| Popis: |
ABSTRACT Tropical streams feature high variety of habitats and environmental gradients, which reflect on the greater richness of aquatic insects. In this way, we evaluate if the diversity of aquatic insects of prey and predator categories is influenced by the type of substrates or by longitudinal portions in Cerrado streams. Our hypothesis is that prey and predator diversity will be determined by the type of substrate, assuming that the substrate serves as a source for foraging and / or refuge. In addition, the folhiço substrate will present greater abundance and richness due to the availability of shelter and food provided by this type of substrate. There will be differences in prey and predator composition among substrates, since some species have associations with the substrate type. The portions of the stream will have no effect on the diversity of prey and predator, since in streams of up to third order does not present considerable changes in physical characteristics. The study was carried out in nascent (1st order), intermediate (2nd) and estuary (3rd), in two streams, during dry and rainy periods. Five subsamples of sand, gravel, rocks or boulders were collected, backwaters, rapids and roots (substrate). The substrate influenced all prey and predator responses (abundance, richness and composition), but the environment (longitudinal portions) did not influence the abundance and predator composition. The influence of substrates on the diversity of prey and predators evidences the importance of riparian vegetation as a source of allochthonous material in bedside streams. |
