Iguana's “Rafted” 8,000 kilometers from North America to Fiji – a record for country vertebrate

Even if you can swim, country residents cannot make it over the oceans under their own steam. Nevertheless, sometimes clearly related animals appear large distances without a plausible way to avoid. The most famous example of this is the way monkeys suddenly appear in the South American fossil record 36 million years ago. Apparently it was on a vegetation at sea and managed to over the Atlantic without dying from thirst. To round off the whole thing, the family tree of the New World Monkey suggests that another bunch of millions of years later did.

Leguane are a very successful family through a large part of America with 45 surviving species. However, they are not known from other continents. But somehow there are four living species in Fiji and Tonga, together with an extinct. The obvious answer is that they came across Asia and maybe had arrived there at a time when the continents were closer together. Alternatively, Iguane could have used it as a bridge to Australia and then in the western Pacific before the Antarctic was covered with ice. However, there is no fossil evidence of one of these explanations.

When Simon Scarpetta from the University of San Francisco and co-authors examined the genetics of the Iguan family tree and the Fijian genre BrachylophusThese stories became even less plausible in it.

“We found that the Fiji Leguane were most closely related to the North American desert lens, which had not yet been found, and that the descent from Fiji -Iguanas was recently separated from her sister line 30 million years ago to 30 million years,” said Scarpetta in a statement.

This timing is not much younger than the age of the volcanic islands from which Fiji consists.

Instead, scarpetta and co-authors argue, Brachylophus Cross the Pacific Ocean on rafts that were washed out in storms at sea. We saw how you did shorter trips between the Caribbean islands, and we are confident that you have come to the Galapagos in this way, but that is all quite locally compared to sailing the largest width of the world's largest ocean. This even leaves the impression to hit a small island at the end of her trip.

“That they reached Fiji directly from North America,” said the University of California, Berkeley Professor Jimmy McGuire. However, if you have excluded the impossible, the unlikely must be accepted. “Alternative models that contain colonization from adjacent land areas do not really work for the period, since we know that they have arrived in Fiji over the past 34 million years,” McGuire continued.

If it were not for this type of ocean transitions, volcanic islands would be largely sterile, apart from what birds and bats bring.

The sheer length of this trip, both in time and in the distance, shows it. Trapdoor spiders have crossed the Indian ocean from Africa to Australia, but a large part of the trip was probably supported by the roaring 40s. The iguanas had to make it through the doldrums, although there are some evidence that the currents were cheaper 34 million years ago. The capacity of desert species of walking without water for a long time would have been useful, but the authors find that at that time it probably lived in the habitats of North America.

“My thinking process is if there had to be a group of vertebrate or a group of lizards that could really make an 8,000 kilometer journey through the Pacific on a mass of vegetation, an Iguan ancestor of the deserts would be the one,” said Scarpetta.

“You can imagine that a kind of cyclone knocked on trees where there were a few Iguanas and maybe their eggs, and then they catch the sea currents and rafted over,” said Scarpetta.

The study is published in Proceedings of the National Academy of Sciences.