Scientist Finds Extinct Tortoise Species in Galápagos Islands

In Galápagos, a previously believed extinct tortoise species has been discovered alive. Fernanda, named after her home on Fernandina Island, is the first of her species to be discovered in over a hundred years.

Fantastic Giant Tortoise

Only one specimen of the Fernandina Island Galápagos giant tortoise (Chelonoidis phantasticus), also known as the "fantastic giant tortoise," was collected in 1906. The discovery of a female tortoise on Fernandina Island in 2019 provided an opportunity to see if the species still exists. The two known Fernandina tortoises are members of the same species, genetically distinct from all others, according to Princeton's Stephen Gaughran.

Gaughran sequenced the genomes of both the living creature and the museum specimen to prove his point. He later compared them to the other 13 species of giant tortoises found on the islands of the Galapagos. He is a co-first author of a paper published in the current issue of Communications Biology that confirms the survival of Fernanda's species.

According to Peter Grant, Princeton's Class of 1877 Professor of Zoology, Emeritus and an emeritus professor of ecology and evolutionary biology who has spent more than 40 years studying evolution in the Galápagos Islands, it was thought for years that the original specimen collected in 1906 had been transplanted to the island because it was the only one of its kind. According to him, Fernanda appears to be one of the last people alive a century ago.

Gaughran, a postdoctoral research fellow in ecology and evolutionary biology at Princeton, shared that like many people, his initial suspicion was that Fernanda was not a native tortoise of Fernandina Island.

Gaughran sequenced Fernanda's entire genome and compared it to the genome he was able to recover from the specimen collected in 1906 to definitively determine her species. He also compared those two genomes to samples from the other 13 Galápagos tortoise species, including three individuals from each of the 12 living species and one from the extinct C. abingdonii.

Gaughran, who conducted the analyses after arriving at the university in February 2021, shared that they were surprised when they saw that Fernanda was very similar to the giant extinct tortoise species specimen that they found on that island more than a century ago. He pointed out that both of the said tortoises were very different from all of the other tortoises in the island.

Breeding Possibilities

In 2019, Gaughran worked in the lab of Yale University's Adalgisa Caccone, the paper's senior author. The discovery of one living specimen, according to Caccone, gives hope while also raising new questions, as many mysteries remain. She raised a few questions that their team might have, such as whether there are any more tortoises on Fernandina that could be taken in for breeding, the tortoises' colonization of Fernandina, their evolutionary relationship to the other giant Galápagos tortoises, and the importance of using museum collections to learn about the past.

Part of Gaughran's postdoc is developing a tool that analyzes DNA from ancient museum specimens so that it can be compared to modern samples.

His tool is adaptable enough to work on nearly any ancient artifact. Gaughran explained that the software doesn't care if the DNA comes from a seal, a tortoise, a human, or a Neanderthal; it is in the interpretation that it matters.

At Princeton, Gaughran is working with Andrea Graham and Bridgett vonHoldt to unravel the mysteries of pinniped evolution.

VonHoldt, an associate professor of ecology and evolutionary biology, said that Gaughran has such a curiosity for discovering the messages and codes tucked away in ancient remains as he has been collecting specimens from several hundred years old to a few thousand, and these hold the keys for understanding the history of when and how genomes changed over time.

Gaughran also led the effort to solve the mystery of Fernanda, the fantastic ghost tortoise rediscovered through molecular research, which surprised the team.