Science - Pink iguanas unseen by Darwin offer evolution clue

Michael Kahn

LONDON (Reuters) – Pink iguanas unknown to Charles Darwin during his visits to the Galapagos islands may provide evidence of species divergence far earlier than the English naturalist's famous finches, researchers said Monday.

The findings also for the first time describe the black-striped reptiles -- first seen in 1986 and only a few more times since -- as a new species, said Gabriele Gentile of the University Tor Vergata in Rome, who led the study.

They also add to understanding of the evolution of species on the remote islands, which remain much as they were millions of years ago and which inspired Darwin's theory of evolution by natural selection. Many of its species are found nowhere else.

"Despite the attention given to them, the Galapagos have not yet finished offering evolutionary novelties," Gentile and colleagues wrote in the Proceedings of the National Academy of Sciences.

"So far, this species is the only evidence of ancient diversification along the Galapagos land iguana lineage and documents one of the oldest events of divergence ever recorded in the Galapagos."

During Darwin's visit to the Galapagos in 1835 his observations of finch varieties with different-shaped beaks scattered across the archipelago's some 100 islands were a key element in his formulation of the principles of evolution.

His studies on how one type had evolved into several after a probable chance migration thousands of years earlier from the Latin American mainland lay at the heart of his major work "On the Origin of Species," published in 1859.

As the finches spread around the islands and their populations became cut off from each other, the birds adapted to the food locally available by developing beaks of a shape most suitable to harvest it, his research showed.

Darwin did not visit areas inhabited by the pink land iguana and so missed the species, whose existence suggests diversification in the Galapagos happened some five million years ago. That is far earlier than attributed to most other Galapagos species like the finches, Gentile said.

"We were not the first to see this form but we were the first to say what it is and that it is a new species," Gentile said in a telephone interview.

A genetic analysis showed that the pink reptile likely originated in the Galapagos and split from other iguana populations some five million years ago when the archipelago was still forming, the researchers said.

The creatures only seem to live near a single volcano at most 350,000 years old, which means the reptiles that grow longer than a meter and up to 12 kilograms must have at one time existed elsewhere in the Galapagos, Gentile said.

The researchers documented fewer than 40 of the iguanas over two years and Gentile said conservation efforts and funds are urgently needed to keep the species from dying off.

"We think the population is very small and there is a great risk of extinction," Gentile said.

(Reporting by Michael Kahn; editing by Jon Boyle)