It’s been hiding in plain sight since the discovery of the Chelonoidis porteri species over 100 years ago. However, the new Galápagos tortoise species takes scientists by surprise.
Living on the Santa Cruz island for a long while, two very similar giant tortoise populations split their territory. On the east side of the island, the Cerro Fatal giant tortoises never meet with their southwest and west neighbors, the Reserva giant tortoises. Although they look strikingly similar, new research reveals that in fact they have less in common than previously thought. Until recently labeled under the same species, the Chelonoidis porteri, the giant tortoises have been separated.
Adalgisa Caccone, evolutionary biologist and senior researcher at Yale and her team put the DNA of the Cerro Fatal and the Reserva tortoises to a test. Analyzing mitochondrial DNA and repetitive nuclear DNA from both populations, an unexpected discovery came about.
This is the reason why the new Galápagos tortoise species takes scientists by surprise. Reserva giant tortoises and slightly smaller Cerro Fatal tortoises were found to be part of two different species. Regardless of their strikingly similar aspect, they also seem to be related more to tortoise species inhabiting other islands of the Galápagos rather than each to another.
After the unexpected discovery, the team needed to understand which species would remain known as the Chelonoidis porteri. The other would have to be included a new denomination. Thus, the team took up some more work. Looking at museum specimens and type specimens of both the Cerro Fatal giant tortoises and Reserva giant tortoises, the researchers got an idea of which one would be newer species. Type specimens date back to the beginning of the 20th century, when the Chelonoidis porteri species was discovered.
To no avail, the DNA of the type specimen was mixed. The mitochondrial DNA was traced to the Cerro Fatal giant tortoises. However, the nuclear DNA belonged to the Reserva giant tortoise. To settle the matter, taxonomy experts were brought in. In their opinion, nuclear DNA trumps mitochondrial DNA.
As such, the Cerro Fatal giant tortoise population has a brand new species name. Titled after Fausto Llerena Sánchez, the species is called Chelonoidis donfaustoi. The findings are published in the PLOS ONE journal.
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