Giant Tortoise 'Re-discovered'

Scientists working on the Galápagos Islands say they may have discovered a breeding population of a species of giant tortoise thought to be extinct since soon after Charles Darwin's visit to the islands in 1835.

Chelonoidis elephantopus, a species endemic to Floreana Island, were thought to be extinct despite eleven hybrid tortoises being detected on a neighbouring island which were thought to contain the genetic signatures of the 'extinct' specises.

Now scientists writing in the journal Current Biology say that C. elephantopus individuals must still be alive today based on "the genetic footprints left in the genomes of very recent hybrid offspring" on Isabela Island.
1669 totrtoises were sampled, with 84 exhibiting genotypes consistant with having one parent of the  'extinct' species. Given that C. elephantopus can live more than 100 years, it is likely that these parents are still alive and could be used to attempt a species recovery via captive breeding.

On his voyage to the Galapagos in 1835, Charles Darwin observed that the shells of tortoises living on different islands of the chain had different shapes – one of the observations that inspired his theory of natural selection. For instance, the shells of C. elephantopus on Floreana were saddle-shaped while tortoises on other islands had domed-shaped shells.

On Floreana, however, the tortoises disappeared because of hunting by whalers and workers at a heating oil factory that had been established on the island.

“This is not just an academic exercise,” said Gisella Caccone, senior research scientist in the Department of Ecology and Evolutionary Biology and senior author of the paper. “If we can find these individuals, we can restore them to their island of origin. This is important as these animals are keystone species playing a crucial role in maintaining the ecological integrity of the island communities.”

The international team of scientists suggest that, to their knowledge, this is the first rediscovery of a species by tracking the genetic footprints left in the genomes of its hybrid offspring.