Galapagos tortoises, best known as the largest species in their family and as the creatures that helped inspire Charles Darwin to develop his theory of evolution, are actually two separate types of creatures, according to a new genetic analysis led by Yale University scientists.
According to research published Wednesday in the journal PLOS One, senior author Adalgisa “Gisella” Caccone, a research scientist in the Department of Ecology and Evolutionary Biology at Yale, found that several hundred tortoises living on one side of Santa Cruz Island were distinct from another group.
Dr. Caccone’s team explained that they had noticed differences in the carapaces (shells) of the two giant tortoise populations, but initially believed that these could be explained by variations within the same species. An in-depth genetic analysis proved otherwise, however, revealing the existence of two distinct species that just happened to share the same island.
“We analyzed a few fragments of the mitochondrial and nuclear DNA,” she told redOrbit via email, “and found that they are as genetically divergent from the species living on the western side of the same island as species living on different Galapagos islands. Moreover, the closest relative of this new species is a species from the neighboring island to the East.”
First new Galapagos tortoise species in 100 years (and there may be more!)
The species to which Dr. Caccone was referring is known as Chelonidis chatamensis, and it is native to the island of San Cristobal. More to the point, she added, the discovery of this new type of giant tortoise indicates than Santa Cruz was colonized by a pair of distinct lines of tortoises at different times – a discovery that may shed new light on the tortoise family as a whole.
Dr. Caccone told redOrbit that the discovery could provide new insight into the “evolutionary and ecological processes that produced the genetic and morphological diversity” that we see in this iconic group of creatures today. It also indicates that just because two different species live in relatively close proximity to one another, doesn’t mean they necessarily share common ancestry, nor is it a given that their divergence happened on the island.
The new species was given the name “donfaustoi” in honor of Fausto Llerena Sanchez, a retired ranger Galapagos National Park who worked tirelessly during his career to preserve the tortoises. She explained that the name was chosen in honor of Sanchez’s nickname, Don Fausto, and was “particularly appropriate” in light of “his contributions to preserving these species.”
This is the first species of tortoise ever to be names after a person from the Galapagos islands, according to Dr. Caccone. Furthermore, she pointed out that this is the first species of giant Galapagos tortoises to be identified and named by scientists in more than a century.
Is there a chance that there may still be other unique members of this tortoise family living on the islands?
“Possibly,” Dr. Caccone told redOrbit. “We are using genomic based tools to look at the genetic divergence of some tortoise populations from both extant and extinct ones and I think we have some more ‘surprises’ coming out. Stay tuned.”
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Feature Image: Washington Tapia
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