Abstract

Orestiasis an endemic fish genus of lacustrine and lotic systems distributed on the Andes highland region (Altiplano) of Peru, Bolivia and Chile (9 degrees S to 22 degrees S). Based on morphological characters, taxonomic studies have recognized seven species on the Chilean western southern Altiplano region (17 degrees S - 22 degrees S). The current geographical distribution ofOrestiaswould be associated with historical vicariant events and fluctuations in water levels since the Pleistocene. In this context, this group arises as an interesting model to assessOrestiasmorphological adaptations in Altiplano systems. Morphological and meristic analyses were performed on ten populations ofOrestiasin the southern Altiplano. The results showed significant differences among populations. The meristic and morphometric characters were related to physical and chemical properties of their habitat. We considered the systematic validation of theOrestiasspecies and the possible future determination of new species of the populations ofO. cf.agassiiof Huasco saltpan, Isluga River and Chuviri wetland, which should be tested with trophic, genetic and karyotype analyses.