London: Scientists claim that a species of giant tortoise which influenced Charles Darwin's ideas about evolution and has been feared extinct for 150 years may still be alive in the Galapagos Islands in the Pacific Ocean.
A team in the US says that genetic clues suggest pure-bred members of the species have recently interbred with some of their cousins, after it found the genetic footprint of the species Chelonoidis elephantopus in DNA of 84 tortoises from Isabela Island, part of the Galapagos island chain.
Each of these hybrids must have had a parent that was one of the missing species. In 30 cases, breeding had taken place within the last 15 years. Since the lifespan of tortoises can exceed 100 years, there's a chance that many C. elephantopus individuals are still alive, say the scientists.
"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 (genetic codes) of its hybrid offspring," team leader Dr Ryan Garrick at the University of Mississippi, was quoted by the 'Daily Mail' as saying.
The genetic evidence suggests the tortoises inhabit the slopes of Wolf Volcano on Isabela Island, 200 miles from their ancestral home of Floreana Island.
During his historic voyage to the Galapagos in 1835, Charles Darwin noted that the shells of tortoises living on different islands had different shapes. The shells of C. elephantopus on Floreana were saddle-shaped while tortoises on other islands had dome-shaped shells. It was partly this observation that inspired Darwin's theory of natural selection. Not long after Darwin visited the Galapagos, C. elephantopus is thought to have been hunted into extinction by whalers and workers at a heating oil factory.
Early traces of the lost tortoise's DNA were first discovered in 11 members of the species C. becki living on Isabela Island. Then in 2008, researchers took blood samples from more than 1,600 of the island's tortoises and compared their DNA with genetic database of living and extinct species.
The analysis revealed genetic evidence of C. elephantopus in 84 Wolf Volcano tortoises. The giant tortoises may have been carried to Isabela Island on whaling ships. "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," said team member Dr Gisella Caccone at Yale University.
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