New Species of Galapagos Tortoise Was Hiding in Plain Sight
October 22, 2015
An international team of scientists at Santa Cruz Island in the Galapagos chain have discovered a new species of giant tortoise that was hiding in plain sight among the island’s other tortoises. Given the scientific name Chelonoidis donfaustoi, the Eastern Santa Cruz tortoise is the first new species discovered at the famous Pacific island chain in more than a century. Scientists identified the new species from its genetic profile, which clearly distinguished it from similar tortoises that share the island.
The Galapagos are a chain of volcanic islands that lie in the Pacific Ocean about 600 miles (970 kilometers) west of Ecuador. Biologists have studied the unique wildlife of these islands ever since Charles Darwin visited in 1835. The rare animals and plants Darwin observed were instrumental in the development of his theory of evolution by means of natural selection. Among the best-known of the islands’ native residents are the giant tortoises—some weighing more than 500 pounds (230 kilograms). In fact, the Spanish word for the tortoises, galapagos, gave the islands their name. As the map shows, each of the islands have both Spanish and English names.
For more than 100 years, the tortoises of Santa Cruz Island had all been classified as a single species, Chelonoidis porter. One group of about 2,000 tortoises is found in the higher elevations of the island, areas which receive more rainfall. They are nearly indistinguishable physically from a smaller population of about 250 tortoises that live in the arid (dry), hot, lowland region known as Cerro Fatal (deadly hill). However, a genetic analysis of the two groups revealed that the Cerro Fatal group is a different and previously unknown species. Even more surprising, the scientists found the two Santa Cruz tortoises are not even that closely related. The Cerro Fatal tortoises’ closest relatives live on the nearby island of San Cristobal.
The discovery of this new species may help conservation efforts at the Galapagos, where population growth and agriculture have threatened many of the islands’ unique species. The discovery also forces scientists to examine the evolutionary history of the Galapagos tortoises more closely, since they can no longer assume that physically similar species are also closely related. Even after more than 100 years, there are new things to learn from the natural laboratory of the Galapagos Islands.