Similarity and diversity between aquatic insect populations in streams of first and second order, south of Brazil

Abstract

Aquatic communities of macroinvertebrates are influencied by rapid velocity, habitat heterogeneity and other characteristics. This study examined a relationship between aquatic insects diversity with hydrologic order of two streams. We tested following hypothesis: diversity of insects associated with the same substrate in equal parts of streams, classified in different orders, are similar. Samples of litter were collected in middle stretches of stream Cascatinha (first order) and stream João Pinheiro (second order), Tibagi river basin, Telêmaco Borba, Paraná, Brazil. Diversity of each stream was obtained by Shannon index. Diversity values were low for both streams (0.8 for the first order stream and 0.89 for the second order stream) with no statistical difference (t = -1.12; p = 0. 27). Similarity between the streams was 0.51. These results allowed us to verify that, to studied streams, hydrological order has no effect on aquatic insects diversity (F= 0.14, p= 0.71), so the hypothesis was accepted. The most abundant taxon in both streams was Chironomidae (Diptera), representing 82.7% of total collected. However when Chironomidae was removed from analysis, the hypotesis was refused. An high abundance of Chironomidae individuals had influenced values of local diversity.