Chironomid (Insecta: Diptera) assemblages along an Andean altitudinal gradient

ERIKA SCHEIBLER; ROIG JUÑENT, S.; CLAPS, CRISTINA

AQUATIC BIOLOGY

INTER-RESEARCH

Lugar: Oldendorf/Luhe; Año: 2014 vol. 20 p. 169 - 184

1864-7790

ABSTRACT: Chironomidae are an abundant, diverse and ecologically important group commonin mountain streams worldwide, but their patterns of distribution have been poorly described forthe Andes region in western-central Argentina. Here we examine chironomid assemblages alongan altitudinal gradient in the Mendoza River basin to study how spatial and seasonal variationsaffect the abundance patterns of genera across a gradient of elevation, assess the effects of environmental variables on the chironomid community and to describe its diversity using rarefactionand Shannon?s indices. Three replicate samples and physicochemical parameters were measuredseasonally at 11 sites in 2000 and 2001. Twelve genera of chironomid larvae were identified, which belonged to 5 subfamilies. Chironomid composition changed from the headwaters to the outlet and was associated with changes in altitude, water temperature, substrate size and conductivity. We found a pronounced seasonal and spatial variation in the macroinvertebrate community and in physicochemical parameters. Environmental conditions such as elevated conductivity levels and increased river discharge occurring during the summer produced low chironomid density values at the sampling sites. The rarefaction index revealed that the sampling sites with highest richness were LU (middle section of the river) and PO (lower section). However, Shannon?s diversity index indicated that LU had the lowest diversity as a consequence of the dominance of Cricotopus over the other genera found. We attribute the low diversity found in our aquatic system to the aridity of the sampling area, as has been demonstrated in studies of other similar lotic systems in this mountain region.