Chironomid assemblages in high altitude streams of the Andean region of Peru

Abstract

The diversity of genera and species of the family Chironomidae in the Andean region, as well as their variation with season and altitude, are scarcely known. Here, a semi-quantitative sampling was conducted at 35 stations with little or no human disturbance in the basin of the Canete River (Peru), situated on the western slope of the Andes, between 2553 and 4396 m a.s.l. during the dry (2004) and rainy (2005) season. A total of 38 genera of Chironomidae were found, of which 21 belong to the subfamily Orthocladiinae. No significant differences in richness of genera were found among the four different altitudinal ranges surveyed. A greater richness of genera was found during the rainy season. Most of the genera were distributed across the entire altitudinal gradient studied, especially species of the genus Cricotopus. Only Podonomopsis and Limnophyes showed evident preference for altitude range 4 (4000-4500m a.s.l.), Podonomus for altitude range 3 (3500-4000m a.s.l.), and Rheotanytarsus for altitude range 1 (2500-3000 m a.s.l.). The presence of many undetermined genera, especially Orthocladiinae, as well as the estimates indicated by the species accumulation curves, suggest that the real diversity of genera of Chironomidae in the Andean region is still far from being known.