A University of Rhode Island biologist who released lizards on tiny uninhabited islands in the Bahamas has shed light on the interaction between evolutionary processes that are seldom observed, Physorg.com reports.
Jason Kolbe, a URI assistant professor of biological sciences, and colleagues from Duke University, Harvard University and the University of California at Davis, found that the lizards’ genetic and morphological traits were determined by both natural selection and a phenomenon called founder effects, which occur when species colonize new territory.
Their research was published today in the journal Science.
“We rarely observe founder effects as they happen in nature, but we know that it happens because islands are colonized by new species over time,” said Kolbe. “What we didn’t know was how these evolutionary mechanisms interact with each other. What we learned is that the differences caused by the founder effects persist even as populations adapt to their new environments.”
The founder effect is the loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population. It often results in the new population becoming genetically or morphologically different from the original population.
The scientists randomly collected brown anole lizards from a large island near Great Abaco and released one pair on each of seven nearby islands whose lizard populations had been cleared by a recent hurricane. The source island is forested while the other islands have short, scrub vegetation. Previous research found that anoles living in forests had longer hind limbs than those found in scrub habitat. Lizards with longer limbs can run faster on the broad perches available in forests, while short-limbed lizards are more adept at moving on the narrower perches found in lower vegetation.
The scientists revisited each of the islands over the next four years to measure the lizards’ limb length and collect tissue samples for genetic analysis. All of the new populations survived and increased an average of 13-fold in the first two years before leveling off.
“We noticed a founder effect one year after starting the experiment, which resulted in differences among the lizards on the seven islands,” Kolbe said. “Some of the islands had lizards with longer limbs and some had lizards with shorter limbs, but that was random with respect to the vegetation on the new islands.”
For the original report go to http://www.physorg.com/news/2012-02-castaway-lizards-insight-elusive-evolutionary.html
The fetching photo of the anole lizard is from http://www.photosbybruceonline.com/macr_gallery.html