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Ecoregion Description

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Species Richness

# of Endemic Species


147: Ozark Highlands

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 extends from southern Missouri into northern Arkansas. The Ozark Highlands ecoregion is part of the western Mississippi drainage but is distinctive because of its relative biogeographical isolation. It is a region of high gradient headwater streams surrounded by coastal plains and prairie.

Drainages flowing into:

This ecoregion drains the portion of the Arkansas River from the Ozark Highlands. The Arkansas is the second largest tributary of the Mississippi River.

Main rivers or other water bodies:

The Ozark Highlands is largely defined by the watersheds of the middle portion of the Arkansas River and the White River, including its tributary the Black River. Other major rivers bordering the ecoregion include the Missouri to the north and the Mississippi to the east.


The Ozarks form a deeply dissected plateau comprised of four physiographic sections – the Salem Plateau, Springfield Plateau, St. Francois Mountains and Boston Mountains. Topography ranges from gently rolling hills to rugged areas with steep escarpments and low mountains with elevations up to 925 m (TNC-OEAS 2003). Karst features such as sinkholes, springs and caves are common.


Mean annual precipitation ranges from 1020 to 1220 mm, and mean annual temperature is 13 to 16 oC (McNab & Avers 1994).

Freshwater habitats:

The Ozark Highlands contain a diversity of freshwater habitats, including fens, sinkholes and springs, which feed the clear headwaters of larger, free-flowing streams (TNC-OEAS 2003). Many of these habitats served as refugia during periods of glacial maximas (Hocutt 1977).

Terrestrial Habitats:

Terrestrial habitats in the ecoregion range from tallgrass prairie to oak-hickory forest, oak-hickory-pine forest, and cedar glades (McNab & Avers 1994).

Fish Fauna:

The Ozarks are home to a unique assemblage of species, including relict populations of more northerly species, such as the Ozark minnow (Notropis nubilus) and silver redhorse (Moxostoma anisurum) (Cross et al. 1986). The ecoregion also shares a number of species with the Cumberland [151] and Tennessee [152] drainages, such as the banded sculpin (Cottus carolinae)(Starnes & Etnier 1986). These species likely had a continuous distribution prior to the last glaciation, but were disconnected into refugia as glaciers advanced southward (Burr & Page 1986).

Description of endemic fishes:

Geographic isolation and age have contributed to a high level of endemism in fish, crayfish and mussels, many of which are found in karst habitats and streams. The Ozarks contain 10 endemic fish species, including a number of darters, the Ozark shiner (Notropus ozarcanus), Ozark chub (Erimystax harryi), and two madtoms (Noturus albater and N. flavater) (TNC-OEAS 2003).

Other noteworthy aquatic biotic elements:

The Ozark Highlands are remarkable for their populations of aquatic herpetofauna, many of which are restricted to the confines of the Ozark Plateau and the adjacent Ouachita Highlands [145]. In all, there are over 40 species of salamanders, frogs, and aquatic snakes in this ecoregion. Though none are found exclusively in the Highlands, several are near-endemics, such as Strecker’s chorus frog (Pseudacris streckeri) and the ringed salamander (Ambystoma annulatum).

Both the Ozark Highlands and the Ouachita Highlands [145] ecoregions are remarkable for their rich crayfish fauna. Particularly distinctive are the populations of hypogean crayfish present in the extensive caves of the region, such as the Salem Cave crayfish (Cambarus hubrichti) and the bristly cave crayfish (Cambarus setosus). Both these animals are slimmer and smaller than their epigean cousins, and almost completely lack pigment (Laws 1998). The Ozark Highlands also hosts 3 endemic mussels.

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.

Burr, B. M.,Page, L. M. (1986)"Zoogeography of fishes of the lower Ohio-upper Mississippi Basin" In Hocutt, C.H.;Wiley, E.O. (Ed.). The zoogeography of North American freshwater fishes. (pp. 287-324) New York, New York, USA: Wiley.

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.

Laws, J. (1998). "Ozark caving: Cave Pod People"

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.

McNab, W. H.,Avers, P. E. (1994) "Ecological subregions of the United States". U.S. Forest Service, ECOMAP Team, WO-WSA-5. Online.

Robison, H. W. (1986)"Zoogeographic implications of the Mississippi River Basin" In Hocutt, C.H.;Wiley, E.O. (Ed.). The zoogeography of North American freshwater fishes. (pp. 267-285) New York, New York, USA: Wiley.

Starnes, W. C.,Etnier, D. A. (1986)"Drainage evolution and fish biogeography of the Tennessee and Cumberland rivers drainage realm" In Hocutt, C.H.;Wiley, E.O. (Ed.). The zoogeography of North American freshwater fishes. (pp. 325-361) New York, New York, USA: Wiley.

The Nature Conservancy, Ozarks Ecoregional Assessment Team (2003) "Ozarks Ecoregional Conservation Assessment". Minneapolis, MN. The Nature Conservancy Midwestern Resource Office.

The Nature Conservancy World Wildlife Fund
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