A new family tree of the world's bird species may be the most complete one ever made, and reveals some surprising relationships, as well as showing how characteristics such as birdsong evolved.
More than 200 scientists at 80 institutions spent more than four years sequencing the genomes of bird species and analyzing them using supercomputers as part of a massive effort to reconstruct how birds evolved.
The new bird genealogy is the most comprehensive one to date in terms of the amount of genomic data and the scientific approaches used, said Erich Jarvis, a neurobiologist at Duke University in Durham, North Carolina, who led one of eight reports based on the findings published today (Dec. 11) in the journal Science. [Animal Code: Our Favorite Genomes]
In one finding, the analysis revealed that the common ancestor of a group called the core landbirds — which includes today's songbirds, parrots and woodpeckers — was a top-level predator of its time, the researchers said.
Previous studies have tried to reconstruct the relationships between bird species using just a few dozen genes, but each study gave different results. "You couldn't figure out who to believe," Jarvis said.
More than 10,000 bird species are alive today, and from the colorful birds-of-paradise of New Guinea, to the iconic blue-footed boobies of the west coast of the Americas, birds are some of the most varied and fascinating creatures around.
Bird family secrets
In the new project, the researchers analyzed the genomes of 48 bird species (including 45 that had not been sequenced before), representing all major branches of birds, including the crow, duck, falcon, parakeet, crane, ibis, woodpecker and eagle. About 95 percent of today's birds belong to a group called Neoaves, and most of the species the researchers analyzed belong to this group.
The new findings show that Neoaves underwent a "Big Bang" of evolution, with many new species appearing within just a few million years of the time that most dinosaurs went extinct about 66 million years ago. Previous work had suggested a more gradual evolutionof this group.
Neoavesinitially split into two groups, called Columbea and Passerea, Jarvis and his colleagues said.
One of the most surprising findings was that flamingoes are closely related to pigeons, much more so than they are to birds that might seem more similar, such as pelicans, the researchers said.
Another important finding was that vocal learning, which is the ability to hear sounds and reproduce them (a key feature of human speech), may have evolved independently in several groups of birds. What's more, a brain region in these birds shares similarities with human brain areas involved in speech.
Constructing the tree
To construct the family tree, the researchers used supercomputers to compare the complete genome sequences of all the birds studied. Using nine supercomputers, the analysis took 300 CPU years (a CPU year is the time it would take a single computer to complete the task on its own).
Birds have smaller genomes than most other vertebrates, but even with these powerful tools, some parts of the tree were hard to flesh out. It wasn't enough to look at the parts of the genome that encode proteins, the vital biological machinery in cells, the researchers found. They had to look at non-coding sequences between genes, too.
Other findings based on the new research offer clues to how birds' sex chromosomes evolved, how birds came to lose their teeth, how birdsong regulates genes in the brain, as well as details about the common ancestor of birds and crocodiles.
In addition to the studies in Science, an additional 21 reports based on the work are published in other journals.