When a small female turtle was spotted in 2019 on the isolated volcanic island of Fernandina in Ecuador’s Galapagos archipelago, the research team conducting the expedition was shocked.
Previously, only one other tortoise, a large solitary male, had been found there in 1906 by explorer Rollo Beck. Scientists thought this animal was the last of the “giant tortoise”, or Chelonoidis phantasticus, making the species extinct.
Then they found Fernanda.
“It was almost too good to be true that there was a turtle living in Fernandina. We were all so excited,” said Evelyn Jensen, a professor of molecular ecology at the University of Newcastle in the UK and co-author of a study published Thursday in the journal Communications Biology.
But when Fernanda was initially compared to the 1906 male specimen, held in a collection by the California Academy of Sciences, the two looked so different that scientists had to question whether they were the same species.
Some of the Galapagos tortoises have a domed upper shell, called a carapace, which resembles an upside-down bowl. But some species, like the male Fernandina, have a saddle-shaped carapace, in which the front of the upper shell above the head and neck arches upward, Jensen said.
“The arch in the shell gives these turtles a much greater range of motion with their necks, allowing them to reach higher to eat vegetation from the ground, so it may have evolved to have access to more food,” Jensen said.
The 1906 tortoise had an extreme saddle shape and a distinct flare at the edges, which is why it was nicknamed “phantasticus,” she said.
Fernanda’s status as a native phantasticus tortoise was in doubt because she had a smaller, smoother shell with none of this burning, although some questioned whether her growth had stunted and caused her features to be distorted.
Perhaps Fernanda was another species entirely, having floated from another island in the Galapagos archipelago. Together, these islands are home to 14 distinct species of giant tortoises. There may be another turtle yet to be identified, according to recent research.
The Fernandina tortoises are believed to have gone extinct due to the island’s active volcano, which has erupted around 25 times in the last two centuries. Lava flows likely reduced the small pockets of vegetation where the turtles could live and feed. The island is isolated along the western edge of the archipelago.
Reading between the genetic lines
To answer the question of Fernanda’s inheritance, the research team first sequenced Fernanda’s complete genome and then compared it with that of the 1906 tortoise, as well as the genomes of the other 13 species of Galapagos giant tortoises.
Fernanda’s DNA told an amazing story, much like the discovery of the turtle itself.
“We saw – honestly to my surprise – that Fernanda was very similar to the one they found on that island over 100 years ago, and both were very different from all the turtles on the other islands,” said co-author Stephen Gaughran, a geneticist and researcher at postdoctoral fellow at Princeton University in a statement.
The species thought to be extinct for 100 years finally had a proven living member.
The study’s senior author, Adalgisa Caccone, a researcher at Yale University, suggested that Fernanda could be a hybrid, created by a phantasticus mating with a now-extinct species that lived on the large neighboring island of Floreana. But more information is needed — specifically, finding more turtles in Fernandina.
There is evidence to suggest that there may be more phantasticus. Turtle droppings were seen on the island in 2014. Much of Fernandina has yet to be explored because extensive lava fields prevent anyone from entering the region.
“Fernandina is the tallest of the Galápagos Islands, geologically young, and is mostly a huge pile of irregular blocks of brown lava,” said co-author Peter Grant, professor emeritus of zoology and professor emeritus of ecology and evolutionary biology at Princeton University, in a statement.
“At lower altitudes, vegetation occurs in island-like clusters in a sea of freshly frozen lava. Fernanda was found in one of them, and there is evidence that some relatives may exist in these locations.”
Two expeditions to look for more turtles like Fernanda since her discovery in 2019 have been unsuccessful, but the National Park and the Galapagos Conservancy plan to carry out more campaigns in hopes of preserving the species.
Fernanda now lives at the park’s Fausto Llerena Giant Turtle Breeding Center, which serves as a rescue and breeding center. If more turtles like this are found, conservationists could start a captive breeding program to keep the species alive.
Both Fernanda and the 1906 tortoise have very high genetic diversity compared to other Galapagos tortoise species, Jensen said.
“This means that even if only a few other Fernandina tortoises were found and bred together, any hatchlings are unlikely to suffer negative impacts from inbreeding,” she said.
living on the edge
Galapagos tortoises can’t swim, so how did they get to the islands? Turns out they can float, which means hurricanes and storms can carry them.
About two million or three million years ago, a storm carried giant tortoises west of South America. Turtles interbred with each other on the islands where they landed, which made them evolve quickly. This cross resulted in 14 species, all descended from an ancestor.
The biggest difference in these tortoises is the shape of the shell, with domed tortoises living in humid environments at higher altitudes while saddle tortoises are in lower, drier ecosystems.
The number of Galapagos tortoises has declined by 85% to 90% since the early 1800s, according to the study, when whalers and pirates arrived in the archipelago.
As pirates attacked South American colonies and whalers hunted the region’s waters, they made giant tortoises their food source.
Turtles could live for months without food or water, so sailors filled the hulls of their ships with live turtles and then killed them along the way to get fresh meat, Jensen said.
And when the time came to lighten the load, the live turtles would be dumped into the ocean. Some floated and landed on different islands.
“Because of this, there are turtles present on some islands that are descendants of these abandoned turtles and have genetic identities that do not match the local species, although in many cases the abandoned turtles have hybridized with the local species,” Jensen said.
The 14 species are all on the International Union for Conservation of Nature’s Red List, ranging from vulnerable to extinct.
The tortoise, the largest cold-blooded terrestrial herbivore found on Earth, plays a critical role as an agent of stability in the Galapagos.
“The presence of turtles maintains a certain type of ecosystem and vegetation community that is natural to the islands,” Jensen said. “When turtles are taken out of the field, the environment changes and that affects all other species that depend on the ecosystem maintained by these animals.”
Fernanda, who the researchers estimate is over 50 years old, is a true survivor. It has survived volcanic eruptions and dwindling habitat in the face of lava flows. And whether she is the last of her species or just the beginning, Fernanda gives researchers hope that unseen species might still survive.
Source: CNN Brasil
