Magazine article Science News

Genetics Study Revises Bird Family Tree: Avian Evolution Produced Some Counterintuitive Convergences

Magazine article Science News

Genetics Study Revises Bird Family Tree: Avian Evolution Produced Some Counterintuitive Convergences

Article excerpt

An ambitious genetic analysis of deep avian history strongly supports some counterintuitive ideas about bird evolution that differ from the species groupings familiar in field guides.

Falcons are more closely related to parrots than to hawks and eagles, for instance, researchers report in the Dec. 12 Science. And the new family tree of living birds shows that flamingos' closest relatives are chunky waterbirds called grebes. Both are more closely related to pigeons than to the rest of waterbirds, the new analysis indicates.

Bird history is full of such stories, in which descendants of unsimilar ancestors converge on similar lifestyles, capacities or shapes, says neuroscientist Erich Jarvis of Duke University. He is one of the leaders of the worldwide consortium that produced the new family tree of avian life.

The study relates bird groups in ways that may startle bird-watchers. But whether the new tree shocks scientists "depends on who you are," says Jarvis. "Because there were so many different views out there, so many different trees of birds published, some people said, 'Ah, you confirmed what I said a long time ago,' and others were just torn apart."

Sorting out which modern birds are truly related to each other has been a notorious problem in evolution, says ornithologist Shannon Hackett of the Field Museum in Chicago, who was not involved in the new work. The trouble comes from an avian big bang that sent many lineages flying off in different directions during a relatively short time. Figuring out which fossils belonged with which emerging group has been tricky, as has been sifting reliable signals from the clutter of kinda-similar, kinda-not DNA among living birds. "Some people thought it was unresolvable," Hackett says.

In 2008, Hackett and her colleagues made what was for its time an ambitious push to expand genetic studies by looking at 19 stretches of genetic material for each of 169 bird species. The tree that emerged suggested that many apparent similarities, as between falcons and hawks or grebes and ducks, were convergences instead of close ancestral relationships.

Using new high-capacity genetic technologies, a consortium of about 200 scientists worldwide, with funding from the Chinese genetics institute BGI and other sources, has compiled nearly complete catalogs of DNA's basic units for 48 representative bird species. First the team analyzed DNA containing blueprints for proteins to generate various possible family arrangements. …

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