Researchers Figured Out How Iguanas Crossed The Ocean And Landed In Fiji
Around 34 million years ago, iguanas traveled one-fifth of the way around the world from the western coast of North America to Fiji by clinging to floating vegetation. It was the longest-known transoceanic voyage of any terrestrial species.
Researchers at the University of California, Berkeley and the University of San Francisco believe the iguanas made the 5,000-mile journey by clinging to floating vegetation, arriving in Fiji shortly after the South Pacific Islands were formed.
“You could imagine some kind of cyclone knocking over trees where there were a bunch of iguanas and maybe their eggs, and then they caught the ocean currents and rafted over,” said Simon Scarpetta, the lead author of the study and an assistant professor of environmental science at the University of San Francisco.
Their long trip is referred to as overwater dispersal. It is the main way that new islands get populated by animals and plants. The bright green lizards on Fiji are the only iguanas outside of the Western Hemisphere.
In a new genetic analysis, the researchers found that Fiji’s iguanas are more closely related to their cousins in the Western Hemisphere than previously thought. They diverged from their closest relatives, the North American desert iguanas.
“That they reached Fiji directly from North America seems crazy,” said Jimmy McGuire, a co-author of the study and a professor of integrative biology at UC Berkeley.
“But alternative methods involving colonization from adjacent land areas don’t really work for the timeframe since we know that they arrived in Fiji within the last 34 million years or so. This suggests that as soon as land appeared where Fiji now resides, these iguanas may have colonized it. Regardless of the actual timing of the dispersal, the event itself was spectacular.”
Today, sailors can reach Fiji from California in about a month, but it would’ve taken a group of iguanas a lot longer to float across the waves to Fiji and Tonga.
Iguanas are large and herbivorous, and they can survive long periods of time without food or water. If their rafts were made of uprooted trees, that would’ve provided a source of food for them.
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Overall, there are more than 2,100 species in the suborder Iguania, which includes chameleons, bearded dragons, and horned lizards.
There are 45 species of Iguanidae, the Western Hemisphere family of lizards, living in the Caribbean and the tropical, subtropical, and desert regions of North, Central, and South America.
The Fiji iguanas are isolated in the middle of the Pacific. The four species on Fiji and Tonga are considered to be endangered because of habitat loss, predation by invasive rats, and being illegally captured and sold into the exotic pet trade.
The new research into the origins of Fiji iguanas rely on a genome-wide DNA sequence collected from over 200 iguana specimens from museums around the world.
The analysis determined that the Fiji lineage, Brachylophus, is most closely related to those in the Diposaurus genus, which live in the deserts of North America.
Since these desert iguanas are well-adapted to extreme heat, they were the most likely to survive the journey across the Pacific.
The new study was published in PNAS.
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