Congruence and the Biomonitoring of Aquatic Ecosystems: Are Odonate Larvae or Adults the Most Effective for the Evaluation of Impacts.

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.