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 turtlesleatherback, flatback, green, hawksbill, loggerhead, Kemp's Ridley, and Olive Ridleyand 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 glassthey eat toxic spongeswhile 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 turtlethought by some to be a separate speciesfalls 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
|Contact: Kristin Elise Phillips|
American Museum of Natural History