Hidden Biodiversity in Tennessee Rivers: A Q&A with University of Tennessee Researcher Gerald Dinkins

Many freshwater mussels in the Southeast are protected as threatened or endangered. New genetic research now reveals previously unknown species in the Tennessee River Basin—one of the most biologically diverse river systems in the world and home to more freshwater mussel species than anywhere else in North America. Recent research with key contributions from the University of Tennessee, Knoxville, used genetic analysis alongside traditional fieldwork and museum collections to formally describe two new species and identify a third that remains to be named. UT spoke with Gerald Dinkins, curator of malacology at UT's McClung Museum of Natural History and Culture and co-author of the paper, about the discovery, why the upper Tennessee River basin is uniquely diverse, and the collaborations that made the findings possible.

What did your team recently discover, and why is it significant?

We found that there are previously unrecognized species of freshwater mussels living in the Tennessee River drainage that had essentially been hiding within already described species for a very long time.

This group of mussels is particularly difficult to classify because individuals look very similar. Shell shape, color, and overall appearance don't vary much, and those physical traits are what biologists traditionally rely on for identification. As a result, these species went unnoticed for decades.

This discovery is significant because conservation protections, research funding, and habitat management decisions all depend on knowing exactly what species exist and where they occur.

A former UT undergraduate student led the effort to take a deeper look at this group using extensive fieldwork and genetic analysis. That work ultimately revealed two distinct species that have now been formally described in a peer-reviewed paper, along with evidence of a third species that remains unnamed.

The upper Tennessee River basin is described as having the highest mussel diversity in North America. Why is that?

A major reason for the Tennessee River basin's mussel diversity is geological history. The basin has been relatively undisturbed for a very long time. The last major ice sheets never reached this far south, so aquatic ecosystems here have had millions of years to diversify.

The basin also spans several different physiographic provinces, including the Blue Ridge, Valley and Ridge, Cumberland Plateau, and Coastal Plain. Each of these regions has its own geology and habitat types, and each supports species that are found nowhere else.

All of this creates a wide range of habitats—shoals, pools, glides, and long river reaches—that promote speciation and long-term survival.

Two of the newly recognized species have names tied closely to UT's history. Can you share more about that?

One of the species was named after Paul Parmalee, my predecessor and the first curator of the malacology collection at the University of Tennessee. He was instrumental in building the collection and mentoring students.

The second species had actually been named in the 1800s but was later lumped into another species. We resurrected that original name after determining it represented a distinct species. What makes that especially interesting is that it was originally named after a former UT president, Joseph Estabrook, who was also an avid amateur malacologist.

Estabrook collected freshwater mussels and snails from around East Tennessee and even from areas that are now part of UT's campus, sending specimens to scientists in the northeastern United States. Some of the locations he documented match where we now know this species occurs, making it a remarkable full-circle moment for UT.

What collaborations and partnerships across UT and the local community helped make this research possible?

Understanding the historical context of these species requires deep knowledge of UT's past. I relied heavily on colleagues with expertise in university history, including Thomas Broadhead and Betsey Creekmore.

The McClung Museum also played a key role as well. The holotypes and paratypes—the physical specimens that define each species—are housed there. In addition, preserved tissue samples are stored in the Department of Ecology and Evolutionary Biology's fish collection, making them available for future genetic research.

This research depended on strong collaboration across the scientific and conservation community. That includes partnerships with Virginia Tech, the Virginia Department of Natural Resources, the Tennessee Wildlife Resources Agency, the US Fish and Wildlife Service, and private landowners who allowed access to rivers and streams. Without those relationships, this work wouldn't have been possible.

What does this research say about the future of discovery in Tennessee's rivers?

It shows that there is still more to learn. Even in a river system that has been studied for a long time, new tools like genetic analysis are revealing hidden biodiversity. Discoveries like this remind us that biodiversity is often more complex than it appears—and that protecting these ecosystems requires understanding what's really living there.

More information:
www.mdpi.com/1424-2818/17/10/739, DOI is doi.org/10.3390/d17100739

Provided by University of Tennessee at Knoxville