Efeito da complexidade estrutural e da distância da fonte de dispersão sobre a densidade e diversidade de invertebrados : um experimento com macrófitas artificiais.

Abstract

The structural complexity of habitats and distance from dispersion source has been considered important determinants of species diversity. Measures of fractal geometry are a strong alternative to quantify the first variable. In this paper we tested the hypothesis that structural complexity and distance from a dispersion source affect the density and diversity of macro-invertebrates on submerged macrophytes. To test this hypothesis we used artificial substrates with different fractal dimensions, which were incubated at different distances from a dispersion source (a stand of macrophyte) in a Neotropical aquatic environment. The relationship between structural complexity of macrophytes and density and diversity of total invertebrates attached on artificial substrates was significant. On the other hand, distance from dispersion source affected negatively both the density and diversity of the attached invertebrates. However, it was noticeable that for Oligochaete the effects of structural complexity was significant in the artificial plants positioned farer, but it was not significant in the plants positioned closer to the dispersion source. Thus, the effects of complexity depended on distance from dispersion source at least for this specific group of macro-invertebrates. These results highlight that both, structural complexity and distance from dispersion source, should be considered together to explain diversity of invertebrates in river-floodplain systems. In addition, our results also showed a great potential in using fractal dimension as a tool to quantify structural complexity in aquatic habitats, especially at small spatial scales perceived by macroinvertebrates.