Ecology

Not Extinct After All?

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Science  20 Jan 2012:
Vol. 335, Issue 6066, pp. 264
DOI: 10.1126/science.335.6066.264-a
CREDIT: ISTOCKPHOTO.COM

Extinction is forever, but determining when a species has truly become extinct is tricky, particularly for species that live in remote regions. In such regions, species are often categorized as extinct when no individuals have been seen for decades. This “absence of evidence” is imperfect, however, and occasionally individuals resurface. Up until now, such rediscoveries have been serendipitous and rare, but Garrick et al. now show that modern genetics has the potential to help facilitate such rediscoveries. Sampling of 20% of the giant tortoise population on Isabela Island in the Galápagos revealed a clear genetic signature of recent hybridization between the native species and pure members of a species from Floreana Island, thought to be extinct since the mid-1800s. Using rapidly evolving nuclear and mitochondrial markers, in conjunction with population simulations, they determined that 0.5% of the sampled individuals on Isabela had a 99% chance of having a pure Floreana parent. Furthermore, nearly a third of the Floreana descendents were less than 15 years old, which suggests that the hybridization events were the result of a healthy, reproductively active population of pure Floreana tortoises on Isabela.

Curr. Biol. 22, R10 (2012).

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