News Excerpt:

By analysing the genomes of 363 bird species, a new study has identified the fundamental relationships among the major groups of living birds.

More about the study:

• The study published in the journal “Nature”, shows that most of the modern groups of birds first appeared within 5 million years after the extinction of the dinosaurs.
• The genome study is the product of nearly a decade of research, conducted as part of the Bird 10,000 Genomes Project. 

Bird Family Tree:

• Previous studies showed the bird family tree has three major branches: 
• The first branch contains the tinamous and ratites.
• They include flightless birds such as the emu, kiwi and ostrich.
• The second branch holds the landfowl and waterfowl.
• Examples are chickens, ducks etc.
• All other birds sit on the third branch, known as the Neoaves, which includes 95% of bird species.
• This branch includes ten groups of birds. 
• Biologists have named most of these as “Magnificent Seven”: landbirds, waterbirds, tropicbirds, cuckoos, nightjars, doves and flamingos. 
• The other three groups are known as the “orphans” and include the shorebirds, cranes and hoatzin.
• The relationships among these ten groups, especially the orphans, have been incredibly difficult to resolve. 
• The genome study shows a resolution is within reach.
• The new family tree overturns some previous ideas about bird relationships, while also revealing some new groupings.

Elementaves:

• The genome study has revealed a new grouping of birds named “Elementaves”.
• The name is inspired by the four ancient elements, “earth, air, water and fire”.
• This group includes birds well adapted for success on land, in the sky and in the water. 
• Some birds have names relating to the sun, representing the element of fire.
• E.g.-  hummingbirds, shorebirds, cranes, penguins and pelicans.

More findings of the study:

• The study also confirms a close relationship between two of the most familiar groups of birds in Australia, the passerines (songbirds and relatives) and parrots. 
• These popular birds have dominated the Australian Bird of the Year polls.
• Songbirds make up nearly 50% of all bird species and include birds like magpies, finches, honeyeaters and fairywrens. 
• They had their humble beginnings in Australia about 50 million years ago, then spread across the globe to become the most successful group of birds.
• The study could not confidently determine the relationships of one of the orphan birds, the hoatzin. 
• Found in South America, the hoatzin is a highly distinctive bird and the sole survivor of its lineage.

Timescale on the Bird Family Tree:

• A further goal of our study was to place a timescale on the bird family tree. 
• It was done by modelling the evolution of genomes using a tool known as the “molecular clock”. 
• By drawing on information from nearly 200 fossils, it was possible to constrain the ages of some of the branches in the bird family tree.
• The study shows all living birds share an ancestor that lived just over 90 million years ago. 
• But most groups of modern birds emerged about 25 million years later, within a small window of just a few million years after the end of the Cretaceous period around 66 million years ago.
• This coincides with the mass extinction of dinosaurs and other organisms caused by an asteroid striking Earth. 
• So it seems birds made the most of the opportunities that became available after these other dominant life forms were wiped out.

Molecular Clock:

• The molecular clock is a method that uses biomolecular data (generally mutation rates) to estimate the amount of time needed for a certain amount of evolutionary change to occur. 
• The molecular clock hypothesis argues that DNA and protein sequences mutate at a constant rate over time among different organisms and that the number of genetic differences between organisms can give us an estimation of when they last shared a common ancestor. 

Conclusion:

The genome study is the product of nearly a decade of research, conducted as part of the Bird 10,000 Genomes Project. The ultimate goal of this project is to sequence the genomes of all 10,000 living bird species. The research shows that some relationships in the tree of life can only be determined using huge amounts of genome data. It also demonstrates the power of studying genomes and fossils together to understand the evolutionary history of life on Earth.