- Title: DENMARK-BIRD BIG BANG Mass bird genome study reveals close links with dinosaurs
- Date: 11th December 2014
- Summary: LONDON, ENGLAND, UNITED KINGDOM (RECENT) (REUTERS) STEGOSAURUS FOSSIL SKULL
- Embargoed: 26th December 2014 12:00
- Topics: General
- Reuters ID: LVA19LHLH6EHC08JNJGUOTRN1G2P
- Story Text: An unprecedented large-scale international collaboration has sequenced the genomes of 45 avian species, allowing scientists to create arguably the most reliable avian tree of life yet put together.
The Avian Phylogenome Project reveals how some of the earliest bird species diverged and reveals a host of information on the common ancestor of birds, crocodilians, and dinosaurs - a group collectively known as archosaurs.
The creation of the avian family tree seeks to clarify how modern birds emerged rapidly from a mass extinction event that wiped out the dinosaurs more than 65 million years ago.
According to one of the lead authors, Professor Thomas Gilbert, from the Natural History Museum of Denmark, the genomic sequencing of so many bird species will help us gain a far better understanding of the lives of the dinosaurs.
"Birds are the living dinosaurs," Gilbert told Reuters. "Dinosaurs didn't go extinct, birds are the living relatives of them. Now what we've done is we've sequenced genomes, we've generated a dataset of 48 bird genomes and they span the complete diversity of modern birds, and we did this for several reasons. Firstly, once we've got this genomic dataset we can look at a number of questions relating to birds. But secondly we can start to infer things about dinosaurs."
The analysis dates the evolutionary expansion of Neoaves - the grouping of all modern birds - to the time of the mass extinction event that killed off all dinosaurs except some birds, which contradicts other studies suggesting that they thrived up to 80 million years earlier. The data suggests only a few bird lineages survived the mass extinction, giving rise to the 10,000 or so Neoaves species that comprise 95 percent of all modern bird species. Gilbert says the extinction event probably allowed rapid species radiation of birds in less than 15 million years.
"By finding that the birds probably did go bang and explode about 65 million years ago it suggests they never did it before because the dinosaurs were there, so the dinosaurs were effectively filling all the kind of different habitats you can fill and the birds didn't have a sort of chance to replace anything, " said Gilbert. "So firstly it tells us that dinosaurs were very, very successful, but actually what it then starts to tell us is we can look at what genetic features are basically common to all birds and by this you can then infer that they were probably present in dinosaurs and we can find a number of things. For example, all birds have got pretty small genomes and this again might tie in to the ability to fly."
Speaking last year to Reuters, Professor John Hutchinson, of the Royal Veterinary College's Structure & Motion Lab, who was not part of the study, pointed out how closely related the emu was to the dinosaurs. "If we look at an emu we can see a lot of similarities with extinct dinosaurs. That's because they are dinosaurs, they still have features that the earliest dinosaurs had, like a three-toed foot, long muscular legs, they even have little tiny claws on their forelimbs, their wing stubs," he said.
The researchers produced a total of 28 studies - eight of which are being published simultaneously in the December 12 issue of leading journal Science. A further 15 are being published in Genome Biology, GigaScience and other journals.
The project, which required several supercomputers to process all its data, took more than four years to complete. Hundreds of scientists from approximately 80 institutions in 20 different countries were involved.
In one project led by Guojie Zhang and Cai Li, of the Beijing Genomics Institute (BGI), 45 new avian genome sequences, such as crow, duck, pigeon, falcon, woodpecker, eagle, and ostrich, were compared with those of chicken, turkey, and zebra finch, which were already available.
A team at Duke University described how vocal learning may have evolved independently in a few bird groups and in the human brain's speech regions. They posit that 10 percent of a bird's genome is regulated by singing.
"They sequenced the genome of the budgerigar, one of these sort of small parrots that you can buy everywhere, and by actually analyzing both the brain structure and genomic information they can look for sort of what genes are important in this vocal line, this kind of advanced vocalization behavior and therefore expand from this and try to understand how humans talk," said Gilbert.
One report by Robert Meredith, from Montclair State University, helps explain the process that led to birds losing their teeth. Meredith suggests that the mutations that eliminated enamel and dentin from the teeth of modern birds began about 116 million years ago.
In other research it is revealed that the sex chromosomes of various bird species are currently at different stages of evolution, while saltwater crocodiles and American alligators' genomes are evolving exceptionally slowly.
Most attention, however, will probably rest on the announcement of the new avian tree. The findings support three independent origins of waterbirds, while indicating that the common ancestor of core landbirds, which include songbirds, parrots, woodpeckers, owls, eagles and falcons, was an apex predator, which also gave rise to the giant terror birds that once roamed the Americas.
Until this large-scale collaborative project, scientists would use a handful of a bird's genes to try to infer bird species relationships. Gilbert and co believe that taking the whole genome gives a far more accurate species tree.
"We haven't done this, but what in theory can be done is we can look at the kind of genetic variability across all birds and look for what is shared between them and come up with the kind of theoretical genome of the dinosaur," said Gilbert. "That hasn't been finished yet but once that's been done we can actually start to make predictions about features that dinosaurs had, so going from beyond the information from a single little bone, we can actually suggest that dinosaurs had this kind of metabolism or they had these kind of feathers, for example, or they had this kind of vision or this kind of smell or even this kind of brain."
Frozen bird tissue samples collected over the past 30 years by museums and other scientific institutions were used as the basis for the genome sequencing that was undertaken primarily at the BGI.
The consortium is now creating a database to be made publicly available for scientists to study.
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