According to new research by Tigga Kingston, a research associate in the Department of Geography at Boston University, and Stephen Rossiter, a National Environment Research Council research fellow in the School of Biological Sciences at Queen Mary, University of London, geographical barriers may not be necessary for speciation. In their study of one species of bat in Southeast Asia, the scientists found that the bats were diverging into exclusive groups primarily because of acoustic differences in the calls they make to locate the insects they eat.
Their finding challenges long-standing theory that geographical barriers are the mechanism by which new species evolve. This new perspective on an old controversy appears in the June 10 issue of Nature.
For centuries, theorists have debated how new species form. Traditional thought holds that speciation occurs over long periods of time as a result of interbreeding among members of a group that are, for one reason or another, isolated from other members of the same population.
If, for example, geologic activity changed an area so that mountains rose and split a region populated by a species of bat, the bat populations on either side of a mountain would no longer be able to breed together. Their genetic information, including changes that lead to physical or behavioral adaptations to the demands of their environments, would no longer be pooled. Future generations of bats found on one side of the mountain would begin to diverge genetically from those on the opposite side. Eventually, the two populations of the bat species would become sufficiently different to qualify as separate species.