'Extinct' humongous Galapagos tortoise could be making a comeback
After 150 years of being "extinct," a species of giant tortoise may be on the verge of a comeback tour, scientists report today (Jan. 9).
The researchers "found" the lost species, called聽Chelonoidis elephantopus, by analyzing the genome of a closely related species,聽Chelonoidis becki, which lives on Isabela Island, the largest of the Gal谩pagos Islands in the Pacific Ocean. The island lies about 200 miles (322 kilometers) from Floreana Island, where聽C. elephantopus聽was last spotted before disappearing, likely due to hunting by whalers, some 150 years ago.
The two species of gigantic tortoise, both living in the聽聽(famously studied by Charles Darwin), have different shaped shells. The shells of聽C. elephantopus聽on Floreana Island were saddle-shaped while tortoises on other islands, including聽C. becki, had domed-shaped shells. These giant tortoises can weigh nearly 900 pounds (408 kilograms) and reach almost 6 feet(1.8 meters) in length.
Finding hybrids
The researchers noticed in 2008 that some of the聽聽than domed shaped, and found that these were hybrid offspring from matings between the two species. They took samples for genetic analyses from 1,669 of the large tortoises on the island, about 20 percent of their population.
They found some snippets of the聽C. elephantopus聽genome in the population, and using a special computer model they analyzed how recently these genes would have entered the population. This would have happened when a living聽C. elephantopus聽mated with a聽C. becki聽鈥� and is indirect proof that at that time living聽C. elephantopus听别虫颈蝉迟别诲.
They found that 84 of the tortoises had genetic indicators that one of their parents was a聽C. elephantopus, 30 of which were less than 15 years of age. Given the 100-year lifespan of the tortoises the researchers say there is a good chance that their聽C. elephantopus聽parent would still be alive.
"To our knowledge, this is the first report of the rediscovery of a species by way of tracking the genetic footprints left in the genomes of its hybrid offspring," study researcher Ryan Garrick, who performed the work at Yale University, but is now assistant professor at the University of Mississippi, said in a statement. "These findings breathe new life into the conservation prospects for members of this flagship group."
Because of聽, the researchers estimate that at least 38聽C. elephantopus聽left behind hybrid descendants on the Gal谩pagos Islands, and many may still be alive.
Planning a comeback tour
If the researchers can find this hidden population, they could capture individuals to set up a breeding program to聽, the authors write in the paper published Jan. 9 in the journal Current Biology. They could even try to resuscitate the species from the genetic snippets found in聽C. becki.
"This is not just an academic exercise," study researcher Gisella Caccone, of Yale University, said in a statement. "If we can find these individuals, we can restore them to their island of origin. This is important as these animals are keystone species playing a crucial role in maintaining the ecological integrity of the island communities."
In an interesting twist, the researchers aren't sure how the聽聽would have gotten from Floreana Island to Isabela 鈥� they suggest the animals may have been brought to Isabela as food and then either thrown overboard or left on the shore.
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