The bird that came back from the dead

The bird that came back from the dead
White-throated rail. Credit: Charles J Sharp [CC BY-SA 4.0]

New research has shown that the last surviving flightless species of bird, a type of rail, in the Indian Ocean had previously gone extinct but rose from the dead thanks to a rare process called 'iterative evolution'.

The research, from the University of Portsmouth and Natural History Museum, found that on two occasions, separated by tens of thousands of years, a rail species was able to successfully colonise an isolated atoll called Aldabra and subsequently became flightless on both occasions. The last surviving colony of flightless rails is still found on the island today.

This is the first time that iterative evolution (the repeated evolution of similar or parallel structures from the same ancestor but at different times) has been seen in rails and one of the most significant in bird records.

The white-throated rail is a chicken-sized bird, indigenous to Madagascar in the south-western Indian Ocean. They are persistent colonisers of isolated islands, who would have frequent population explosions and migrate in great numbers from Madagascar. Many of those that went north or south drowned in the expanse of ocean and those that went west landed in Africa, where predators ate them. Of those that went east, some landed on the many ocean islands such as Mauritius, Reunion and Aldabra, the last-named is a ring-shaped coral atoll that formed around 400,000 years ago.

With the absence of predators on the atoll, and just like the Dodo of Mauritius, the rails evolved so that they lost the ability to fly. However, Aldabra disappeared when it was completely covered by the sea during a major inundation event around 136,000 years ago, wiping out all fauna and flora including the flightless rail.

The bird that came back from the dead
Wing bones fossils of flighted (right) and flightless Dryolimnas rails. Credit: Dr Julian Hume.

The researchers studied fossil evidence from 100,000 years ago when the sea-levels fell during the subsequent ice age and the atoll was recolonised by flightless rails. The researchers compared the bones of a fossilised rail from before the inundation event with bones from a rail after the inundation event. They found that the wing bone showed an advanced state of flightlessness and the ankle bones showed distinct properties that it was evolving toward flightlessness.

This means that one species from Madagascar gave rise to two different species of flightless rail on Aldabra in the space of a few thousand years.

Lead researcher Dr. Julian Hume, avian paleontologist and Research Associate at the Natural History Museum, said: "These unique fossils provide irrefutable evidence that a member of the rail family colonised the atoll, most likely from Madagascar, and became flightless independently on each occasion. Fossil evidence presented here is unique for rails, and epitomises the ability of these birds to successfully colonise isolated islands and evolve flightlessness on multiple occasions."

Co-author Professor David Martill, from the School of Earth and Environmental Sciences at the University of Portsmouth, said: "We know of no other example in rails, or of birds in general, that demonstrates this phenomenon so evidently. Only on Aldabra, which has the oldest palaeontological record of any oceanic island within the Indian Ocean region, is available that demonstrates the effects of changing sea levels on extinction and recolonisation events.

"Conditions were such on Aldabra, the most important being the absence of terrestrial predators and competing mammals, that a was able to evolve flightlessness independently on each occasion."


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More information: Julian P Hume et al, Repeated evolution of flightlessness in Dryolimnas rails (Aves: Rallidae) after extinction and recolonization on Aldabra, Zoological Journal of the Linnean Society (2019). DOI: 10.1093/zoolinnean/zlz018
Citation: The bird that came back from the dead (2019, May 9) retrieved 26 June 2019 from https://phys.org/news/2019-05-bird-dead.html
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May 09, 2019
This is the kind of real evidence religionists use to justify their fanciful notion of 'kinds' to rationalize how the limited space on the ark could accommodate all the species existing today.

"The biblical concept of created "kind" probably most closely corresponds to the family level in current taxonomy. A good rule of thumb is that if two things can breed together, then they are of the same created kind. It is a bit more complicated, but this is a good quick measure of a "kind."

"Recent studies estimate the total number of living and extinct kinds of land animals and flying creatures to be about 1,500. With our "worst-case" scenario approach to calculating the number of animals on the Ark, this would mean that Noah cared for approximately 7,000 animals."

-See? God would still have had to create the wild divergence we see today in only 6000 yrs, but then stop it before anyone got to actually see it happening.

Which of course still makes no sense. Interesting but sick.

May 09, 2019
Interesting evolutionary flexibility shown by the rails.

Otto, your comment on kinds is interesting, particularly that 7000 figure which brings the ark task down from F*ing impossible to maybe highly unlikely. Records both human and geological show the lack of any flood and the lack of any burst of evolutionary divergence. (Heh, the original rails even had a flood 136,000 years ago and a Noah rail found the island again and repopulated 100,000 years ago.

May 09, 2019
Otto, your comment on kinds is interesting, particularly that 7000 figure which brings the ark task down from F*ing impossible to maybe highly unlikely
Nope still fucking impossible.
Records both human and geological show the lack of any flood and the lack of any burst of evolutionary divergence
Yeah a deer walks into the woods and out walks an antelope. And a viable breeding population ends up in africa.

Poof. Of course nobody ever saw it happen. Like archeologists only dig where solomons kingdom is not.

But then god can do any damn thing he wants to eh? Makes it easy to fill in those gaps, no?

""God of the gaps" is a theological perspective in which gaps in scientific knowledge are taken to be evidence or proof of God's existence. The "gaps" usage was made by Christian theologians not to discredit theism but rather to point out the fallacy of relying on teleological arguments for God's existence."

-poofpoofpoofpoofpoof.

May 09, 2019
and the lack of any burst of evolutionary divergence
Maybe this is called the creationist inflationary era.

POOF.

Gaps not needed.

"15And lo, tho the seed hath emerged from the ark unsullied [because thats the way things were before the Great Flushing] the corruption 16sewed by man did exert itself once more and the seed was scattered 17about the earth, and thus sullied, and caused to shew and mimic what the great satan dawkins would call 18natural selection.

"19And so the hare in the north turned white while the 20jackrabbit in edom was gaunt and stringy. And both were Treif and haram in the eyes of the lord." -Book of Thorns chapV

May 12, 2019
Click bait title, it was not the same species (population) after the repopulation; it most likely was not quite the same fossil species, or even the same genetic trait that down-regulated the wing expression.

your comment on kinds is interesting, particularly that 7000 figure which brings the ark task down from F*ing impossible to maybe highly unlikely.


Every motivated science proposal is more or less likely at the outset. But that sounds like creationism, which is made up belief and simply did not happen.

And yes, the article shows several other reasons why it did not happen.

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