Yale Bulletin and Calendar

May 11, 2007|Volume 35, Number 28|Two-Week Issue

Scientists hope to find a suitable mate for Galápagos tortoise "Lonesome George," considered to be "the rarest living creature," in an effort to conserve the species.

Study of Galápagos tortoises' DNA
may locate mate for 'Lonesome George'

"Lonesome George," a giant Galápagos tortoise and conservation icon long thought to be the sole survivor of his species, may not be alone for much longer, according to a multinational team of researchers headed by investigators at Yale University.

New research led by biologists Adalgisa Caccone and Jeffrey Powell in Yale's Department of Ecology and Evolutionary Biology, with the strong support and cooperation of the Galápagos National Park and Charles Darwin Research Station, has identified a tortoise that is clearly a first-generation hybrid between the native tortoises from the islands of Isabela and Pinta. That means that this new tortoise has half its genes in common with Lonesome George.

According to the Guinness Book of World Records, Lonesome George -- a native of Pinta, an isolated northern island of the Galápagos -- is the "rarest living creature." By the late 1960s, it was noted that the tortoise population on this island, which is visited only occasionally by scientists and fishermen, had dwindled close to extinction, and in 1972, only this single male of the species Geochelone abingdoni was found.

Lonesome George 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.

"Even after 35 years, Lonesome George seems uninterested in passing on his unique genes and has failed to produce offspring," says lead author Michael Russello of the University of British Columbia-Okanagan, who began working with the tortoises as a postdoctoral fellow at Yale. "The continuing saga surrounding the search for a mate has positioned Lonesome George as a potent conservation icon, not just for Galápagos, but worldwide." Each year, upwards of 50,000 people visit the station where Lonesom George is kept.

This new study, published in Current Biology, gives a peek into the evolutionary history of a species of Galápagos tortoise (G. becki) -- previously known to be genetically mixed -- on the island of Isabela. The results were possible because advances in technology developed by these researchers made DNA from ancient or museum specimens useful for genetic analysis.

Population analyses of a large database including individuals from all 11 existing species of Galápagos tortoises was compared to the genetic variation within two of the G. becki populations. DNA data for the nearly extinct G. abingdoni species from Pinta was available for the first time from six museum specimens -- and from Lonesome George.

There are well over 2,000 tortoises of G. becki living on the volcanic Isabela Island, which has only two sites accessible from the sea. The research team collected samples from a total of 89 tortoises at two locations on the island. Because the subset of the population they sampled was so small, the researchers hope that thorough sampling will locate a genetically pure Pinta tortoise.

The authors speculate that, if additional individuals of pure Pinta ancestry are discovered, a captive breeding and repatriation program could be set up for species recovery.

"It will take a team of about 20 people about three to four weeks to do a first, exhaustive sampling and transmitter-tagging of the tortoises on the volcano," says Caccone. "Then once individuals of interest are found -- either hybrids with Pinta or pure Pinta animals -- an equivalent field expedition will have to be mounted to find the animals and bring them in captivity. But, it is a harsh environment with no local resources and funding such an operation will be costly."

According to Powell, "These findings offer the potential for transforming the legacy of Lonesome George from an enduring symbol of rarity to a conservation success story."

Other authors of the paper are Nathan Havill from Yale, Luciano B. Beheregaray from Macquarie University in Sydney, Australia, James P. Gibbs from the State University of New York at Syracuse and Thomas Fritts from the University of New Mexico. The research was supported by the Bay Foundation, the Yale Institute for Biospheric Studies and the National Geographic Society.

-- By Janet Rettig Emanuel

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