We used to recollect there was just one species of giant tortoise hold out on Santa Cruz Island in the Galapagos archipelago . But after a thorough hereditary analysis , researchers discovered that the few hundred tortoises inhabit on the east side of the island belong to to a previously unknown mintage entirely freestanding fromChelonoidis porteriliving on the west side .
The fresh named eastern Santa Cruz tortoise ( Chelonoidis donfaustoi ) , describe inPLoS Onethis calendar week , brings the full giant Galapagos tortoise tally up to 12 .
A population of 2,000 to 4,000 jumbo tortoises hold up on the island ’s southwest slopes in a 156 - straight - klick ( 60 - solid - nautical mile ) sector called La Reserva . About 20 klick ( 12 miles ) to the eastern United States , a 2d population of just 250 tortoises engross a ironical 40 - square - km ( 15 - square - mile ) swath of state call up Cerro Fatal . The two group do n’t ruffle much and their domed upper shells ( call cuticle ) are of different sizing and shapes . Despite that , they were considered appendage of the same mintage . However , late studies have suggest that the two are spatially and evolutionarily distinct lineages , and they belike derived from separate colonization events from different source islands .
While there ’s a large amount of variant , multiple geomorphological measurement on several individuals are ask to distinguish them , Yale’sAdalgisa Cacconeexplained to IFLScience . Her squad move around to transmitted part . They examined mitochondrial and nuclear DNA extracted from three museum specimens : a skull ( pictured below , right ) and part of a carapace collect from the Cerro Fatal area , as well as theC. porteriholotype collected in 1902 , upon which the species verbal description was made . to boot , to estimate levels of their inherited diversity , the team looked at 70 mitochondrial DNA ( mtDNA ) sequence from Reserva tortoises and 51 from Cerro Fatal tortoises using previous studies . This combine dataset was compared with sequences from all Galapagos tortoise species – extinct and living – that have been discover by mtDNA study .
The eastern and western population on Santa Cruz , the researchers revealed , are as genetically distinct as different metal money living on different islands . In fact , they ’re not even that closely colligate .
Cerro Fatal tortoise are a baby species to those from San Cristóbal Island , and those two are grouped with tortoise from Pinta , Española , and Santa Fe island . Meanwhile , the stock from Reserva belongs in the same grouping as tortoises from Isabela , Floreana , Fernandina , and Pinzón Islands . Reserva tortoise are part of the archipelago ’s former pedigree , having diverged around 1.74 million years ago ; the much new Cerro Fatal tortoise diverged around 0.43 million long time ago .
The investigator named the fresh speciesChelonoidis donfaustoiafter Fausto Llerena Sánchez ( also known as Don Fausto ) , who had been a park ranger in the Galapagos National Park Directorate for 43 years . The squad also propose that the common name forChelonoidis porterishould be changed from simply Santa Cruz tortoise to the westerly Santa Cruz tortoise .
Recognizing the easterly Santa Cruz tortoise as a new species could help promote effort to protect them – especially with their smaller cooking stove , lower bit , and lower genetical variety . The team did find that 3 % of the tortoises are a mix of the two . They ’re likely the result of being transported by humanity , since the two metal money ’ range are now linked by an agrarian zone ( pictured in grey on the map ) that was created in the last century .
picture in the text : N. Poulakakis et al . , PLOS ONE 2015
UPDATED 2025-05-19 AT 3:00 PM ET
