Corl found the three color morphs in many places, but not everywhere. Some populations were missing some of the color morphs. For example, populations in the northwest only have orange-throated lizards, while only orange- and blue-throated morphs are found on Anacapa Island in the Channel Islands. In the field, the researchers captured lizards to collect tissue samples for DNA analysis and then released them back into the wild. In the lab, they used the tissue samples to get DNA sequences from all of the lizard populations in the study.
"Based on these sequences, we reconstructed the 'family tree' of the lizard populations and figured out which populations were more closely related to one another. This let us figure out how the mating strategies evolved," Corl said.
The results showed that all three color morphs existed millions of years ago and have persisted since then in many populations. Over time, however, some branches of the lizard family tree lost some of the color types.
"What was particularly interesting was the pattern in how color morphs were lost," Corl said. "Any time there was a loss, the yellow type--the sneaky males that mimic females--was the first to go. Thus, the rock-paper-scissors game can break down on an evolutionary timescale. Something about the game must change so that, for instance, both the rock and scissors strategies are able to beat paper."
Sinervo has documented the cycling of the rock-paper-scissors game at his main study site for 22 years, with the dominant morph in the population changing every four to five years. "It's like an evolutionary clock ticking between rock, paper, scissors then back to rock," he said. "Ammon's research indicates that the game has been cycling for millions of year
|Contact: Tim Stephens|
University of California - Santa Cruz