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Ecoregion Description

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Species Richness

# of Endemic Species


144: US Southern Plains

Major Habitat Type:

temperate upland rivers


Text modified from Abell et al. 2000. Freshwater Ecoregions of North America: A Conservation Assessment. Island Press, Washington, DC, USA.


United States


This ecoregion covers southeastern Colorado, northeastern New Mexico, most of southern Kansas, western Oklahoma, and the panhandle of Texas. It is largely defined by the watersheds of three rivers—the upper portions of the Arkansas, the South Canadian, and the upper half of the Red.

Drainages flowing into:

The drainages of this ecoregion flow into the Mississippi River.

Main rivers or other water bodies:

The primary rivers include the upper part of the Arkansas, its largest tributary the South Canadian, and the upper half of the Red.


The ecoregion lies primarily within the Great Plains, but also a portion lies within the Rocky Mountains physiographic province. Elevation ranges from 144 m to over 4000 m on peaks along the western border.


The climate of the ecoregion is predominantly semiarid steppe, grading into humid subtropical to the east (Köppen 1936).

Terrestrial Habitats:

As one travels west to east vegetation grades from montane forests in the Rockies through short and mixed grasslands, and then to mixed forest-grassland mosaics at the border of the Ozarks. A majority of the ecoregion is grassland, with characteristic species including grama (Bouteloua spp.), buffalo grass (Buchloe dactyloides), little bluestem (Schyzachrium scoparium) and western wheatgrass (Agropyron smithii) (Ricketts et al. 1999).

Fish Fauna:

Species diversity in the Southern Plains is moderate, with diversity declining as one moves westward along the Arkansas and Red river courses. The upper portions harbor as little as one-half of the species found in the lower portions. A few species are gained, however, including the Red River pupfish (Cyprinodon rubrofluviatilis) found only in the upper Red River and Brazos drainages, plains killifish (Fundulus zebrinus), longnose dase (Rhinichthys cataractae) and flathead chub (Platygobio gracilis) (Cross et al. 1986).

Description of endemic fishes:

This ecoregion is not distinguished by particularly high endemism, with two endemic crayfish and two endemic fish. The fish are the prairie chub (Macrhybopsis australis) and peppered chub (Macrhybopsis tetranema).  

Other noteworthy aquatic biotic elements:

One distinctive feature of this semiarid region is the presence of heavily used aquifers, such as the famous Ogalalla Aquifer and the Arbuckle-Simpson Aquifer. The latter is relatively undeveloped, but critical subterranean and spring ecosystems in the area are threatened by pumping. The Oklahoma cave amphipod (Allocrangonyx pellucidus) is native to this region. This rare, endemic cave dweller is found only in the Arbuckle Mountains, and it depends on high water quality (The Nature Conservancy 1996b).

Another important freshwater ecosystem is the Cheyenne Bottoms Wetland. This is the largest system of permanent and ephemeral wetlands left in the state of Kansas. It serves not only as a critical habitat for aquatic species, it also functions as a stopover point for more than half the population of northward-migrating shorebirds of North America (U.S. Environmental Protection Agency 1995; The Nature Conservancy 1996a).

Justification for delineation:

Ecoregion boundaries are taken from Abell et al. (2000) and are based on subregions defined by Maxwell et al. (1995).


Abell, R., Olson, D., et al. (2000). "Freshwater ecoregions of North America" Washington, D.C.: Island Press.

Cross, F.B., R.L. Mayden and J.D. Stewart (1986)"Fishes in the western Mississippi drainage" In Hocutt, C.H.a.E.O.W. (Ed.). The zoogeography of North American freshwater fishes. (pp. 363-412) New York, NY: John Wiley & Sons.

Maxwell, J. R., Edwards, C. J., et al. (1995) "A hierarchical framework of aquatic ecological units in North America (Nearctic Zone)". St. Paul, MN. North Central Forest Experiment Station, USDA Forest Service.

Ricketts, Taylor H. Dinerstein Eric Olson David M. Loucks Colby J. (1999). "Terrestrial ecoregions of North America: A conservation assessment" Washington, D.C.: World Wildlife Fund.

The Nature, Conservancy (1996). "Cheyenne Bottoms Preserve"

The Nature, Conservancy (1996). "Troubled waters: Protecting our aquatic heritage" Arlington, Virginia, USA: Conservation Science.

The Nature, Conservancy (1996). "Preserve profile: Understanding the Clinch Valley bioreserve"

The Nature Conservancy World Wildlife Fund
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