There are two species of Galapagos tortoise on Santa Cruz Island.
The Galapagos tortoises living on Santa Cruz island are two distinct species rather than a single species, according to new research published in PLOS One. Researchers had long thought that Chelonoidis porteri was the sole species on the island. But new research shows that Chelonoidis porteri lives on the west side and a new species, confirmed with DNA analysis, lives on the east side of the island. That tortoise, the newly named Eastern Santa Cruz tortoise (Chelonoidis donfaustoi) brings the total number of species of Galapagos tortoises to 11.
According to the research, 2,000 to 4,000 Chelonoidis porteri tortoises live on the southwestern slopes of Santa Cruz on about 60 square miles of land called La Reserva, but just 250 Chelonoidis donfaustoi tortoises occupy a 15 square mile section of land called Cerro Fatal. The two species don’t mingle and their carapaces are different in size and in shape.
The researchers say that the tortoises are spatially and evolutionarily distinct with the Reserva tortoises diverging around 1.74 million years ago and the Cerro Fatal tortoises diverging about 0.43 million years ago.
To confirm the tortoises are two distinct species, Adalgisa Caccone of Yale University examined mitochondrial and nuclear DNA that came from three museum specimens and found that the two tortoises on the same island are not that closely related. They determined that the Cerro Fatal tortoises are a closely related to the tortoises from San Cristobal Island and are grouped with the tortoises from Pinta, Española, and Santa Fe islands. The La Reserva species is closely related to the tortoises from the islands of Isabela, Floreana, Fernandina, and Pinzón in the Galapagos chain.
The new species is named after Fausto Llerena Sánchez, aka Don Fausto, who was a park ranger in the Galapagos National Park Directorate for 43 years.
John Virata keeps a western hognose snake, a ball python, two corn snakes, a kingsnake, and two leopard geckos. His first snake, a California kingsnake, was purchased for $5. His first pet reptile was a green anole that arrived in a small box via mail order. Follow him on Twitter @johnvirata