Scientists have long puzzled over how iguanas, a group of lizards mostly found in the Americas, came to inhabit the isolated Pacific islands of Fiji and Tonga. For years, the leading explanation has been that progenitors of the island species must have rafted there, riding across the Pacific on a mat of vegetation or floating debris. But new research in the January issue of The American Naturalist suggests a more grounded explanation…
So Noonan and Sites tested the possibility that iguanas simply walked to the islands millions of years ago, before the islands broke off from Gondwana — the ancient supercontinent made up of present-day Africa, Australia, Antarctica and parts of Asia. If that’s the case, the island species would need to be old — very old. Using “molecular clock” analysis of living iguana DNA, Noonan and Sites found that, sure enough, the island lineages have been around for more than 60 million years — easily old enough to have been in the area when the islands were still connected via land bridges to Asia or Australia.
More on the iguana migration research.
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