Iguanas have long been known to raft on vegetation across the Caribbean, and historically they traveled 600 miles from Central America to the Galapagos Islands. However, recent research suggests that Fiji iguanas undertook a much longer journey.
A study by biologists from the University of California, Berkeley, and the University of San Francisco indicates that after 34 million years ago, Fiji iguanas reached the South Pacific islands following a 5,000-mile voyage from North America’s western coast. This is considered the longest transoceanic dispersal for any terrestrial vertebrate.
Overwater dispersal plays a key role in populating newly formed islands with plants and animals. Understanding these colonizations has intrigued scientists since Charles Darwin’s time. The study, soon to be published in the Proceedings of the National Academy of Sciences, aligns the arrival of Fiji iguana ancestors with volcanic island formation. Genetic divergence timing suggests their arrival at least 34 million years ago.
Lead author Simon Scarpetta stated, “We found that the Fiji iguanas are most closely related to the North American desert iguanas.” Co-author Jimmy McGuire added that alternative colonization models do not fit within this timeframe.
The journey would have been lengthy for an iguana or group of iguanas rafting across equatorial waters. Iguanas’ large size and herbivorous nature allow them to survive without food or water for extended periods. Uprooted trees could have provided sustenance during such a journey.
The suborder Iguania includes over 2,100 species like chameleons and horned lizards. The Iguanidae family comprises around 45 species living in regions such as Central America and the Galapagos Islands. However, Fiji iguanas remain isolated in the Pacific and face threats like habitat loss and invasive predators.
Biologists had speculated about ancestral iguanids traveling via various routes around the Pacific Rim but lacked conclusive evidence until now. Scarpetta’s comprehensive genetic analysis clarified their evolutionary lineage.
Scarpetta collected DNA sequences from over 200 specimens worldwide, revealing that Fiji iguanas are closely related to Dipsosaurus dorsalis from North America’s deserts. This finding challenges previous theories about their origin.
With this new analysis ruling out a South American origin, it appears likely that these iguanas coincidentally encountered emerging islands like Fiji soon after their formation.
Scarpetta continues his research on Iguanian lizards’ evolutionary relationships while other co-authors include experts from institutions such as UC Berkeley and Villanova University.
