April 14, 2014
Two New Alligator Snapping Turtle Species Announced, Some Face Localized Risks
Brett Smith for redOrbit.com - Your Universe Online
The report also indicated that the localized distribution of these species, which includes coastal rivers of the northern Gulf of Mexico, poses a significant threat to their continued survival.
“We have to be especially careful with our management of the Suwannee River species because this turtle exists only in that river and its tributaries,” said study author Travis Thomas, a Florida Fish and Wildlife Commission scientist, referring to a small river that winds through parts of Georgia and Florida. “If something catastrophic were to occur, such as a chemical spill or something that affects the entire river, it could potentially devastate this species. The turtle is extremely limited by its habitat. All it has is this river and it has nowhere else to go.”
Based on analyses of the fossil record and modern turtle morphology, study researchers revised the genus Macrochelys to include Macrochelys temminkii and the two newly-described species, Macrochelys apalachicolae and Macrochelys suwanniensis. Constrained to river systems that empty into the northern Gulf of Mexico, the species are split by geography, which triggered changes in genetics, according to the study team.
“M. temminkii is found in river drainages such as the Mississippi and Mobile, while M. apalachicolae is confined to the Apalachicola and other Panhandle rivers,” explained study author Kenneth Krysko, a herpetologist with the Florida Museum. “There are no alligator snapping turtles in the seven rivers between the Suwannee and Ochlockonee (Aucilla, Econfina, Fenholloway, Saint Marks, Steinhatchee, Wacissa and Wakulla). This gap creates a geographic isolation that has likely resulted in the Suwannee species being the most genetically and morphologically distinct of the three Macrochelys lineages.”
Surveys of the Suwannee River during the last three years have indicated M. suwanniensis populations are greater than previously imagined. However, the species’ success continues to be an issue because of its restricted range, according to the researchers.
To reach their conclusion, the scientists reviewed the fossil record, which reaches back 15 to 16 million years. They discovered morphological and genetic distinctions among the three species. Specific distinctions were noted in the carapace, or shell, which can be readily detected in both living and fossil examples.
“The western group (M. temminckii) is morphologically more primitive, but genetics testing suggests that the Suwannee snapper has a deeper divergence,” said study author Jason Bourque, a vertebrate paleontologist with the Florida Museum of Natural History. “When alligator snappers show up in the fossil record, they look a lot like modern alligator snappers. They do not start showing up in the fossil record until the early Miocene, but snapping turtles as a group go back to the late Cretaceous.”
Sometimes referred to as the “dinosaurs of the turtle world,” alligator snapping turtles can grow to 200 pounds and live almost 100 years. As apex predators, these turtles play a crucial role in their ecosystem, Thomas said.
The researchers said they hoped their work would inform efforts to maintain these turtles and their river ecosystems.