Ever since Darwin first hinted at evolution after his 1835 trip to the Galapagos Islands, scientists have been eagerly following in his footsteps and exploring the unique endemic species that call these volcanic islands their home. October of 2015 will go down in history as another important date in Galapagos conservation, as a Yale research team has announced the identification of a new species of giant tortoise on Santa Cruz Island, making it the first new tortoise species identified in over a century.
Led by senior researcher Gisella Caccone, an evolutionary biologist and conservation geneticist from Yale, the team began its work in 2003, when herpetologist Tom Fritts recommended that they focus their attention towards a small population of tortoises that lived on eastern Santa Cruz and had a few morphological differences from the main Santa Cruz species, living on the western side of the island.
“I thought maybe they could be different populations of the same species,” said Caccone of the two Santa Cruz tortoise populations. “So I would expect some genetic differences between them if they lived [apart] in reservation for a while. But what I didn’t expect was that they were not even closely related to each other, because their closest [relatives] are from different islands.” According to Caccone, this introduces the surprising hypothesis that “the island of Santa Cruz was colonized twice, from two different islands, from two different lineages of tortoises that therefore are not each other’s closest relatives, [because] the divergence of these two species does not occur on Santa Cruz, but on different islands.” This discovery was just the most recent piece of a research project that Caccone has been heading up for over 20 years in the Galapagos Islands.
Looking forward, Caccone jokes that they will next be doing a “Lazarus project” of sorts, as they attempt to bring back certain species from extinction by finding and breeding hybrid tortoises that share DNA with species that have died out. “We have this interesting story,” she explains. “We have these species of DNA that are inside animals of a different species. And so the idea is to bring them [the hybrids] back to the [Breeding] Station and breed these animals that are hybrids (and some of them also are F1, meaning first generation, so 50% of their genome is from the extinct species). So we’ll breed them together […] It’s a really cool story.”