NEW YORK – The mystery of how iguanas reached Fiji, a group of isolated islands in the South Pacific, has puzzled researchers for a long time. Most of today’s iguanas are found in the Americas, separated by thousands of miles and an entire ocean.
They thought maybe they scurried there through Asia or Australia before volcanic activity pushed Fiji so far away.
Recent studies propose that millions of years ago, iguanas managed to make a 5,000-mile (8,000-kilometer) journey by floating on masses of uprooted trees and vegetation across the ocean. This trek is believed to be an extraordinary feat, surpassing the travel distances of any other terrestrial vertebrate over water.
Researchers initially speculated that iguanas traveled to locations such as the Galapagos Islands near Ecuador and among Caribbean islands using this method. Initially, they were unsure if Fiji was within the feasible range for such a voyage. However, a recent study analyzed the genetic makeup of 14 iguana species from regions spanning the Americas, the Caribbean, and Fiji. The findings revealed a close genetic relationship between Fijian iguanas and desert iguanas from North America, suggesting a split between the two groups around 31 million years ago.
The researchers created a statistical model using that information and other tidbits about where iguanas live today and how they may spread. It suggested that the iguanas most likely floated to Fiji from North America.
“Given what we know now, their result is by far the most strongly supported,” said Kevin de Queiroz, an evolutionary biologist at the Smithsonian National Museum of Natural History, who was not involved with the new study.
The research was published Monday in the journal Proceedings of the National Academy of Sciences.
The journey from North America to Fiji could have taken a few months, but these desert iguanas would have been ideal passengers because they were adept at resisting dehydration and could have snacked on the plants underfoot.
“If you had to pick a vertebrate to survive a long trip on a raft across an ocean, iguanas would be the one,” said study author Simon Scarpetta from the University of San Francisco, in an email.
Many Fijian iguana species are endangered, and an invasive green iguana roams the islands today, said study author Robert Fisher of the United States Geological Survey. Figuring out where these creatures came from can equip scientists with the tools to better protect them in the future.
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