October 31, 2013
Butterflies Offer Insights Into The Evolution Of New Species
Michael Harper for redOrbit.com - Your Universe Online
A new study from the University of Chicago finds it’s genetically easier to spin off into a new species than it may have once been thought, even if the two species remain close and interbreed with one another. After studying butterflies, the researchers found evolution can happen as the result of a process rather than a single event. In fact, in the case of butterflies, the beginning of a new species could begin with something as simple as a small fraction of a genome resulting in slightly different wing patterns.
“Speciation is one of the most fundamental evolutionary processes, but there are still aspects that we do not fully understand, such as how the genome changes as one species splits into two,” explained Dr. Kronorst.
“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.”
To better understand the origins of evolution, where it really begins, Dr. Kronforst and team studied two different species of butterflies, the Heliconius cydno and H. pachinus. The pachinus has only recently diverged as its own species, providing a good starting point for their research.
Though genetically different on some levels, these two butterflies continue to pass genetic material between one another through breeding. This trading of genetic material was found to turn off specific switches which are unimportant to speciation, giving the researchers a better picture of which genetic markers were affected by natural selection in this evolutionary journey.
The two species only displayed differences in 12 small areas in their genomes. Eight of these areas were responsible for wing coloring, which is important both for protection and population of the species. The other four differences have yet to be determined.
“These 12 spots appear to only function well in the environment their species occupies, and so are prevented from moving between gene pools, even though other parts of the genomes are swapped back and forth,” said Kronforst.
Next, the team went on to investigate a third butterfly species which was further removed from the previous two but still closely related. In this species, Kronforst and his team found hundreds of genomic changes, leading them to conclude that new species can evolve quickly once the initial genetic divergence takes place.
“Our work suggests that a few advantageous mutations are enough to cause a ‘tug-of-war’ between natural selection and gene flow, which can lead to rapidly diverging genomes,” said Dr. Kronforst. “It is possible that this type of speciation, in which natural selection pushes populations apart, has been important in the evolution of other organisms. It remains to be seen whether it is a common process though.”
Kronforst’s research focused on butterflies from the Central American rain forest and plan on further researching why this kind of quick evolution is more common in tropical climates.