Revealing the evolutionary history of threatened sea turtles

Oct 15, 2008
Green sea turtle (Chelonia mydas). Credit: D. Brumbaugh, CBC-AMNH

It's confirmed: Even though flatback turtles dine on fish, shrimp, and mollusks, they are closely related to primarily herbivorous green sea turtles. New genetic research carried out by Eugenia Naro-Maciel, a Marine Biodiversity Scientist at the Center for Biodiversity and Conservation at the American Museum of Natural History, and colleagues clarifies our understanding of the evolutionary relationships among all seven sea turtle species.

Naro-Maciel and colleagues used five nuclear DNA markers and two mitochondrial markers to test the evolutionary relationships of all species of marine turtles—leatherback, flatback, green, hawksbill, loggerhead, Kemp's Ridley, and Olive Ridley—and four 'outgroups,' or more distantly related animals. The results formed a well-supported phylogenetic tree, or cladogram, that tells the story of sea turtle evolution and is reported in the journal Molecular Phylogenetics and Evolution.

"The evolution of a specialized diet appears to have occurred three times, independently," says Naro-Maciel. "Many sea turtles are carnivorous generalists. However, hawksbills tend to have a diet of glass—they eat toxic sponges—while the leatherback consumes jellyfish and the green grazes mainly on algae or sea grass." Each of the species with specialized diets is positioned uniquely in the evolutionary tree.

Naro-Maciel and colleagues confirmed that one major group of sea turtles includes sister species flatback and green turtles (one carnivorous and the other herbivorous), while another clade is formed by the hawksbill, loggerhead, Kemp's Ridley and Olive Ridley turtles. The leatherback is confirmed as the most basal of all the sea turtles, and the Eastern Pacific green turtle—thought by some to be a separate species—falls within the green turtle species. The branches of this evolutionary tree can be calibrated with time using the new phylogeny and DNA data: Even though the ancestor of all sea turtles arose over 100 million years ago, the separation between the flatback and green turtles happened about 34 million years ago.

Determining the evolutionary relationships among sea turtles as well as the species identity of different populations of this highly migratory group of animals has implications for conservation. All sea turtles are included on the IUCN's Red List of Threatened Species, some of them as critically endangered, and an accurate understanding of this highly migratory group is important.

"These research results are another example of the importance of using systematics and taxonomy as a way to prioritize conservation efforts and strategies," says George Amato, Director of the Sackler Institute for Comparative Genomics at the Museum and an author of the article. "Only with these detailed studies can we better conserve the naturally occurring evolutionary novelty and patterns of genetic diversity for endangered species."

Source: American Museum of Natural History

Explore further: Diabetes drug found in freshwater is a potential cause of intersex fish

Related Stories

US govt sued over sea turtles snared in shrimp nets

Apr 15, 2015

Tens of thousands of endangered sea turtles die every year in the United States when they are inadvertently snared in shrimp nets, an environmental group alleges, filing a lawsuit Wednesday against the government.

Green sea turtles recover in Florida, Mexico

Mar 20, 2015

Long considered an endangered species, green sea turtles in Florida and Mexico have bounced back and officials said Friday they are seeking to change the turtles' protected status to "threatened."

Recommended for you

York's anti-malarial plant given Chinese approval

Apr 24, 2015

A new hybrid plant used in anti-malarial drug production, developed by scientists at the University of York's Centre for Novel Agricultural Products (CNAP), is now registered as a new variety in China.

The appeal of being anti-GMO

Apr 24, 2015

A team of Belgian philosophers and plant biotechnologists have turned to cognitive science to explain why opposition to genetically modified organisms (GMOs) has become so widespread, despite positive contributions ...

Micro fingers for arranging single cells

Apr 24, 2015

Functional analysis of a cell, which is the fundamental unit of life, is important for gaining new insights into medical and pharmaceutical fields. For efficiently studying cell functions, it is essential ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.