Orinoco High Andes
Paulo Petry, Jennifer Hales
Major Habitat Type
Drainages flowing into
Main rivers to other water bodies
The river systems in this ecoregion include mountain drainages above 500 m elevation that drain into the Orinoco system. These include headwaters of the Guaviare, Meta, Arauca, and Apure rivers, as well as Lake Valencia. The region also includes two Andean lake drainages, Lake Tota in Colombia and Lake Valencia in Venezuela.
This ecoregion includes the eastern slopes of the Cordillera Mérida above 500 m elevation draining into the Orinoco drainage in Colombia, and the southeastern face of the Andes Cordillera Oriental draining into the Orinoco basin. The upper limit is determined by the drainage divide between the Orinoco, Magdalena, and Maracaibo basins. The eastern limit is the drainage divide between the upper Apure and Manapire drainages.
Elevations rise from roughly 500 m to more than 5000 m in the Cordillera Oriental in the Northern Andes and the Cordillera Mérida. The Sierra Nevada del Cocuy (5493 m) stands out as the highest elevation in the ecoregion. The landscape is dominate by steep terrains with deep valleys.
Lago Tota lies in the upper Cordillera Oriental at about 3000 m asl. Sistema Lacustre de Chingaza is a Ramsar site comprised of lagoons and wetlands. The upper reaches are dominated by small streams draining paramo systems. The transition zone between the upper regions and the lowlands is characterized by high gradient, fast moving streams.
The main terrestrial ecoregions include the Cordillera Oriental montane forests in the south and Venezuelan Andes montane forests in the north. Páramo occurs at the highest elevations.
Description of endemic fishes
There are only six endemic fishes currently in this ecoregion. The monotypic genus Rhizosomichthys (Trichomycteridae) is also endemic. The highly unusual trichomycterid Rhizosomichthys totae was confined to Lago Tota and is presumed to be extinct. Others include Trichomycterus venulosus and Dolichancistrus fuesslii. The Lake Valencia system contains two endemic species, Lithogenys Valencia and Pimelodella tapatapa.
Other noteworthy fishes
Astroblepus is the only genus of the family Astroblepidae. Also known as naked sucker-mouth or climbing catfishes, astrolepid catfishes are characteristic of the higher mountain ranges of the Andes. The taxonomy of Astroblepus remains problematic and additional endemic species are likely to be recognized once the taxonomy is resolved. Lake Valencia contains an assemblage of 32 species, most notably Ancistrin loricarrids of the genus Chaetostoma and Lasiancistrus.
One species of migratory catfish occurs in this ecoregion: Pseudoplatystoma orinocoense.
Justification for delineation
Because Astroblepid catfishes are distinct components of high-elevation freshwaters along the Andes forefront, this family’s distribution was critical to informing the delineation of the high Andean ecoregions. This ecoregion is also distinguished by the presence of some groups of mountain dwelling ancistrins and rivers that drain from the Andes into the Orinoco basin.
Level of taxonomic exploration
- Hijmans, R. J., S. Cameron and Parra., J. (2004) \WorldClim, Version 1.4 (release 3). A square kilometer resolution database of global terrestrial surface climate\ "<"[http://www.worldclim.org]">" (16 July 2009)
- IUCN (2009) \IUCN Red List of Threatened Species. Version 2009.1\ "<"http://www.iucnredlist.org">" (08 July 2009)
- Lasso, C. A., Lew, D., Taphorn, D., et al. (2004). "Biodiversidad ictiológica continental de Venezuela. Parte I. Lista de especies y distribución por cuencas" Memoria de la Fundación La Salle de Ciencias Naturales 159-160 pp. 105-195.
- Lowe-McConnell, R. H. (1987). "Ecological studies in tropical fish communities" Cambridge, UK: Cambridge University Press.
- Wetlands International (2002) \Ramsar Sites Database: A directory of wetlands of international importance\ "<"http://ramsar.wetlands.org/">" (2003)
- World Wildlife Fund (WWF) (2001) \Terrestrial Ecoregions of the World\ "<"http://www.worldwildlife.org/wildworld/profiles/terrestrial_nt.html">"
- Buitrago–Suárez, U.A.;Burr, B. M. (2007). "Taxonomy of the catfish genus Pseudoplatystoma Bleeker (Siluriformes: Pimelodidae) with recognition of eight species" Zootaxa 1512 pp. 1-38.