Landscape composition as a determinant of diversity and functional feeding groups of aquatic macroinvertebrates in southern South American rivers

Abstract

Changes in land use which directly or indirectly affect freshwater fauna constitute one of the principal anthropic factors which have caused world biological diversity to disappear rapidly during recent decades. This fauna includes aquatic benthic macroinvertebrates, organisms presenting temporal and spatial variation due to a variety of factors, one of which is the diverse food resources available in the rivers. To assess this, the distribution, abundance and characterisation of the functional feeding groups of aquatic macroinvertebrates were analysed, together with the physical-chemical variables in the environments of four coastal river basins of southern south-central Chile. 104 taxa of macroinvertebrates were recorded, the principal component of the community being the Diptera. The abundance and richness of taxa were more conspicuous in summer and poorer in winter. The most abundant species belong to the Orden Ephemeroptera and Plecoptera, and the most abundant sampling station was the one at the highest altitude, while the least abundant was the lowest. The functional feeding groups which were most abundant spatially and temporally were the collectors and the shredders. The physical-chemical water variables proved to be of exceptional quality in all the stations. These results suggest that policies governing changes in land use in central and southern Chile should take into account the dramatic alterations that these changes impose on the macroinvertebrate community. Policies for biodiversity conservation should therefore focus on these small but important organisms in the north Patagonian region of South America, which is a hot spot of world diversity.