Previously, only one other turtle, a large solitary male, was found there in 1906 by explorer Rollo Beck. Scientists had thought that this animal was the last of the “giant fantastic tortoise”, or Chelonoidis phantasticus, making the species extinct.
Then they found Fernanda.
But when Fernanda was initially compared to the 1906 male specimen, housed in a collection at the California Academy of Sciences, the two looked so different that scientists had to wonder if 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 specimen, have a saddle-style carapace in which the front of the upper shell above the head and neck arches upward, Jensen said.
“The arch in the carapace gives these turtles a greater range of motion with their necks, allowing them to reach higher to eat vegetation above the ground, so it may have evolved to have access to more food,” Jensen said.
The 1906 tortoise had an extreme saddle-back shape and distinctive 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 carapace without any of these flares, although some wondered if her growth had been stunted and distorted her features.
The Fernandina tortoises were thought to have gone extinct due to the island’s active volcano, which has erupted about 25 times over the past two centuries. Lava flows likely reduced small pockets of vegetation where turtles could live and feed. The island is isolated along the western edge of the archipelago.
Read between genetic lines
To answer the question of Fernanda’s heritage, the research team first sequenced Fernanda’s full genome and then compared it to that of the 1906 tortoise as well as the genomes of the other 13 species of Galapagos giant tortoises. Fernanda’s DNA told a surprising 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 this island over 100 years ago, and both were very different from all the turtles on the other islands”, co-author Stephen Gaughran, a geneticist and postdoctoral researcher at Princeton University, said in a statement.
The species thought to be extinct for 100 years finally had a living member tested.
The study’s lead author, Adalgisa Caccone, a senior researcher at Yale University, suggested that Fernanda might be a hybrid, created by a fanciful mating with a now-extinct species that lived on the nearby Big Island of Floreana. But more information is needed – in particular, finding more turtles on Fernandina.
There is evidence to suggest there could be more phantasticus. Turtle droppings were spotted on the island as recently as 2014. Much of Fernandina has yet to be explored because vast lava fields prevent anyone from reaching its interior.
“Fernandina is the tallest of the Galapagos Islands, geologically young, and is mostly a huge pile of jagged blocks of brown lava,” said co-author Peter Grant, professor emeritus of zoology and professor emeritus of ecology and evolutionary biology. at Princeton University. statement. “At lower elevations, vegetation occurs in island-like clumps in a recently congealed sea of lava. Fernanda was found in one of these, and there is evidence that a few relatives may exist in other others.”
Two expeditions to search for more turtles like Fernanda since its discovery in 2019 have failed, but the Galapagos National Park and Galapagos Conservancy plan to conduct more campaigns in hopes of preserving the species.
Fernanda now lives at the park’s Fausto Llerena giant tortoise breeding center, which serves as a rescue and breeding center. If more turtles like Fernanda are discovered, conservationists could start a captive breeding program to keep her species alive. 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 have been found and mated, any offspring are unlikely to suffer the negative effects of inbreeding,” she said.
Living on the edge
Galapagos tortoises can’t swim, so how did they get to the islands in the first place? Turns out they can float, which means hurricanes and storms can carry them.
About 2 or 3 million years ago, a storm carried giant tortoises west from South America. The turtles bred with each other on the islands where they landed, causing them to evolve rapidly. This interbreeding resulted in 14 species, all of which descend from an ancestor.
The biggest difference between these turtles is their shell shape, with dome-shaped turtles living in humid environments at higher elevations, while saddleback turtles are found in lower, drier ecosystems.
According to the study, the number of Galapagos tortoises has declined by 85 to 90 percent since the early 1800s, when whalers and pirates first arrived in the archipelago. As pirates raided South American colonies and whalers hunted the surrounding 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 slaughtered them along the way to get fresh meat, Jensen said.
And when the time came to lighten the load, the live turtles would be thrown into the ocean. Some floated and landed on different islands.
“For this reason, there are turtles present on some islands that are the offspring 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 local species,” Jensen said.
All 14 species are 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 vital role as an agent of stability in the Galapagos.
“The presence of turtles maintains a certain type of ecosystem and plant community that is natural for islands,” Jensen said. “When the turtles are removed from the image, the environment changes, and this impacts all other species that depend on the ecosystem maintained by the turtles.”
Fernanda, estimated to be over 50, is a true survivor. It has survived volcanic eruptions and a shrinking habitat in the face of lava flows. And whether she’s the last of her kind or just the beginning, Fernanda gives researchers hope that unseen species may still survive.