Boundaries

This ecoregion encompasses the high-altitude plain (Altiplano) in the Puna region with associated lakes and tributaries in Peru, Bolivia and Chile. It includes the entire endorheic basins of Lake Titicaca, Lake Poopó, Salar de Coipasa, and Salar de Uyuni.

Topography

This intermontane ecoregion is nestled among the high Andean Mountains of Peru, Bolivia, and Chile, with elevations that range from 3300 to over 6100 m asl. Lake Titicaca lies at 3800 m asl within the Altiplano, a high elevation plateau that extends nearly 300 km in width. It is surrounded by the Cordillera Occidental to the west, and the Cordillera Central and Cordillera Oriental to the east. The eastern range is further divided among mountain chains like the Cordillera Apolobamba and Cordillera Real. The Cordillera Occidental to the west of the Altiplano falls within the Central Volcanic Zone lined by volcanoes such as Nevado Sajama, Parinacota, Pomerape, and the Nevados de Quimsachata (comprised of Acotango, Cerro Capurata, and Humarata). Although volcanism and glaciation formed many of the lakes within the Andes, tectonic uplift is responsible for the formation of Lake Titicaca and salt lakes of the Altiplano.

Freshwater habitats

With a surface area of 8135 km², Lake Titicaca is the largest lake in South America, and one of the highest navigable lakes in the world. It is a permanent freshwater lake with marshes and emergent vegetation like “totora” (Schoenoplectus tatora). Most of the water input comes from glacial melt water and rainfall from the cordilleras Occidental and Oriental via rivers and streams such as the Río Suches. The maximum depth exceeds 280 m, but averages around 135 m. The pH is 8.6, electrical conductivity between 1348-1521 μs/cm, and suspended matter <5 mg/l (Junk 2007). The lake experiences free circulation during the dry season from July to September. Although 90% of the water input is balanced through evapotranspiration, 10% flows out of Lake Huiñaymarca through the Río Desaguadero to the shallow, saline Lake Poopó (3700 m asl).

The Altiplano is a large endorheic basin comprised of both fresh and saline lakes, as well as salt flats. Water levels vary considerably due to pronounced seasonality in rainfall and snow melt. The salt flats, or salares, are remnants of extensive paleolakes. Salares include Coipasa, Uyuni, Chalviri, Atacama, and Arizaro. The largest of these is the Salar de Uyuni, which extends more than 10,500 km². Its salt crust covers a brine lake comprised of table salt (NaCl), lithium chloride (LiCl), and magnesium chloride (MgCl₂).

Wetland complexes, or bofedales, occur in the Altiplano above 4000 m asl. They range from permanently to seasonally humid, and can be alkaline or acidic. Common species include Distichia muscoides, Oxychloe andina, Patosia clandestine, and Plantago rigida. They regulate water flow by retaining water during the wet season and releasing it during the dry season.

Terrestrial habitats

This basin is dominated by two vegetation types: wet puna in the northern third of the ecoregion and dry puna in the southern two-thirds. Wet puna is characterized by grasses and shrubs in well-drained areas and sedges and rushes in poorly drained areas. Common trees include Buddleja coriacea and Polylepis spp. The queen of the Andes (Puya raimondii), a giant rosette endemic to the ecoregion, is the world’s largest bromeliad. This primitive genus is also the only representative of Bromeliaceae in the Andes.

Dry puna is distinguished from wet puna by its lack of annual rainfall (less than 400 mm of mean annual precipitation). Vegetation varies from shrubland steppe to grassy steppe. Some common shrubs include Baccharis incarum, B. boliviensis, Parastrephila lepidophylla, and Fabiana densa. The ecoregion also contains species of Polylepis (P. tomentella, P. tarapacana, Rosaceae, Sanguisorbeae), a tree genus found in the high Andes.

Halophytic species found around salt flats include species like Atriplex atacamensis, Distichlis humilis, Muhlenbergia fastigiata, and Parastrephia lucida.

Description of endemic fishes

These high elevation lakes and streams are not particularly rich in species; however, endemism is exceptionally high (more than 90%). In addition to the 34 endemic Orestine fishes, there is also one endemic species of Astroblepus (A. stuebeli) and two endemic species of Trichomycterus (T. laucaensis and T. chungaraensis ).

Other noteworthy fishes

Telmatobius gigas is a critically endangered frog found in high-elevation streams in puna grasslands (Stuart et al. 2008). This high altitude ecoregion is also home to migratory shorebirds and Andean waterbirds like the endemic Titicaca grebe (Rollandia microptera) and horned coot (Fulica cornuta), and several species of flamingo – James (Phoenicopterus jamesi), Andean (P. andinus), and Chilean flamingo (P. chilensis). 

Justification for delineation

This ecoregion contains a unique assemblage of highly endemic fauna. It is also one of South America’s ichthyographic provinces defined by Ringuelet (1975).

Level of taxonomic exploration

Good