Lonesome George is not alone among Galápagos tortoises

Among flagship species for conservation, Lonesome George is perhaps the most renowned. Long thought to be the sole survivor of a species of giant Galápagos tortoise (Geochelone abingdoni), this conservation icon may not be alone for much longer. Researchers headed by investigators at Yale University report these findings in work published online on April 30th in the journal Current Biology, published by Cell Press.

Lonesome George originates from Pinta, an isolated, northerly island of Galápagos visited only occasionally by scientists and fishermen. In the late 1960s, it was noted that the tortoise population on this island had dwindled close to extinction. Indeed, in 1972 only a single male, Lonesome George, was found. He was immediately brought into captivity at the Charles Darwin Research Station on the island of Santa Cruz, where he is housed with two female tortoises from a species found on the neighboring island of Isabela. After 35 years, Lonesome George remains uninterested in passing on his unique genes and has failed to produce offspring. His status as the “rarest living creature” (Guinness Records) and the continuing saga surrounding the search for a mate have positioned Lonesome George as a potent conservation icon, not just for the Galápagos, but worldwide.

In the new work, Dr. Michael Russello (presently at the University of British Columbia Okanagan), Dr. Adalgisa Caccone, Dr. Jeffrey Powell, and colleagues, with the strong support and cooperation of the Galápagos National Park and Charles Darwin Research Station, studied the evolutionary history of a species of Galápagos tortoise (G. becki) on Isabela Island that was previously known to be genetically mixed. The study analyzed the distribution of genetic variation within two G. becki populations across the nuclear genome relative to a large database including individuals from all 11 extant species of Galápagos tortoises. The nearly extinct G. abingdoni on Pinta was added to the analysis for the first time by way of genetic-data collection from six museum specimens, also including Lonesome George. Population genetic analyses revealed that one tortoise sampled on Isabela Island is clearly a first-generation hybrid between the native tortoises from the islands of Isabela and Pinta. That is, this tortoise has half his genes in common with Lonesome George; unfortunately, it is a male. Given that there are well over 2,000 tortoises of G. becki on Isabela Island and a first-generation hybrid was detected in a very small subset of the population, there is hope that a more thorough sampling could reveal a genetically pure Pinta tortoise. In the event additional individuals of Pinta ancestry are discovered, a captive-breeding and repatriation program may be enacted for species recovery. These findings offer the potential for transforming the legacy of Lonesome George from an enduring symbol of rarity to a conservation success story.

The researchers include Michael A. Russello of University of British Columbia Okanagan in Kelowna, British Columbia; Luciano B. Beheregaray of Macquarie University in Sydney, Australia; James P. Gibbs of State University of New York in Syracuse, New York; Thomas Fritts of University of New Mexico in Albuquerque, New Mexico; Nathan Havill, Jeffrey R. Powell, and Adalgisa Caccone of Yale University in New Haven, Connecticut. This work was funded by a Bay Foundation grant to A.C. and M.A.R., and the Yale Institute for Biospheric Studies.

Russello et al.: “Lonesome George Is Not Alone among Galápagos Tortoises.” Publishing in Current Biology 17, R317-318, May 1, 2007. www.current-biology.com

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