Boundaries

This ecoregion encompasses the Río Desaguadero drainage in western Argentina. It is limited to the north and east by the drainage divide between the Río Desaguadero and the Central endorheic basin along the Sierra de la Punilla and Sierra de las Quijadas; to the west by the Andes Cordillera; and to the south by the drainage divide with the Río Colorado.

Topography

The topography of this ecoregion varies widely, descending from Mt. Aconcagua (6960 m), which is the highest mountain in the Americas, down to 250 m in the semi-flat lands in the southeast (Hijmans et al. 2004). The topography is characterized by high and low mountain ranges, as well as hills, valleys, bolsones (elevated valleys), and arid plains (López et al. 2002). Other high mountains in the ecoregion include Mt. Pissis (6858 m) and Mt. Tupungato (6800 m).

Freshwater habitats

This ecoregion includes a group of streams in the Desaguadero drainage that flow through dry courses, sloughs, and lagoons, and finally into the upper Río Colorado (López et al. 2002). All of the permanent rivers originate in the Andes, have cold water and carry high loads of fine sediments.  Other noteworthy areas include a lacustrine complex called the Lagunas de Guanacache; Laguna Brava, which is a system of saline and hyper-saline lagoons; and  Laguna de Llancanelo, which is a high elevation salt lake that receives water from the Río Mendoza, Mocho, and Chacay streams, as well as subterranean waters (Wetlands International 2005). Additionally, a series of extensive inland marshes (bañados) are found throughout the ecoregion, of which Bañado del Atuel, Bañado del Guanacache, and Cienaga del Tulumaya are the largest.

Terrestrial habitats

Southern Andean steppe occurs in the Andes Cordillera, with tussock grasses and shrubs at lower elevations, low shrubs and cushion plants at intermediate elevations, and perennial forbs at higher elevations. To the east the vegetation transitions to the lower altitude and warmer Argentine Monte Desert, which is a scrubland dominated by characteristic jarillas (Larrea), as well as retamos (Bulnesia), mancapotrillos (Plectocarpa), pichanilla (Cassia aphylla), and brea (Cercidium praecox) (WWF 2001).

Description of endemic fishes

The ecoregion contains four endemic Trichomycterids, including Silvinichthys mendozensis, S. leoncitensis, Trichomycterus heterodontus, and T. riojanus. Despite being a widespread genus, Trichomycterus species in this ecoregion have generally limited ranges within two or less ecoregions. Only Trichomycterus areolatus has a wider range that extends into the South Andean Pacific Slopes [341], Patagonia [348], and Valdivian Lakes [349] ecoregions.

Other noteworthy fishes

The monotypic genus Hatcheria (H. macraei) is located in the Cuyan-Desagudero and Patagonia [348] ecoregions. Silvinichthys is found in this ecoregion as well as in the Lower Parana [345].

Justification for delineation

This ecoregion falls within the Subandean-Cuyan ichthyographic province of the Austral Subregion (Ringuelet 1975). The families Percichthyidae and Diplomystidae reach their northern limit in this ecoregion (Liotta 2005).

Level of taxonomic exploration

Good