RESUMO
The accumulation of scientific knowledge is far outstripped by the rate of environmental disturbance from human activities in aquatic habitats. This highlights the need to develop effective proxy measures of aquatic biodiversity that can demonstrate changes in communities associated with human activities. We evaluated whether the relative abundance and species richness of Anisoptera and Zygoptera can be used as a tool to measure environmental impacts on Amazonian streams. Adult of Anisoptera and Zygoptera were sampled in 50 Amazonian streams, in the municipality of Paragominas (Pará state), Brazil, using an entomological handnet. The physical features of each stream were evaluated using an index of environmental integrity (HII). We collected a total of 1769 Odonata specimens, representing 97 species (56 were Zygoptera and 41 were Anisoptera). Habitat modification resulted in an inversion in the proportional abundance and species richness of Anisoptera and Zygoptera, where Zygoptera diversity decreased with the loss of habitat integrity, whereas Anisoptera diversity increased with habitat disturbance. A decline of 0.1 in the habitat integrity index score resulted in an increase of approximately 13 individuals and 11 species of Anisoptera, with the exact opposite effect observed for the Zygoptera. In summary, the Odonata proved to be a useful model for the assessment of Amazonian streams, with sites where more than 54% of the Odonata species were Zygoptera being classified as preserved, and those dominated by Anisoptera species (> 59%) being considered degraded. This approach has clear applications for environmental impact assessments, as it reduces the influence of sampling effort and collector experience on assessment outcomes, and does not rely upon specialist knowledge, given that members of the two suborders are easily distinguished from one and other in the field.
Assuntos
Biodiversidade , Ecossistema , Odonatos/classificação , Rios , Animais , BrasilRESUMO
Odonata have been widely used as indicators for the biomonitoring of terrestrial and aquatic habitats due to their sensitivity to environmental impacts. We aimed to determine whether the larval or adult phases of these insects were the best predictors of variation in habitat parameters and the loss of environmental integrity. Specimens were collected during three seasons (dry, rainy, and ebb) from 12 points in the Suiá-missu River basin, at the headwaters of the Xingu River in Mato Grosso, Brazil. The Protest analysis indicated a high degree of congruence between the assemblages of larvae and adults in streams with varying degrees of habitat integrity (R = 0.832, p < 0.001, m 2 = 0.307). When the congruence with environmental factors was analyzed, a significant association was found only for the larval phase (R = 0.318, p = 0.03, m 2 = 0.888). When the suborders were analyzed separately, congruence was confirmed for anisopteran adults (R = 0.338, p = 0.031, m 2 = 0.885) and larvae (R = 0.417, p = 0.003, m 2 = 0.826) and for the zygopteran adults (R = 0.345, p = 0.027, m 2 = 0.881) and larvae (R = 0.405, p = 0.011, m 2 = 0.836). These results indicate that both larvae and adults respond systematically to environmental impacts. We suggest that either life phase can be used for biomonitoring, given their effectiveness for the interpretation of disturbance in terrestrial and aquatic habitats. These findings further reinforce the effectiveness of this insect order for the detection of modifications to the environment, showing that they are good indicators of environmental conditions.