Composition and structure of the Chironomidae (Insecta: Diptera) assemblage of Ventania hill system streams (Argentina) along an altitudinal gradient

A two-year study was conducted in a conservation area of the Ventania hill system where Pampean grassy steppes and their headwater springs maintain conditions close to natural ones. The composition structure Chironomidae (Insecta: Diptera) along two short pristine streams relationship with physicochemical variables were analyzed. total 15444 individuals belonging 37 species four subfamilies identified. An assemblage more similar those described for Andean or Argentine extra-Andean than surrounding Pampas observed. Orthocladiinae showed highest Podonominae lowest taxonomic richness density. Chironominae best represented downstream by genera wide distribution. From five reported Andean-Patagonic region, three them (Podonomus Philippi, Parochlus Enderlein Podonomopsis Brundin) collected. presence Podonomus represent reports at lower altitudes both genera. differed between seasons, only water conductivity an altitudinal gradient. Those prevailing piedmont sites correlated positively conductivity. With few exceptions, collected recorded seasons. In Toro stream, density significantly Spring second year. This provides ecological systematic baseline knowledge insect group widely used biomonitoring aquatic environments, provide biological information that supports importance preserving this area.