Giant tortoise on the Galapagos Island of Santa Cruz stick to their own sides. One group hangs out on the east side, and the other likes the west and southwest. Scientists long believed they were all members of the same crowd until they investigated a bit deeper and found a new species hiding among them.
The east side giant tortoises were called the Cerro Fatal, and the west side ones were given the name Reserva. They look nearly identical and both have domed shells, National Geographic reported. So they were lumped together into Chelonoidis porteri.
Only when scientists measured them and took a peek at their genes did they learn they aren’t the same species at all — the east side guys, Cerro Fatal, are distinctive. In other words, looks can be deceiving.
“As different as they are genetically, it’s not obvious to the eye,” said vertebrate conservation biologist James Gibbs.
And oddly, the two species of tortoise are more related to cousins on other islands than they are to each other.
According to the Telegraph, scientists began to think they had a new animal back in 2002; their shell formation made them wonder if they were all members of the same group. They tested some genetic samples and, in 2005, results hinted they may have found something new.
Recently, a Yale research team analyzed the repetitive nuclear and mitochondrial DNA of a giant tortoise from each population and confirmed they were unique and closely related to creatures on other islands.
An expert named Peter Paul van Dijk told the New York Times that this research hints that the Cerro Fatal group came to Santa Cruz during a “once-in-a-decade or once-in-a-century extreme weather event,” like a hurricane.
Then came the question — which giant tortoise gets christened with a new name? Scientists examined museum specimens, including a so-called type specimen of C. porteri collected in the early 20th century.
They found it was a hybrid, with the nuclear DNA from the west side population and mitochondrial DNA from the east. This was also the first example of interbreeding they’d ever found. In the end, the giant tortoise with the nuclear DNA lost the name contest and shall remain Reserva.
Cerro Fatal, the smaller of the two groups, now gets the name Chelonoidis donfaustoi, an homage to a man who took care of endangered tortoises, named Fausto Llerena Sánchez, who is now retired.
“Now the genetics has put some real evidence that says the simple explanations don’t hold, that some of the islands have tortoises that arrived at different times from different islands,” Oliver Ryder, director of genetics at the San Diego, told the Times. “The recognition of this separate evolutionary history I think will be very important.”
At least one scientist isn’t buying it. Daniel Mulcahy at the Smithsonian said the hybridization and the two groups’ striking similarity make him skeptical that they’re two different species. But researchers who made the discovery remain convinced and they say that this information will help conservation groups protect both populations.
“Now when they’re going to manage these populations, they can manage them more effectively by having a better understanding of their evolutionary history and where the different species are,” said biodiversity researcher James Parham.
The new C. donfaustoi are only 250 strong and the C. porteri are now down 250 members; that group also lives in a more restricted area. Researchers now believe 15 giant tortoise species lived on the islands, four of whom are extinct.
[Photo by Anna Azimi/ Shutterstock]