Composition and diversity of Ephemeroptera (Insecta) nymph communities in the middle section of the Jacuí River and some tributaries, southern Brazil.

The article evaluates the diversity and taxonomic composition of the nymph communities of Ephemeroptera or mayflies in the central region of Rio Grande do Sul in southern Brazil. In comparison to the estimated maximum theoretical diversity, the diversity of nymphs that was observed in the total area is high. There appears to be an association between the higher diversity of Ephemeroptera nymph assemblages and habitat complexity. A table showing the four sampling points and their physical characterization between June 2001 and May 2002 in the area is presented.