Habitat loss is one of the main threats facing Alabama red-bellied sliders, but it is not the only one. The researchers found that hybridization reduces the genetic uniqueness of the species.
Found only in river systems near Mobile, Alabama, turtles are considered endangered by the US Fish and Wildlife Service, in part due to environmental changes where they occur.
“The habitat is changing,” said Ylenia Chiari, an assistant professor at George Mason University in Virginia. “There are a lot of women getting killed for crossing some of the main roads.”
But the researchers weren’t very clear about the genetic health of the species (Pseudemys alabamensis). In fact, the entire genus is taxonomically a bit fuzzy. Species often hybridize and the boundaries between them are not well delineated.
For a study recently published in Ecology and evolution, Nickolas Moreno — Chiari’s master’s student when they were both at the University of Southern Alabama — set out to capture red-bellied turtles, also known as red-bellied cooters from the l ‘Alabama, across their range straddling the Alabama-Mississippi state line. Using a baited water trap that let turtles in but not out, Moreno searched areas where these turtles had been found historically, as well as other areas that appeared to have suitable habitat characteristics. He also tapped into a network of herpetology groups in Mississippi and Alabama on Facebook. They would help by bringing the turtles to the park offices, where wildlife managers would take blood samples and send them to Moreno.
Chiari and his team then began to analyze the genetic data of each sample obtained. They found that many Alabama red-bellied sliders hybridized with two related species, the river cooters (P. concinna) and coastal plains (P. floridana)—especially in the Mobile Tensaw Delta.
“The closer you get to Florida, the more concinna and Florida you find,” Chiari said.
The analysis also revealed that, even outside of hybridization, the Mississippi and Alabama populations are genetically distinct. This distinction could be due to the large bodies of water that have separated populations over time.
Chiari thinks a lack of mating options within their own species is likely to drive the hybridizations. DNA analysis revealed that some populations had very low genetic health, suggesting that they may not be doing as well.
The team also found a case of hybridization between an Alabama red-bellied turtle and a peninsular cooter (Pseudemys peninsularis), a species usually found deep in Florida, far from the range of Alabama’s red-bellied turtles. That case likely involved a released pet, Chiari said.
The pet trade is among the issues affecting the conservation of Alabama’s red-bellied turtles, alongside emerging concerns over chemical pollution and climate change. Rising temperatures are raising sea levels, which increases salt content in many brackish coastal areas and may make them less suitable for Alabama’s red-bellied turtles.
For Chiari, the study highlights the need for more focused conservation attention. Some wildlife sanctuaries are doing a good job of protecting these turtles, she said, but coordinated efforts are lacking across their range.
“It continues to not be a priority species in terms of stocks,” Chiari said.