Lone tortoise 'not last of kind'
By Paul Rincon
Science Reporter, BBC News
The giant Galapagos tortoise that became a conservation icon when it appeared he was the last of his kind is not so alone after all.
"Lonesome George" was thought to be the only survivor of a tortoise species native to the isle of Pinta.
Now, the journal Current Biology reports the discovery of a hybrid - the offspring from the union of a Pinta tortoise and another island species.
The "new" animal thus shares about half its genes in common with George.
Unfortunately for efforts to get George to reproduce, this hybrid tortoise, recently found on Isabela isle, is also a male.
Nonetheless, its discovery in a relatively small sample of tortoises raises fresh hope for the future of George's species (Geochelone abingdoni).
A more thorough sampling of the 2,000 tortoises living on Isabela could yet reveal a genetically pure Pinta tortoise, say the researchers.
Population revival?
But even if they did find one, getting George to mate with it could be an uphill struggle: he has a stubborn aversion to the opposite sex.
When George was placed in captivity at the Charles Darwin Research Station on the island of Santa Cruz, he was housed with two female tortoises from a species taken from Isabela.
After 35 years, he has failed to produce any offspring, turning his nose up at entire harems of female tortoises; though, admittedly, none of these tortoises has belonged to George's species.
Most giant tortoises on Isabela belong to the distinct species Geochelone becki instead.
Surprising find
The researchers, led by Michael Russello from the University of British Columbia Okanagan, Canada, took DNA samples from 89 of these animals and compared their genetic codes with those of other tortoises from the Galapagos that are held in a database.
The database includes DNA from six G. abingdoni specimens held in museums, and Lonesome George.
Genetic analysis revealed that one tortoise sampled on Isabela Island is clearly a first-generation hybrid between native tortoises from the islands of Isabela and Pinta.
"It's extraordinary. I, and everyone involved with George, always imagined that something like this could happen, but never thought it would," said Henry Nicholls, who has written a biography of the octogenarian tortoise called Lonesome George: The Life and Loves of a Conservation Icon.
"It is surprising to find a hybrid on Isabela. It raises questions about how it got there," he told the BBC News website.
Whaling link
According to Dr Nicholls, none of the prevailing sea currents would be capable of carrying tortoises from Pinta to Isabela.
But, Dr Nicholls added, any project to search for a pure Pinta tortoise on Isabela, or other hybrids, would be expensive and time-consuming.
"The continuing saga surrounding the search for a mate has positioned Lonesome George as a potent conservation icon, not just for Galapagos, but worldwide," said Dr Russello.
Upwards of 50,000 people visit George each year at his home on the Charles Darwin Research Station.
The collapse of the giant tortoise population on Pinta is thought to have been due in large part to whaling activities in the Pacific during the 18th and 19th Centuries.
Sailors would preferentially take female animals to store as food on their ships - the females of the species were smaller and easier targets in lowland areas during the egg-laying season.
By the middle of the 20th Century, only male giant tortoises were left on Pinta. George is thought to have been born in the 1920s.
Labels: Lone+tortoise +not+last+of+kind
posted by ... @ 3:32 PM
0 Comments:
Post a Comment
<< Home