Genetic traces of extinct species of Galapagos tortoises have been found in their descendants living in the wild, Yale University announced this week. Now the researchers want to try to revive at least one of the species that have gone extinct by selectively breeding it out of the living hybrid population.
“Museum specimens and current molecular technology, coupled with 15 years of field work studying the tortoise population present now on the Galapagos archipelago has painted a new picture of the origins and future of some of the tortoises,” Yale evolutionary biologist Gisella Caccone and colleagues said.
When Darwin first visited the island of Floreana in 1835 and wrote about the giant tortoises, heavy human exploitation was already decimating the population, the scientists noted. Within a few decades, 4 of the 15 known species had disappeared. On some islands, tortoises were sacrificed for oil that was used to light the streetlights of Quito, Ecuador.
Others were taken as food or ballast for pirate and whaling ships.
Yale scientist and study co-author Nikos Poulakakis studying museum specimen for DNA samples.
Photo by Bernie Staggers/Courtesy Yale
“Matching museum specimens to current populations showed both distinct lineages and intermingled species,” the researchers said. “Of particular note, the team found tortoises on Volcano Wolf of the island Isabella — the furthest separated island of the archipelago — that had both the mitochondrial DNA and nuclear markers of the Floreana lineage.”
Perhaps some of the tortoises collected on Floreana for ship ballast were jettisoned on Isabella island, where they interbred, the scientists speculated.
Hybrids of the extinct Floreana tortoise line theoretically now could be bred, the researchers say, and over a long span, revive this species. An expedition on Volcano Wolf is planned in December 2008 to look for tortoises bearing the Floreana lineage.
Genes of the famous “Lonesome George” (photo right) were also found in the Volcano Wolf population, the researchers said. He is is believed to be the last surviving representative of the Galapagos Pinta Island tortoise species.
Photograph copyright Anders G. J. Rhodin, Chelonian Research Foundation
Work is also under way to completely sequence the tortoise genome to gain a better understanding of these animals.