Biological indicators of diversity in tropical streams: Congruence in the similarity of invertebrate assemblages

Abstract

Surrogate indicators are important alternatives to overcome the shortage of total biodiversity data for planning and implementing conservation measures. The most important premise of this approach is congruence among surrogate candidates and among different assemblages. The aim of this study was to evaluate abundance and incidence congruence between invertebrate assemblages at two taxonomic resolutions (genus and family), and between invertebrate assemblage (genus) and three groups of taxa (EPT, Odonata, and Trichoptera). We also evaluated the congruence between functional groups of EPT and the taxonomic groups listed above. Data were collected from 51 stream sites distributed along a disturbance gradient in the rural area of the Paragominas municipality of the state of Pará, Brazil. We used Procrustes analysis to test congruence between invertebrate assemblages at the multiple taxonomic resolutions listed previously. Family taxonomic level was a good substitute for similarity patterns measured at the genera level. EPT genus also were highly congruent with whole invertebrate assemblage (genus level) variation. Trichoptera had greater congruence with all macroinvertebrate genera than did Odonata. The congruence between EPT functional groups and groups of taxa was greater than r=0.70. In general, taxonomic and functional metrics responded similarly to environmental conditions (water quality, channel morphology, substrate, riparian vegetation cover). Trichoptera (abundance), EPT (genera and functional groups), or invertebrate families appear to be reasonable surrogates for Amazon stream invertebrate assemblage as biological indicators for assessing and conserving streams influenced by agriculture.