Odonata (Insecta) as a tool for the biomonitoring of environmental quality

•Different assemblage characteristics can potentially be used to assess loss of environmental integrity.•Species composition was the characteristic that best evaluated ecological integrity.•Taxonomic diversity and taxonomic distinction also achieved good results.•Species richness and abundance/biomass relationships did not provide good responses.•Deconstructing Odonata assemblages and choosing the right indicators are mandatory for efficient ecological assessments.

Despite the fundamental dependence of human populations on water resources, a range of anthropogenic impacts, in particular the removal of riparian vegetation, threaten freshwater environments. One of the most effective means of evaluating the effects of anthropogenic disturbance in aquatic ecosystems is the use of bioindicators, and the insects of the order Odonata are among the most efficient indicators, due to their enormous sensitivity to environmental changes. In this context, the present study aimed to verify which parameters of the odonate community (species richness, abundance/biomass, composition, taxonomic diversity and taxonomic/phylogenetic distinctness) are most effective for the evaluation of the loss of environmental integrity. The study focused on 50 streams in the northeast of the Brazilian state of Pará. The streams were sampled during the dry season, between June and August 2011. The physical characteristics of each stream were evaluated using a Habitat Integrity Index (HII). The species composition provided the best parameter for the evaluation of ecological integrity, providing a relatively accurate assessment at a lower mean research cost than other parameters. Taxonomic diversity and distinctness also provided relatively reliable results, contributed additional information on the evolutionary relationships among the odonate taxa, and also provided a low-cost approach. Deconstructing communities is necessary to detect impacts, considering the considerable variation in the environmental requirements of the different species. Overall, the parameter that best responded to gradients of disturbance was species composition, followed by diversity and taxonomic distinctness. Given these findings, odonate-based biomonitoring should focus on these parameters to guarantee the optimal detection and evaluation of habitat alterations.