Boundaries

The watershed of the Tennessee River, which drains to the larger Mississippi Basin, defines this ecoregion. The majority of this area is centered in Tennessee; the river also drains parts of southwestern Kentucky, southwestern Virginia, western North Carolina, two disjunct areas in northern Georgia, northern Alabama, and the extreme northeastern corner of Mississippi.

Topography

The topography of the ecoregion is varied, rising from the Coastal Plain in the west to the Blue Ridge Mountains in the east. Tributaries drain the southern portion of the Highland Rim province, an upland area between 250 – 300 m elevation that encircles the Nashville Basin. East of the Cumberland Plateau lies the Ridge and Valley province, which is characterized by northeast-southwest trending long, even ridges and valleys. The Blue Ridge Mountains run parallel to the Ridge and Valley to the east and drain the high basins (600 – 800 m) within the ecoregion, with headwaters reaching elevations up to 1700 m (Starnes & Etnier 1986).

Freshwater habitats

From west to east, the Tennessee ecoregion traverses a number of physiographic provinces, creating a broad diversity of freshwater habitats. The lower Tennessee River basin drains a small portion of the coastal plain, and in this area streams are moderate to lower gradient. Swamps occur in the Big Sandy system, a major lower tributary to the Tennessee in the northwest corner of the ecoregion. Cave and spring habitats are abundant in the Highland Rim province, which covers most of the western half of the ecoregion. To the east of the Highland Rim is the Cumberland Plateau, and to the east of that is the Ridge and Valley province. Finally, the southeastern headwaters of the Tennessee drainage are found in the Blue Ridge province, where streams are typically high gradient and cold (Starnes & Etnier 1986).

Terrestrial habitats

Much of the ecoregion is covered in forest, particularly in the Jefferson, Pisgah, Cherokee, Nantahala, and Chattahoochee National Forests. Agriculture also accounts for a major land use, with most agricultural land used for pasture (Hampson 1995).

Description of endemic fishes

These endemics are made up of a large number of darters, as well as minnows, chubs, madtom catfishes, a cave-fish, pygmy sunfish and sculpins (Starnes & Etnier 1986). Of the many physiographic provinces in this ecoregion, the Highland Rim and Ridge and Valley tend to support the largest numbers of fish species. Many species with the most restricted ranges are found where provinces meet and overlap; for instance, the palezone shiner (Notropis sp.), smoky madtom (Noturus baileyi), and duskytail darter (Etheostoma sp.) all apparently require habitat created by the combination of features in two provinces (Starnes & Etnier 1986). New species of fish continue to be discovered and described in this ecoregion, despite fairly extensive historical study of the region’s fauna (Starnes & Etnier 1986; Burr pers. comm).

Justification for delineation

Ecoregion boundaries are modified from Abell et al. (2000), which based its units on subregions defined by Maxwell et al. (1995). Modifications to this ecoregion were made following recommendations from the Endangered Species Committee of the American Fisheries Society. Based on faunal data from Hocutt & Wiley (1986), the Endangered Species Committee decided there was a significant number of species exclusively endemic to the Cumberland [151] and Tennessee [152] drainages to warrant separate ecoregions.