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Ecoregion Description


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Species Richness


# of Endemic Species


Threats

127: Bonneville

Major Habitat Type:

xeric freshwaters and endorheic (closed) basins

Countries:

United States

Boundaries:

This ecoregion corresponds to the Bonneville Basin, the single largest interior drainage in the Great Basin (Minckley et al. 1986). The ecoregion occupies much of western Utah with extensions into eastern Nevada, southeastern Idaho and a small portion of southwestern Wyoming. The Butte Mountains and Pequop Mountains constitute the western boundary of this ecoregion, while in Utah the eastern boundary lies to the west of the Wasatch Plateau and north of Dixie National Forest.

Drainages flowing into:

The Bonneville Basin is a closed drainage system that does not flow outward into any rivers or oceans.

Main rivers or other water bodies:

The Sevier and Bear constitute the two largest rivers in the ecoregion. Major lakes include the Great Salt Lake, Bear Lake, Utah Lake, and SevierLake, though the Great Salt Lake cannot be considered a true “freshwater” habitat due to its prohibitive salinity.

Topography:

This ecoregion forms part of the Great Basin, which is comprised of isolated north-south trending mountain ranges and valleys known as the Basin and Ridge Province. Elevation ranges from 4,000 to 8,000 ft (1,200 to 2,400 m) (McNab and Avers 1994).

Climate:

This ecoregion includes temperate steppe and continental climates (Köppen 1936). It is notably dry throughout the year, with precipitation averaging 100 – 250 mm and temperatures averaging between 7 – 13 °C (McNab and Avers 1994).

Freshwater habitats:

The Bonneville Basin was formerly Lake Bonneville, a large freshwater sea during the Pleistocene. Today Great Salt, Utah, and Sevier lakes are desert remnants of the former Lake Bonneville. The Great Salt Lake is the largest of these, with salinity levels that do not support fish, except near inflows of tributaries. Sevier Lake is ephemeral and when filled also is highly saline. The waters of Utah Lake, however, are relatively fresh and support fish species (Minckley et al. 1986).

Terrestrial Habitats:

Most of the ecoregion is comprised of shrub steppe, with dominant species including distinctly cold-temperate sagebrushes (Artemisia), saltbrushes (Atriplex), and winterfat (Ceratoides lanata) (Turner 1994). Coniferous forests are the dominant vegetation at the eastern edge of the ecoregion. 

Fish Fauna:

This ecoregion has low richness, although relatively high endemism with nearly a third of its fauna endemic to the basin.

Description of endemic fishes:

Much of the Bonneville’s distinctive biodiversity is harbored in its lakes. Bear Lake, located high in the mountains near the border of Utah, Idaho, and Wyoming, has four endemic fish species, all remnants of the Pleistocene-era Lake Bonneville fauna—the Bear Lake sculpin (Cottus extensus), Bear Lake whitefish (Prosopium abyssicola), Bonneville whitefish (P. spilonotus), and Bonneville cisco (P. gemmiferum). Utah Lake, located southeast of the Great Salt Lake and distinguished as the largest freshwater lake west of the Mississippi, historically supported two endemic fish, also Lake Bonneville remnants. These are the June sucker (Chasmistes liorus), found also in the lake’s tributaries, and the now-extinct Utah Lake sculpin (Cottus echinatus). The Bonneville Basin shares the leatherside chub (Gila copei) and the Utah sucker (Catostomus ardens) with the Upper Snake ecoregion [122], but the species can be considered endemic to both ecoregions. Finally, the Bonneville is home to two subspecies of speckled dace (Rhinichthys osculus adobe and R. o. carringtoni), as well as the endemic least chub (Iotichthys phlegethontis), historically found in the Great Salt Lake marshes and in streams along the Wasatch Front (Minckley et al. 1986; Sigler & Sigler 1994). 

Other noteworthy aquatic biotic elements:

Only two species of mussel and one species of crayfish, Pacifastacusgambelii, are native to this ecoregion, and neither is endemic (Johnson 1986).

Evolutionary phenomena:

The Bonneville ecoregion is noted for its higher taxonomic endemism (Abell et al. 2000); it contains one endemic fish genus (Iotichthys). In addition, the diversity of freshwater habitats and roughly 100 internally drained basins has resulted in high beta-diversity among water bodies.

Justification for delineation:

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

References/sources:

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

Johnson, J. E. (1986). "Inventory of Utah crayfish with notes on current distribution" Great Basin Naturalist 46 625-631.

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.

Minckley, W. L., Hendrickson, D. A., et al. (1986)"Geography of western North American freshwater fishes: Description and relationships to intracontinental tectonism" In Hocutt, C.H.;Wiley, E.O. (Ed.). The zoogeography of North American freshwater fishes. New York: John Wiley.

Sigler, J. W.,Sigler, W. F. (1994)"Fishes of the Great Basin and Colorado Plateau: Past and present forms" In Harper, K.T.;St. Clair, L.L.;Thornes, K.H.;Hess, W.M. (Ed.). Natural history of the Colorado Plateau and Great Basin. Niwot: University of Colorado Press.

Turner, J.T. (1994)"Great Basin Desertscrub" In Brown, D.E. (Ed.). Biotic communities in southwestern United States and northwestern Mexico. (pp. 145-155) Salt Lake City, UT: Univerisity of Utah Press.

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