Study Shows Importance Of Competition in Lizard Evolution

Using small Bahamian islands as their laboratory, two U.S. biologists have shown that competition among lizards is more important than predation when it comes to natural selection of the fittest individuals in a population. After covering some islands with netting to keep away predatory birds, leaving other islands open to birds, and adding predatory snakes to others, the Dartmouth College biologists measured survival trends on the different islands. While they found that death by predators occurred at random with respect to traits like body size and running ability, increasing the density of lizard populations consistently increased the competition for food and space, and favored the larger and faster creatures. “The lizard plays for keeps, and there’s no room for the meek when times get tough,” said Ryan Calsbeek, an assistant professor of biology at Dartmouth and co-author of the study, published in the journal Nature. While they cautioned that competition would not necessarily be the most critical factor for other species and in other environments, the researchers said that the results demonstrate that evolutionary experiments can be conducted in natural animal populations.