Adelaide/Sydney, The most extensive investigation of bird genomes to date has provided a remarkably clear depiction of the bird family tree. The findings, published in the journal Nature today, reveal that the majority of modern bird groups originated within 5 million years following the extinction of the dinosaurs.
Birds play a significant role in our daily lives, symbolizing nature even in urban environments. They are beloved by the general public and extensively researched by scientists. However, organizing these birds into a cohesive family tree has been a challenging task.
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By scrutinizing the genomes of over 360 bird species, our research has elucidated the essential relationships among the primary bird groups.
The newly unveiled family tree challenges previous notions about bird relationships and unveils novel groupings.
Untangling a Complex Web of Relationships
Earlier studies depicted the bird family tree as comprising three primary branches. The first branch encompasses tinamous and ratites, which consist of flightless birds like the emu, kiwi, and ostrich.
The second branch encompasses landfowl and waterfowl – encompassing chickens, ducks, and similar species. The remaining birds are situated on the third branch, known as Neoaves, which encompasses 95% of bird species.
The Neoaves branch includes ten bird groups, with the majority falling under the category of the “Magnificent Seven” – landbirds, waterbirds, tropicbirds, cuckoos, nightjars, doves, and flamingos. The remaining three groups, termed the “orphans”, include shorebirds, cranes, and the hoatzin, a unique species native to South America.
Deciphering the relationships among these ten groups, particularly the orphans, has been a formidable challenge. However, our genome analysis suggests that a resolution is now within reach.
Introducing the ‘Elementaves’
Our genomic investigation has unveiled a novel grouping of birds known as “Elementaves”. Inspired by the ancient elements of earth, air, water, and fire, this group comprises birds well-adapted for terrestrial, aerial, and aquatic environments. Some birds within this group are named after the sun, symbolizing the element of fire. The Elementaves category includes hummingbirds, shorebirds, cranes, penguins, and pelicans.
Furthermore, our study confirms a close relationship between two iconic bird groups in Australia – the passerines and parrots. These popular birds consistently dominate the Australian Bird of the Year polls.
Songbirds, constituting nearly half of all bird species, include familiar birds like magpies, finches, honeyeaters, and fairywrens. Originating in Australia approximately 50 million years ago, they later dispersed worldwide to become one of the most successful bird groups.
Unveiling the Origins of Birds
Another objective of our study was to establish a timeline for the bird family tree. Utilizing a tool known as the “molecular clock” to model genome evolution and drawing insights from nearly 200 fossils, we managed to estimate the ages of various branches in the bird family tree.
Our research indicates that all extant birds share a common ancestor that lived just over 90 million years ago. However, the majority of modern bird groups emerged approximately 25 million years later, within a narrow timeframe shortly after the conclusion of the Cretaceous period around 66 million years ago.
This period coincided with the mass extinction of dinosaurs and other species triggered by an asteroid impact on Earth. Birds evidently capitalized on the ecological niches left vacant by the disappearance of these dominant life forms.
A Lingering Enigma
The genome study represents the culmination of nearly a decade of research conducted as part of the Bird 10,000 Genomes Project, which aims to sequence the genomes of all 10,000 extant bird species.
The recent phase of the project focused on including species from every major bird group or family. This extensive study involving 363 genomes was an international collaboration led by researchers from the University of Copenhagen, University of California San Diego, and Zhejiang University in China.
Despite the wealth of genome data analyzed, one branch of the bird family tree remains enigmatic. Our analysis was unable to definitively determine the relationships of one of the orphans, the hoatzin. This distinctive bird, native to South America, stands as the sole survivor of its lineage.
Our study underscores the necessity of vast genome datasets in resolving certain branches of the tree of life. It also highlights the power of combining genomic analysis with fossil evidence to unravel the evolutionary history of life on Earth.