Wednesday, 13 January 2010

The cunning of conservation genetics

Over in Galapagos, scientists have identified nine giant tortoises in captivity that appear to be descended from the long-extinct Floreana tortoise, a variety assumed to have disappeared more than 150 years ago.

Charles Darwin visited Floreana in 1835 though the island’s tortoises were already so thin on the ground that he didn’t run into any. If not already extinct, this species is thought to have gone that way just a few years after. But a few dozen specimens made it into museums and in 2008 geneticists at Yale University (and elsewhere) recovered ancient DNA from the remains of some 25 animals now housed at the Museum of Comparative Zoology at Harvard in Boston and the American Museum of Natural History in New York. This allowed them, in a paper published in Proceedings of the National Academy of Sciences, to describe the genetic makeup of this species, making it possible to begin the hunt for Floreana-like genes amongst living animals.

In that study, they identified several tortoises of Floreana ancestry on the Galapagos island of Isabela (though they only have the blood samples from these individuals and not the animals themselves). Now, in a paper out today in PLoS One, the same core team has combed through the DNA records of 156 captive tortoises of undocumented ancestry held at the Charles Darwin Research Station on the central island of Santa Cruz. Amongst them, they found nine individuals – six females and three males – with a good smattering of Floreana genes.

It’s almost a ready-made founder population. There are some snags, however. Not only would it be an expensive initiative, but it would be at least a decade before such a small captive operation began to churn out baby tortoises. By which time there would already be tortoises (of a necessarily different species) on Floreana, introduced to the island in the next few years as a part of the all-embracing Project Floreana.

Whatever happens, it’s another great example of how genetics is able to suggest serious conservation actions to which we would otherwise be completely ignorant.

My mind is on Galapagos matters just now because I am putting together the Spring/Summer issue of Galapagos News, the biannual charitable magazine for the Friends of Galapagos Organisations like the UK's Galapagos Conservation Trust and the US-based Galapagos Conservancy.

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