Rather than the two populations being a variation of the Chelonoidis porteri Galápagos tortoise, a genetic analysis has revealed that there are two tortoise species present on Santa Cruz Island.
The taxonomy of Galápagos tortoises has mostly been based on their morphology and the island where they live. But, researchers led by Yale University's Adalgisa Caccone report in PLOS One on their analyses of DNA from living Santa Cruz tortoises, from both the eastern and western populations, and museum specimens. Based on the tortoises' mtDNA, the researchers developed a phylogenetic tree. They also examined about a dozen nuclear microsatellite loci.
These two populations, they found, are genetically distinct and are not, as Caccone tells the New York Times, each other's sister species. Instead, the newly identified species is more closely related to tortoises from San Cristóbal, suggesting that tortoises colonized Santa Cruz twice.
The researchers dubbed this new species Chelonoidis donfaustoi after Fausto Llerena Sánchez, a 75-year-old park ranger there who recently retired.
"This guy dedicated his life to them," Caccone tells Nature News. "All the other [tortoise] species are named by scientists for scientists or explorers, but no species has been named after a person from Ecuador."