Extinct Galapagos Tortoise Could Be Resurrected
By Anne Minard
for National Geographic News
|September 23, 2008|
A giant tortoise species from the Galápagos Islands thought to be extinct since the 1800s may not be gone after all, according to new research findings.
The very same history that wiped out its populations may have inadvertently saved it.
Scientists have discovered that genes from the Floreana tortoise, which Charles Darwin studied on his visits to Floreana Island in 1835, can be found in modern Galápagos tortoises.
Experts now believe a concentrated breeding program could resurrect the species.
Yale University researchers have been visiting the islands, off the coast of Ecuador, since the mid-1990s, when they first noticed tortoises with mixed appearances—some of them strikingly similar to supposedly extinct species.
The 15-year effort was partially funded by the National Geographic Society's Committee for Research and Exploration. (National Geographic News is owned by the National Geographic Society.)
The results appear in this week's issue of the Proceedings of the National Academy of Sciences.
Food and Lamp Oil
Tortoises on the Galápagos Islands helped fuel evolutionary biologist Charles Darwin's theory of natural selection.
He found different tortoise sizes and shapes corresponded to survival in various types of island habitat.
Some of the reptile species are rounded or dome-shaped, while others are saddlebacked, with the front part of their shells elevated. Past research has suggested the saddlebacked adaptation is for feeding on taller plants in dry habitats.
When Darwin visited the Galápagos Islands in 1835, he noticed that the tortoises were being heavily exploited as food. One species in particular—a saddlebacked variety from the island of Floreana—was also being hunted for its oil, which was valued as lantern fuel.
Four of the fifteen historic tortoise species disappeared from the islands. The Floreana species "was believed to have been exterminated within 15 years of Darwin's historic visit," the study said.
But the exploitation had a silver lining, said lead author Adalgisa Caccone of Yale University.
Whaling ships would often take on so many whales and other sea creatures—including tortoises—that they would have to offload some of their catch on or near the islands. In this way, many of the tortoises ended up as transplants on new islands, where they found familiar habitats.
The practice, Caccone said, "allowed by chance the survival of these genes that otherwise would have been lost forever."
Turtle Mother Lode?
in 1994 Caccone and her colleagues saw tortoises from an area called Volcano Wolf, on Isabela Island. The animals were primarily dome-shaped, with a few saddlebacked varieties in the mix.
The researchers began meticulously combing Volcano Wolf specimens' genes for identifiers unique to the extinct Floreana species.
They found that the population on Floreana was in an evolutionary class by itself.
They also found genes in a few of the Volcano Wolf animals that were closer to that singular Floreana saddlebacked line than to the rest of the turtles on Isabela Island.
"Surprisingly, we found that these 'non-native' tortoises from Isabela are of recent Floreana ancestry and closely match the genetic data provided by the museum specimens," the study authors wrote.
Michel Milinkovitch is a tortoise expert at the University of Geneva in Switzerland who was not involved with the new study. He called it a nice demonstration of the use of molecular markers to unravel historical information.
"Theoretically, it would be possible to regenerate a pure Floreana genome, but it would require many generations of controlled breeding and the use of many molecular markers to guide/assist this breeding," Milinkovitch wrote in an email.
"It would obviously be easier with mice than giant tortoises, unfortunately."
Caccone agrees that such a breeding program will be tough, but she says she's eager to try.
In December, she and other researchers will team up with Galápagos National Park rangers to canvass the Volcano Wolf population—thought to number between 1,000 and 8,000—for blood samples. They'll put unique transmitters on each individual, so they have a way to find and recapture the ones that reveal hidden Floreana genes.
Caccone said she's excited about the possibility of bringing back one of the world's missing animals.
"This is the first case in which we could bring back from extinction a species that is gone," she said.
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