Giant Galapagos tortoise species may not be extinct

Jack Billings
http://usatoday30.usatoday.com/news/world/environment/story/2012-01-06/galapagos-turtles-extinct/52467768/1
Published: Monday January 9, 2012
Source: USA Today
Author: Elizabeth Weise

Summary:
When Darwin visited the Galapagos islands in 1835, one of the animals that helped him develop his theory of evolution was the tortoise. One species he described was the Chelonoidis elephantopus which lived on Floreana Island and was thought to have gone extinct within 10 years of Darwin’s expedition due to whalers who hunted them for food. Recently, researchers did DNA testing on 1,600 tortoises on Isabela Island, and found 84 which were direct offspring of the Chelonoidis elephantopus among the Chelonoidis becki natives. They did DNA testing on the shells of tortoises in museums (where the only known Chelonoidis elephantopus were) to confirm that the 84 tortoises were in fact descendants of the Chelonoidis elephantopus. Because the length of these giant tortoises lives, these individuals could be the grand kids or even direct offspring of some the the tortoises Darwin saw on his expedition. This discovery wasn't made until now because Isabela Island was never settled by humans for its lack of fresh water and because of the difficulty of getting blood samples from these 400 pound tortoises. No pure-bred Chelonoidis elephantopus tortoises were found, but scientists plant to create a breeding program to back-cross the hybrids to make a population closer to full-blooded Floreanas that could be used to repopulate Floreana Island.

Relevance:
This connects to our units on heredity, molecular genetics, and the evolution of life. The article relates to heredity because it discusses selectively breeding the tortoises to obtain the pure-bred forms of the Chelonoidis elephantopus tortoises (which have bred with the native Isabela Island species). It relates to molecular genetics because the researchers had to use DNA testing to determine what species were on Isabela Island. It relates to evolution because (much like Darwin’s finches) these tortoises probably have a common ancestor from which they have adapted to their new, isolated environments. These isolated environments have cause them to evolve through genetic drift and natural selection. Gene flow is also shown when the two species of tortoises cross-breed on Isabela Island.