South-westward movements of Neotropical fishes and decline of Andean species

CUSSAC, V. E.

Madison

Simposio; 10th International Congress on the Biology of Fish; 2012

Cooling of Southern South America during the Oligocene impoverished characin and siluroid diversity in the Andean Region, south and west of the South American transition zone. Gymnocharacinus bergii (Characidae) remains isolated in a thermal stream (40ºS), Hatcheria macraei (Trichomycteridae) reaches 47ºS keeping an ULT appropriate for the Neotropics (31ºC), and a new diplomystiid has been discovered in the Baker river basin (47ºS). Ecological niches, opened after cooling, aridization, marine incursions, glaciations, and volcanism, remained occupied by temperate secondary freshwater fishes like Percichthyidae, Atherinopsidae, and Galaxiidae. In the last decades, seven Neotropical species moved southward and westward between Colorado and Negro river basins. In addition, Galaxiidae species showed extirpated localities towards the north of their distribution areas, Patagonian silverside suffered introgression by its Neotropical counterpart Odontesthes bonariensis, and Percichthys trucha is being displaced by exotic Cyprinus carpio in Colorado and Negro basins. Accordingly, exotic salmonids have also declined in northern Patagonia.