Fisheries of the Altiplano, dating from 1500 to 2000 BC, are active in the Andean inter-montane plateau that extends from Ancash, Perú, to Antofagasta, Chile, at altitudes above 3600 m. The ancient and remote nature of these systems has merited the inclusion of many areas as National Parks and RAMSAR sites. Among 58 native fish species, 45 belong to the killifish complex Orestias and the rest to the catfish complex Trichomycterus. The main fishery resources consist of “ispi”, Orestias ispi, with 32 175 (64.5%) metric tons and “karachi”, Orestias of the group agassii, with 455 metric tons (0.9%). The introduced fishes “silversides”, Odontesthes bonariensis, and “trouts”, Oncorhynchus mykiss, contribute 16 900 metric tons (33.9%) and 324 metric tons (0.7%) respectively. Hydro-acoustic evaluations show a permanent diminution of the endemic Orestias. Lake species such as O. pentlandii “boga” and O. cuvieri “humanto” were important for their biogeographic relationships and were highly endemic. Native fishes are nowadays threatened by the salmonids, Oncorhynchus mykiss, Salvelinus namaycush, Salvelinus fontinalis and Salmo trutta, introduced since 1939. Later, the silverside Odontesthes bonariensis was introduced during 1955–1956.

This study presents phylogenetic molecular data of the Chilean species of Orestias to propose an allopatric divergence hypothesis and phylogeographic evidence that suggests the relevance of abiotic factors in promoting population divergence in this complex. The results reveal that diversification is still ongoing, e.g. in the Ascotán salt pan, where populations of Orestias ascotanensis restricted to individual freshwater springs exhibit strong genetic differentiation, reflecting putative independent evolutionary units. Diversification of Orestias in the southern Altiplano may be linked to historical vicariant events and contemporary variation in water level; these processes may have affected the populations from the Plio-Pleistocene until the present.

This study examines the limnology and ecology of two high altitude wetlands, Lirima (19°51'24 S; 68°55'02 W; 4000 m asl) and Caya (20°37'21 S; 68°58'28 W; 3700 m asl), located in the Chilean Altiplano. Both wetlands are formed by the evaporitic remnant basins of paleolakes which occupied an extensive area of what today is known as the Altiplano. These systems have a negative hydrological balance, receiving their water from groundwater, snow melt and limited seasonal rains. An ongoing negative water balance and the sediment characteristics in the region have accelerated the salinization process in these systems, as shown by their present physicochemical characteristics. Nutrient values were typical of mesotrophic to eutrophic systems. The ionic content classifi es Lirima as a sodium sulfated wetland and Caya as a calcium chloride one. Conductivity values ranged between 778 μS/cm at Lirima to 2100 μS/cm at Caya, and were refl ected in the differences in biodiversity found in these systems. The Lirima wetland supports a population of the endemic fi sh Orestias aff. agassii found in several Evolutionary Signifi cant Units (ESU) across the region. Microbial diversity in the water column was characterized by the presence of 5 bacterial phyla and related genera (e.g. Psychrobacter, Bacillus, Eryhtobacter, Halomonas). We present information on several key ecosystem components including macrophytes, plankton, benthos, fi sh and birds. This descriptive paper highlights the unusual limnological and biological characteristics of high altitude wetlands and highlights the importance of describing their biological communities across levels of organisation (e.g. microbial through to higher vertebrates) as well as their functional role, interactions and sensitivity to changes in water availability. KEYWORDS:Altiplano, biodiversity, endemism, evolutionary signifi cant units, salinity. RESUMENEste estudio examina la limnología y ecología de dos lagos de altura, los humedales de Lirima (19°51'24 S; 68°55'02 W; 4000 m asl) y Caya (20°37'21 S; 68°58'28 W; 3700 m asl) que están ubicados en el Altiplano Chileno, representando cuencas evaporíticas remanentes de antiguos paleolagos los cuales ocuparon una amplia zona en lo que hoy conocemos como Altiplano. Estos sistemas tienen un balance hídrico negativo, recibiendo su agua desde fuentes freáticas, derretimiento de nueves y escasas lluvias estacionales. Las características del suelo junto con la demanda de agua en la región han acelerado el proceso desalinización en estos sistemas siendo refl ejado en las características químicas actuales. Los valores de nutrientes fueron típicos de sistemas mesotrófi cos a eutrófi cos. El contenido iónico clasifi ca Lirima como un humedal sodio sulfatado y el humedal de Caya como un humedal de cloruro de calcio. Los valores de conductividad fl uctuaron entre 778 μS/cm en Lirima a 2100 μS/cm en Caya, refl ejándose en las diferencias de biodiversidad encontrada en estos sistemas. El humedal de Lirima conserva el pez endémico Orestias que represe...

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