Animal Adaptation: Lizards Adjust For Arid, Limited Environment

Balkan green lizards on Greek islands are not like their (apparently spoiled) mainland relatives. That is, they have adjusted their digestive systems and taste buds to accommodate for the scarcity of food on arid, limited islands. While these lizards generally eat insects, they have evolved to have special valves that help them digest plants, according to a study published recently in The Science of Nature.

According to a news release, Konstantinos Sagonas, of the National and Kapodistrian University of Athens in Greece, led a team of researchers in examining groups of lizards on the islands of Andros and Skyros, along with two other populations from the mainland Greece, that may have had to overcome environmental changes such as less rainfall.

Those researchers found that the island reptiles have a longer small intestine and hindgut compared to the mainland species, and that the lizards from Skyros also had longer stomachs. Surprisingly, cecal valves--which slow food passage and allow it to ferment in chambers--were found in 62 percent of the island lizards and in 19 percent of the mainland species. Combined, these traits slow down the lizard's digestive system by 26 percent, according to their study.  

Cecal valves are generally only found in insect-eating species when they have had to broaden their diets. Sagonas believes this discovery in island lizards reflects the species' increased consumption of plant material, which the researchers found accounts for 30 percent their diet.

"Such adaptations allow insular populations to take advantage of the limited food resources of the islands and, eventually, overcome food dearth," Sagonas explained in the release. "Energy flow in insular environments, the digestive performance of insular populations and the connections within them, provide insights into how animals are able to colonize islands and maintain viable populations."

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