Mississippi Piedmont Rivers & Streams - A Global Ecoregion

Some of the richest temperate freshwater ecosystems in the world

About the Area
The main rivers of the ecoregion are the Tennessee, Cumberland, and Ohio. This ecoregion arguably encompasses the richest temperate freshwater ecosystems in the world, as measured by the hundreds of highly localised endemic species that have evolved in ancient river systems.

The diversity of habitats, age, favourable climate, geologic stability of the region, and its escape from glaciation during the last Ice Age, have contributed to the evolution of a high diversity of animals.

There is an isolation created by the ridges, valleys, and the large number of rivers and streams in this region that results in localised endemism where some species live only in a very limited area or one body of water.

For example, Tennessee's Clinch River alone has 40 species of coexisting unionid mussels (20 other species have already been eliminated), with any relatively intact stream in this region supporting more mussels than all of Australia and Europe combined.

Local Species
Among the numerous species of imperiled endemic mussels are Dromedary pearlymussel (Dromus dromas), Birdwing pearlymussel (Lemiox rimosus), and Oyster mussel (Epioblasma capsaeformis).

Imperiled endemic fishes include Slackwater darter (Etheostoma boschungi), Duskytail darter (E. percnurum), Palezone shiner (Notropis albizonatus), Smoky madtom (Noturus baileyi), and Paddlefish (Polydon spathula).

This ecoregion is also home to numerous endemic salamanders, including the West Virginia spring salamander (Gyrinophilus subterraneus), Imitator salamander (Desmognathus imitator), Shovelnose salamander (Leurognathus marmoratus), Tennessee cave salamander (Gyrinophilus palleucus), and Streamside salamander (Ambyostoma barbouri). The Nashville crayfish (Orconectes shoupi) is endemic to this ecoregion as well.

Threats
Hydroelectric projects, channelisation, water withdrawals, pollution, and introduction of the nonnative zebra mussel (Dreissena polymorpha) and other exotics threaten the ecoregion. The Tennessee River system has more than 50 major dams, with many remaining freshwater species restricted to small segments of unaltered tributaries.

Resources
• NationalGeographic.com