Boundaries

The Valdivian Lakes ecoregion extends from the Río Toltén drainage in the north (39° S) to Isla Grande de Chiloé in the south (43° S). This ecoregion includes the lake district of southern Chile, with Lago Villarrica to the north and Lago Llanquihue to the south, plus the island of Chiloé. It is limited to east by the Western Andes.

Topography

The ecoregion lies within the South Volcanic Zone, which resulted from the subduction of the Nazca Plate under the South American Plate. The topography in this section is divided into the Coastal Zone, Central Depression, and slopes of the Western Cordillera, with elevations ranging from sea level to 3100 m asl (Hijmans et al. 2004). Volcanoes include Villarica (2847 m), Quetrupillán (2360 m), Mocho-Choshuenco (2422 m, 2415 m), Puyehue (2236 m), Puntiagudo (2493 m), Osorno (2652 m), and Calbuco (2003 m). Of these, Villarica and Osorno are the highest, both of which support small icecaps. The South Volcanic Zone is the most active area in Chile, and Villarica is one of the most active volcanoes in the entire Andean arc. In addition to composite stratovolcanoes are calderas, lava fields, and hundreds of minor eruptive centers. This area is underlain by pre-Andean basement and Mesozoic-Cenozoic igneous rocks (Moreno & Gibbons 2007).

The Central Depression or Central Valley is a low fault zone covered by volcanic ash and glacial moraines lying between the Coastal Cordillera and Western Cordillera (WWF 2001). The southernmost part of the Central Depression is submerged in the ocean and forms the Gulf of Ancud. Isla de Chiloé is an extension of the Coastal Cordillera (Moreno & Gibbons 2007).

Freshwater habitats

In this ecoregion glaciers reached their maximum extent during the Quarternary around 20-21,000 BP, and likely contributed to the glacially-deepened lakes carved out of the soft sedimentary soil of the Central Valley (Clapperton 1994). Because the Central Valley is closer to sea level in this ecoregion, rivers descending from the Andes empty into these lakes, and then drain into the ocean through other rivers, some of which are navigable (Moreno & Gibbons 2007). These monomictic, temperate lakes are generally oligotrophic with high water transparency and low productivity (Soto 2002).

Terrestrial habitats

This ecoregion is home to the Valdivian temperate forests, which is a heterogeneous mosaic of forest types influenced by a diverse topography, geology, and climate. A long history of biogeographic isolation has resulted in exceptionally high endemism (90% at the species level and 34% at the genus level for woody species), as well as monogeneric families such as Aextoxicaceae, Gomotergaceae, Desfontaineaceae, Eucryphiaceae, and Misodendraceae (WWF 2001).

Description of endemic fishes

This ecoregion falls within Dyer’s (2000) Southern area of endemism, which includes no endemic genera and three endemic species: Cheirodon australe (Characidae), Galaxias globiceps (Galaxiidae), and Diplomystes camposensis (Diplomystidae). These endemics indicate an East-West divergence caused by the uplift of the Andes.

Justification for delineation

This ecoregion encompasses the Southern area of endemism, which extends from the Río Valdivia to the Isle of Chiloé (Dyer 2000).

Level of taxonomic exploration

Fair