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Maybe Not So Extinct After All

The giant tortoise Floreana, once a lumbering denizen of the Galapagos Islands, was thought to be extinct by about 1835. But now, researchers have found what seems to be genetic traces of Floreana in other tortoise species, suggesting that Floreana might not be so extinct after all, says Not Exactly Rocket Science's Ed Yong. Led by Yale University's Adalgisa Caccone, an international team of researchers in 2008 found that some tortoises on the largest of the Galapagos' islands, Isabela, were genetically different from other tortoises, Yong says. When the researchers sequenced the DNA of these renegade reptiles, they found that it partially matched the DNA of Floreana. "The discovery suggested that the Floreana line hadn't been snuffed out entirely. Pirates and traders often moved the tortoises from one island to another, so it's entirely plausible that Floreana individuals could have ended up on Isabela," Yong adds. "Perhaps they live there still, interbreeding with the locals to produce a hybrid population."

In a more recent Current Biology study, the researchers say they've found even more evidence of Floreana's survival. They sampled DNA from nearly 1,700 tortoises at the mountain peak in Isabela — about a fifth of the total number of animals there — about found that 84 of them were first-generation hybrids. This means they all had a Floreana as a parent, Yong says. Twenty-six of the 84 even had Floreana mitochondrial DNA. Extinct species have been rediscovered before — so-called "Lazarus species." And there are "cryptic species" — what was thought to be one species, but turns out to be two or three. But this study, Yong says, marks the first time that the two are combined — an apparently extinct species still genetically alive in descendants of another species. "It's a cryptic Lazarus species!" he adds.

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