Does the habitat structure control the distribution and diversity of the Odonatofauna?

The statement that the habitat complexity and structure govern the abundance and diversity of biological communities has been widely investigated. In this context, we assumed the hypothesis of habitat heterogeneity, that is, the higher habitat complexity leads to greater diversity of Odonata. In addition, we analyzed the influence of habitat structure on the distribution of this community, and evaluated the effects of abiotic variables. Odonata larvae were collected with sieves and by electrofishing in ten neotropical streams belonging to the Pirapó River basin. Forty species of Odonata were registered, which were distributed in eight families, Libellulidae stood out with the highest richness. The high gamma diversity and distribution of Odonata were associated with habitat heterogeneity in these streams. However, the abiotic variables also seem to affect the distribution of Odonata species, in view of the impact of the land use in the vicinity of streams.

Diet and feeding selectivity of a benthivorous fish in streams: responses to the effects of urbanization.

This study evaluated the diet and feeding selectivity of the catfish Imparfinis mirini in streams with different degrees of urbanization and the effect of rainfall on the availability of prey. The diet was based especially on Chironomidae and Trichoptera. Significant spatial differences in diet were found between the streams; the diet of the fish was similar in the rural and peri-urban streams, and differed from that in the urban stream. Seasonality was an unimportant factor affecting the species' diet, which did not differ significantly between the rainy and dry periods in any of the streams. Fish from the urban stream fed more according to what was available in the environment, while fish from the peri-urban and rural streams showed higher degrees of selectivity. The results indicate that environmental conditions influenced the diet and prey selection of this species in response to the differences in diversity and abundance of the food organisms. They indicate that trophic studies of benthivorous fishes, such as I. mirini, may represent an alternative way to assess human effects on streams.