Alligator Snapping Turtle Split into Three Separate Species

Alligator snapping turtle / Garry Tucker, USFWS
Janet Fang 29 Apr 2014, 04:07
 
The alligator snapping turtle, Macrochelys temminckii, is only found in river systems that drain into the Gulf of Mexico. These magnificent animals are the largest river turtles in North America, and they’re often called “the dinosaurs of the turtle world.” New research shows that they’re actually three separate species. And despite the newfound species richness, they’re actually more endangered than we thought. 
 
With bear-like claws and beaked jaws, these 200-pound (90 kg), prehistoric-looking turtles have no natural enemies and can live for nearly a century. These largely sedentary behemoths sit on river bottoms waiting for food, wiggling a worm-like lure on their tongue to bait prey. They can be docile and slow, with algae growing on their spiky shells, but be warned: Having a finger caught in their jaws is like getting it stuck in a car door. 
 
Previous DNA analyses suggested that there could be enough variation across the animal’s range for three distinct assemblages: western, central, and eastern. To see if a taxonomic revision is in order, a team led by Travis Thomas from the University of Florida, Gainesville, analyzed the genetics of modern snappers (using blood samples from their tails), as well as their body shape and size. Then they looked to the fossil record, measuring skulls and shells of museum specimens dating back 16 million years. These confirmed their results: Each of the three lineages are genetically and morphologically distinct species. 
 
Turtles furthest west, in the river drainages of the Mississippi and Mobile rivers, will remain the alligator snapping turtle, Macrochelys temminckii. The new (central lineage) species will be called the Apalachicola alligator snapping turtle (Macrochelys apalachicolae), which lives in the Apalachicola and other panhandle rivers in Alabama, Georgia, and Florida. The Suwannee alligator snapping turtle (Macrochelys suwanniensis) from the eastern lineage lives only in the Suwannee River drainage in Florida and Georgia. 
 
There were deep divisions between each river. “Unlike common snappers, these turtles do not move from river to river,” study coauthor Joe Roman from the University of Vermont says in a UVM release. “They’re isolated and have been for millions of years, through many glacial ages.”
 
The most recent common ancestor of M. temminckii and M. apalachicolae existed 3.2 to 8.9 million years ago. They last shared a common ancestor with M. suwanniensis 5.5 to 13.4 million years ago, during the mid-Miocene to early Pliocene. 
 
While M. temminckii is morphologically the move primitive, the Suwannee snapper has a deeper divergence. There are no alligator snapping turtles in the seven rivers between the Suwannee and Ochlockonee --  a gap that created the isolation leading to the Suwannee snappers being the most distinct of the three. This species has a 4-inch (10 cm) notch in the rear of their shell. The other two species have short notches. 
 
So, it looks like we got two new turtles overnight! But the bad news is, these new species are more endangered than the previously recognized (singular) entity. Alligator snapping turtles used to be found north in the Midwest, but they were hit hard in the 1960s and 70s. They were hunted for soup, and with much of their range degraded, they’re now suffering a 95 percent decline. And now, each one is even rarer.
 
“The much-needed Endangered Species Act listing for these turtles” would help ensure their habitat is protected, says Collette Adkins Giese from the Center for Biological Diversity, which petitioned in 2012 to have these snappers protected under the act. “If we don’t act quickly to protect these dinosaurs of the turtle world, they, too, could go extinct.”
 
Thomas adds in a UF release: “If something catastrophic were to occur, such as a chemical spill or something that affects the entire river, it could potentially devastate [the Suwannee River] species. The turtle is extremely limited by its habitat. All it has is this river and it has nowhere else to go.”
 
The findings were published in Zootaxa this month. 
 
 
Image: Garry Tucker, USFWS via Creative Commons BY-CC 
 
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