Giant tortoise returns from dead

Giant tortoise returns from the dead A giant tortoise which helped shape Darwin's ideas about evolution and was thought to have been extinct for 150 years may be living a secret life in the Galapagos Islands. Genetic clues suggest pure-bred members of the species  have recently interbred with some of their cousins.
Scientists found the genetic footprint of the species Chelonoidis elephantopus in the 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 is a high chance that many C. elephantopus individuals are still alive, scientists believe.
'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,' said lead researcher Dr Ryan Garrick, from the University of Mississippi in the US.
The genetic evidence, reported today in the journal Current Biology, 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 established on Floreana.
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 scientists took blood samples from more than 1,600 of the island's tortoises and compared their DNA with a genetic database of living and extinct tortoise 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,' said co-author Dr Gisella Caccone, from Yale University in the US.
'This is important as these animals are keystone species playing a crucial role in maintaining the ecological integrity of the island communities.'
Even if insufficient numbers of pure-bred tortoises can be found, intensive breeding of the hybrids might make it possible to resurrect the C. elephantopus species, say the scientists.