The study of butterflies suggested to researchers that evolution may not be as complicated as we thought.
"The butterflies have performed a beautiful natural experiment for us that lets us address important questions about evolution," Marcus Kronforst of the University of Chicago, said in a Cell Press news release. "Even as biologists, we often think of the origin of new species as a moment in time when a new species splits from an old one, and this type of thinking is reflected in the evolutionary 'trees,' or phylogenies, that we draw. In reality, evolution is a long-term process that plays out in stages, and speciation is no different."
The team found new species could evolve even if "diverging" populations remained in contact with the changing species and even continued to breed. The team pinpointed the small section of the butterfly's genome responsible for the beginnings of the divergence. The genes in question were responsible for wing patterns. The researchers looked at species that had important differences in wing patterns.
"We find that only a small fraction of the genome is markedly different between closely related species, but then much more of the genome-more than you'd expect-shows similar differences between more distantly related species," Kronforst said. "That indicates that the genetic changes that are important for causing speciation are tightly clustered early in speciation, but not so later on in the process; the overall pattern of genome divergence starts slow and then skyrockets."
The researchers described the process as a "tug-of-war" between the process of natural selection and the genome. Mutations and gene borrowing have caused a rapid divergence in the species.
"Beyond butterflies, it is possible that this type of speciation, in which natural selection for ecology causes the origin of new species, has been important in the evolution of other organisms," Kronforst said.
