Effects of urbanization on stream habitats and associated adult dragonfly and damselfly communities in central Brazilian Amazonia

Thirty streams, located in Manaus in the central part of Brazilian Amazonia, were examined to evaluate the correlations between environmental integrity and the local communities of adult dragonflies and damselflies. The presence of damselflies would have a positive correlation with environmental integrity, and dragonflies a negative one due to their contrasting ecophysiological requirements. The environmental integrity of each site was estimated based on the Habitat integrity index (HII), which was modified for this study in an urban area. The hypothesis that would be differences in assemblage composition between streams in differently urbanized areas was supported, possibly because most damselfly species are considered to be specialists that are found in pristine habitats, whereas dragonflies seem to be generalists and are likely to be found in disturbed environments. The ordination indicated systematic differences in community composition based on the degree of conservation of the environment, with the communities found in well-preserved habitats being distinct from those found in intermediate and degraded ones. Differences in the composition of odonate communities reflect differences in the integrity of the environment, but they can also provide a measure of the intensity of impacts, thus contributing to the development of effective conservation strategies. In addition, the HII, which is applied rapidly and easily, provides environmental managers with an objective measure of the degree of alteration of aquatic habitats. Maintenance of forest cover along watercourses is clearly essential for the conservation of hydrological resources and the aquatic organisms that depend on these environments.