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Flocking genomes! (bird ancestry resolved!)

By Dave Armstrong - 12 Dec 2014 9:45:0 GMT
Flocking genomes! (bird ancestry resolved!)

The fossil Gastornis, at 2m (6.6 feet) looks prettyterrible, but has proved to be a rattite, related to cassowaries and emus and probably vegetarian. The fate of its fellow birds, when it was wading through the dense forests of the Eocene is related superbly by genomic researchers who have put together a tale of natural evolution, red in tooth, and claw and beak ! Gastornis maximus image; Credit: © Shutterstock

We look at so many exotic and plain birds, we should be much more knowledgeable about their convoluted evolution. This magnificent tome of a paper puts together all the flocks of genomes that are so far available and puts the taxonomy in perspective. Passerine birds are the songbirds and others we know well, whereas columbines or doves group together as a separate set. All is revealed in the journal Science today. Erich D Jarvis of the US Duke University, NC, is the lead author, but hundreds of researchers from many nations have been involved in this deepest of international studies of 48 genomes by the Avian Phylogenomics Consortium.

The rapid radiation of the bird type during the age of dinosaurs becomes evident from this extensive research paper. The ambition to produce proof of the connection between the demise of the dinosaur and the soaring of bird diversity has been vindicated. Either two or three independent origins for vocal learning are suggested, with two later losses, including the New Zealand wrens. The common ancestor of all land-birds appears to be a top predator. This reminds us of those awesome terror birds that have fossils from the Paleogene and their living raptor relatives, still possessing a little shock and awe.

The gradual loss of the raptor type of foot took place among two groups of core land-birds. There is evidence that the doves and passerine birds have converged to act alike. Foot-propelled diving in grebes (dove relatives) resembles the cormorant or loon dive in the passerines. The flamingos (dove relatives) resemble the passerine ibis and egret for similar locomotive reasons. They have converged with the wading habit.

The end result is the confirmation of quick radiation of early species within 10-15 million years. This took place from the late Palaeocene to the Eocene, just as the mammals were radiating. 36 lineages are confirmed using these molecular clock techniques plus a range of new methodologies, but many smaller divergences of species are also visible. Modern speciations are equally spectacular, again with many lines surviving, compared to other animals. The famed asteroid extinction could well be another reason for the rapid radiation of species into ecological niches that were previously occupied.

100 million years ago, birds made an appearance, but it was only during their window of opportunity that they radiated rapidly into modern types. This was the 10-15 million years that followed the loss of the dinosaurs. Then the eagle, owl and falcon ancestor terrorised the planet before it apparently quietened down in the form of new speciations that became our current vast set of passerine and columbine species. Many more birds and genomes are here, including bouncing birds and the association of flying with genome size!