GAINESVILLE, Fla. --- Large flightless birds of the southern continents African ostriches, Australian emus and cassowaries, South American rheas and the New Zealand kiwi do not share a common flightless ancestor as once believed.
Instead, each species individually lost its flight after diverging from ancestors that did have the ability to fly, according to new research conducted in part by University of Florida zoology professor Edward Braun.
The new research, which appears this week in the online edition of the Proceedings of the National Academy of Sciences, has several important implications.
First, it means some ratites, like the emus, are much more closely related to their airborne cousins, the tinamous, than they are to other ratites, Braun said.
Second, it means the ratites are products of parallel evolution different species in significantly different environments following the exact same evolutionary course.
Braun and his fellow researchers began closely studying this group of flightless birds, known collectively as ratites, after a discovery made while working on a larger-scale effort to better understand the evolution of birds and their genomes by analyzing corresponding genetic material sampled from the tissue of many different bird species and determining how they relate to one another.
As they analyzed the genetic material, they noticed that the ratites did not form a natural group based on their genetic makeup. Rather, they belonged to multiple related but distinct groups that contained another group of birds, the tinamous, with the ability to fly.
Previously, the ratites were used as a textbook example of vicariance, a term that describes the geographical division of a single species, resulting in two or more very similar sub-groups that can then undergo further evolutionary change and eventually become very distinct from one another.
Scientists assumed that a
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University of Florida