, changes and trade-offs