'Extinct' giant tortoise may live again

UBC Okanagan conservation geneticist Michael Russello and international team make genetic discovery that could see long-lost species restored through captive breeding

A species of giant tortoise thought to be extinct since the mid-1800s did not totally disappear after all. New genetic research has found living tortoises from the Pacific’s Galápagos archipelago that have remnants of an extinct genetic line -- a discovery that could lead to restoring the lost species Geochelone elephantopusthrough captive breeding.

G. elephantopus once thrived on the Galápagos island of Floreana, but was believed exterminated by intense harvesting. Using genetic material from museum specimens at Harvard University’s Museum of Comparative Zoology and the American Museum of Natural History, and from giant tortoises living on islands near Floreana, researchers discovered that the genetic line of G. elephantopus still exists in tortoises living on nearby 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," says Michael Russello, Assistant Professor and Acting Director of the Centre for Species at Risk and Habitat Studies (SARAHS) based at UBC Okanagan.

The research team, which included Russello and colleagues from Yale University, Australia's Macquarie University, and Italy’s University of Florence, published their findings this week in the prestigious journalProceedings of the National Academy of Sciences (USA).

"We show that the genetic line of G. elephantopus has not been completely extinguished and still exists in an intermixed population on Isabela,” Russello says. “With enough individuals to commence a serious captive breeding program, this finding may help reestablish a species that was thought to have gone extinct more than a century ago and illustrates the power of long-term genetic analysis and the critical role of museum specimens in conservation biology."

Giant tortoises, a prominent symbol of the Galápagos archipelago, illustrate the influence of geological history and natural selection on the diversification of organisms, Russello notes. Due to heavy human exploitation, four of the archipelago’s 15 known species have disappeared.

“The application of modern DNA techniques to museum specimens, combined with long-term study of a system, creates new opportunities for identifying the living remnants of extinct species in the wild,” says Russello.

With a population estimated at more than 20,000, the giant tortoises in a region of Isabela Island known as Volcano Wolf represent a potentially bountiful stock of individuals with which to initiate a captive breeding program, says Russello. Through captive breeding, targeted mate selection could help restore the genetic integrity of the Floreana Island population.

“As species continue to come under threat from human activities, even within World Heritage Sites such as the Galápagos, an increased depth of understanding will help refine conservation strategies to protect what remains – and potentially to resurrect what has been lost.”

Related links:

Ecological and Conservation Genomics Lab at UBC Okanagan

Centre for Species at Risk and Habitat Studies (SARAHS) at UBC Okanagan

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