An experiment by University of California, Davis graduate student Daniel Bolnick has captured evolution in action, provided support for a long-standing hypothesis in evolutionary biology, and could help explain how some new species arise from old ones.
Using the fruit fly Drosophila melanogaster, Bolnick has shown that intense competition between members of the same species can drive some individuals into using different habitat niches. Biologists think that this separation into niches marks the beginning of the process of forming a new species.
"It's a long-standing problem in evolutionary ecology," said Bolnick.
"Dan's work represents a current spate of interest in looking for more empirical evidence," said biologist Peter Wainwright, who is Bolnick's thesis supervisor.
The study is published in the March 22 issue of the journal Nature.
When Charles Darwin arrived in the Galapagos Islands, he noticed that there were many more species of finch in the small islands than on the mainland of South America, said Bolnick. Biologists see the same result in other islands and remote places where a single species has arrived and found itself with few competitors.
Animals and plants have to compete for resources both with other species, and with individuals of their own species. These competitive forces balance each other, said Bolnick. In a big environment such as a continent, competition with other species is more important. But when a species -- for example, a finch -- enters an environment such as a remote island with few other species already present, competition within the species becomes more important.
Recent theoretical work shows that intense competition in the "middle" of a population drives more variation at the edges, said evolutionary biologist Sergey Nuzhdin. Bolnick's work provides experimental evidence for this, he said.