A phylogenetic tree illustrating evolutionary relationships and beak variation among 350 lineages of ovenbirds. Credit: Joseph A. Tobias and D. Seddon, images reproduced with the permission of Lynx Edicions.
By focusing on ovenbirds, one of the most diverse bird families in the world, a team conducted the most in-depth analysis yet of the processes causing species differences to evolve. They found that although bird species occurring together were consistently more different than species living apart, this was simply an artifact of species being old by the time they meet. In fact, once variation in the age of species was accounted for, coexisting species were actually more similar than species evolving separately.
"The reason seems to be linked to the way new species originate in animals, which almost always requires a period of geographic separation. By using genetic techniques to establish the age of lineages, we found that most ovenbird species only meet their closest relatives several million years after they separated from a common ancestor. This gives them plenty of time to develop differences by evolving separately," says Dr. Joe Tobias of Oxford University's Department of Zoology, who led the study.
