Are ostriches, emus, kiwis, really related?


From LiveScience:

Theory of Flightless Birds Shot Down

By Robin Lloyd, LiveScience Senior Writer

posted: 08 September 2008 09:40 am ET

Ostriches, emus, kiwis and other winged non-flyers might seem to be birds of a feather, sharing similar evolutionary origins, but the story could turn out to be much weirder with perhaps numerous flying ancestors.

This group of birds, called ratites, has been viewed by biologists as part of a larger group (paleognaths) of mostly extinct birds that are key to understanding the early evolution of birds. All living ratites are found in the Southern Hemisphere and share features associated with flightlessness, such as small or absent keels on their breastbones; smaller, simpler and fewer wing bones; bigger leg bones; and structures in their feathers that don’t help with aerodynamics.

So for these reasons and others, many scientists previously figured the ratites, a group that also includes rheas and cassowaries [see also here and here and here], all shared a common ancestor that was flightless.

However, a new analysis shows they do not share this single hypothetical flightless ancestor. Rather they probably evolved from more than one different airborne ancestor.

Ostriches are special

The research, led by John Harshman of the Field Museum of Natural History in Chicago, Edward L. Braun of the University of Florida and Michael J. Braun of the Smithsonian’s National Museum of Natural History, was based on sequencing genetic material sampled from the tissues of many different bird species and using the gene sequences to determine how the birds relate to one another.

Nearly all of the ratites, except for ostriches, which the analysis revealed as a class unto themselves, are actually more closely related to tinamous (a chubby, ground-dwelling bird with a stubby tail, that nonetheless can fly and lives in Central and South American) than they are to ostriches, says UF zoologist Edward L. Braun. The analysis also placed tinamous in a sub-group that includes rheas, cassowaries, emus and kiwis but excludes ostriches.

“We think the most likely hypothesis is that the tinamous, rheas, cassowaries, emus, and kiwis had an ancestor that could fly, and that flight was lost at least three times (once in ostriches, once in rheas, and once in the emu-cassowary-kiwi group),” Braun said.

Julia Clarke, a paleontologist at North Carolina State University, said the results are surprising, the analyses are well done and the dataset used for them is the largest one available. “It is unquestionable that any future analysis will need to address this dataset,” she said, “but the results are in conflict with nearly every previous hypothesis of relationships within paleognath birds.”

New idea takes flight

The result also undermines continental drift as the explanation for how flightless birds became so far-flung — ostriches today live in Africa; rheas in South American; emus and cassowaries in Australia and New Guinea; kiwis and moas (the latter now extinct) in New Zealand; and elephant birds (also now extinct) in Madagascar. Some zoologists had thought the birds’ distribution reflected the order in which the continents broke away from the early super-continent of Gondwana.

But it looks like there is a much simpler explanation for the distribution of ratites’ ancestors, once Gondwana started to break up 167 million years ago. They flew.

“Our idea provides another explanation for the distribution of ratites — it becomes reasonable to postulate that they flew to their new homes and only lost flight after dispersing,” Braun told LiveScience.

Clarke said that if the new results are confirmed with a new set of genes or other combinations of data,” there could be profound implications for our understanding of major trends in bird evolution, such as patterns and potential explanations of flightlessness.”

The finding is also exciting from a developmental standpoint, he said, given how similar most ratites look. The ratites apparently all arrived at similar body shapes through different evolutionary routes, a concept called convergence (for example, birds, bats, insects and pterosaurs all have or had wings, but they are not all closely related).

“This raises an interesting question — what genetic mechanisms lead to these similarities, and can we identify them by looking at how ratite chicks grow in the egg,” Braun said.

The research, funded by the National Science Foundation, is detailed this week in the online edition of the journal Proceedings of the National Academy of Sciences.

Ratite and dinosaur evolution: here.

Moa research in New Zealand: here. And here.

A new Transantarctic relationship: morphological evidence for a Rheidae–Dromaiidae–Casuariidae clade (Aves, Palaeognathae, Ratitae): here.

DNA recovered from fossilized bones of the moa, a giant extinct bird, has revealed a new geological history of New Zealand, reports a study published this week in the Proceedings of the National Academy of Sciences: here.

Moa fed on nectar-rich flowers from flax and tree fuchsia, according to scientists analysing fossilised moa dung near Karamea: here.

12 thoughts on “Are ostriches, emus, kiwis, really related?

  1. Secrets of ancient extinct bird revealed

    Researchers have performed the first DNA-based reconstruction of the extinct giant moa bird.

    Using prehistoric feathers and retrieving DNA believed to be 2,500 years old, the researchers have identified four different moa species.

    Adelaide University student, Nicolas Rawlence, says until now the scientific community had not known what the 10 different species of the New Zealand bird looked like.

    “It’s one of those enigmatic birds like the dodo and the great auk, one of those symbols of extinction that will get people quite interested,” he said.

    “It’s quite amazing to see the reconstruction completed because with it we can start comparing it to other bird species in New Zealand.”

    “It’s the type of moa that has been previously described from fossil bones but it is the first time anyone has accurately reconstructed what the plumage or what colour the moa was, so it is opening up a whole new window to accurately study the ecology of this extinct group of birds.”

    http://www.abc.net.au/news/stories/2009/07/01/2613299.htm

    More about this: here.

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  5. Kenya: Nairobi Park Diary – Mbuni Tales

    By Gareth Jones, 29 December 2012

    Just a few weeks ago many people observed many Ostrich couples pairing during their mating season with elaborate wing flapping dances and very red necks the males do everything possible to attract the female to ensure they continue to survive.

    I always enjoy this time of year in the park when the chicks hatch as it is quite a sight to see more than 20 small fluffballs following their parents.

    Unfortunately the chick mortality is high due to predation. However, a healthy population of about 150 ostrich live in the Nairobi park.

    They are interesting to watch. They are the largest birds in the World and cannot fly due to size and weight. However, to compensate for the inability to fly, ostrich can run quite fast and if threatened will turn sharply and twist at full speed.

    The males look majestic with their black feathers and white undercarriage while the females are a drab grey. Just imagine if women in our world looked drab and did not care for fashion?

    They also regularly swallow stones to help the digestion process. It is no wonder they can’t fly with that extra weight! The species in the Nairobi park are the southern sub-species with pink/reddish legs.

    Kenya is also one of the few places where the rarer northern (Somali ostrich) sub-species with its blue legs is found. Locally Ostrich are also known in Kiswahili as Mbuni.

    So bring the family and spend the day in the park, go with a “birdwatching” attitude and you will be surprised at how many other animals can also be seen, if you slow down to the pace of nature.The park is open daily from 06h00 to 19h00.

    For more information on the park you can link to the following websites http://www.kws.org or http://www.nairobigreenline.com or on facebook.

    http://allafrica.com/stories/201212310432.html

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