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An island half the size of Manhattan, in the South Atlantic Ocean, is so isolated that it is nicknamed Inaccessible Island. On this island, and only on this island, live nearly 6,000 puny feathers called Inaccessible island rails. But they can not fly and the island is only a few million years old. How did the birds get there?
A new analysis may have solved the mystery. The bird's DNA reveals that it has evolved relatively recently from a visitor to the island and has lost its ability to fly through the forces of natural selection.
"It's quite dramatic that the world's smallest live birds have found themselves in one of the most remote places of all time," Martin Stervander, postdoctoral researcher, told Gizmodo, the study's author. from the University of Oregon. "It seems that the birds arrived on the island, and since they were not threatened by predators, there was no real reason to fly."
When scientists first described this bird in the 1920s, they immediately realized that they were seeing something odd. Inaccessible Island lies 3,500 kilometers from South America and 2,800 kilometers from southern Africa. The bird occupies neither of the two neighboring islands within 20 km. Before the theory of plate tectonics, they proposed that the bird would move one way or another to the island by some kind of land bridge below. They placed him in his own kind, Atlantisia. More recent research has suggested that the bird came from rails in Africa.
The scientists behind the new document have analytical tools other than the shape and geography of birds. They captured an inaccessible male insular rail in September 2011, took its blood, sequenced its DNA and compared the results to data from other rails. They deduced that the rail ancestor was a South American bird that arrived on the island about 1.5 million years ago and was more likely to be a member of the Laterallus The genus, which includes today's birds such as black-winged gypsum, Galapagos gypsum and the same-looking black rattle, according to the article published in the journal Molecular Phylogenetics and Evolution.
It makes sense. It is known that rails fly everywhere and settle, with 53 existing or recently extinct species appearing only on islands and 32 species losing all or part of their flight capacity. An ancestor population of Inaccessible Island Rail probably came from the east in the Atlantic to land on the island, which was nice enough that they no longer needed to fly.
"When the rail arrived at Inaccessible Island, they only had food to move around and there was no need to escape, there was no big-to-flying," said Stervander . The only threats to the bird on Inaccessible Island are another species of bird that sometimes eats eggs and perhaps some seabirds.
We do not know why the rail did not go to the other two islands. Perhaps a population has tried and failed.
Stervander pointed out that there was still a lot of research to be done. The dataset on the rails was incomplete, so maybe more data will reveal that the bird really belongs to a distinct kind.
And although the bird lives well, it is still considered a vulnerable species. Bird populations that are unable to fly can easily collapse if humans bring invasive species, such as cats or rats, with them.
This document solves perhaps the cutest mystery of the South Atlantic Ocean. But if you plan to visit the island (which is not easy), be sure to do nothing that can hurt the birds.
[Molecular Phylogenetics and Evolution]Source link
