Estudos sobre estimadores de riqueza de especies, perturbações experimentais e persistencia ao longo de cinco anos em comunidades de macroinvertebrados bentonicos em riachos

AUTOR(ES)

Adriano Sanches Melo

DATA DE PUBLICAÇÃO

2002

RESUMO

In this thesis I address topics of species richness estimation and the role of disturbance in streams. In an evaluation of species richness estimators, alI methods were dependent on sample size. Such dependence is in part due to the non-stabilization of the curve of accumulation of rare species. The results indicate that estimates of species richness in an area are not reliable, although they might be useful for comparative purposes. Despite the lack of reliable methods to estimate species richness in an area, in a second evaluation work I show that several methods can be used to estimate species richness in extrapolated sample sizes. The main application of such methods would be in the standardization of different sample sizes. Two experiments were carried out to investigate the response of stream macroinvertebrate communities to experimental disturbance. In the first study, done in New Zealand, response of communities in streams draining pastures did not differ from that observed in streams draining native tussock fields. There was a decrease in abundance following the disturbance evento Eight days after the disturbance event, abundance was similar to control levels. Species richness remained unchanged. Immediately after the disturbance event there was an increase in patchiness of the stream communities. In the second experiment, stones in three streams differing in size were disturbed. I tested the hypothesis that recovery would be fastest in the medium-sized stream. The colonization patterns were similar in alI three streams, causing the rejection of the stated hypothesis. In a study of persistence of invertebrate communities inhabiting five streams during five years, it was observed that winter (dry season) samples were more concordant over years than summer (rainy season) samples. The hypothesis that community variability increases with time was tested. The hypothesis was supported, although the increase in variability was much more conspicuous for summer than for winter communities

ASSUNTO(S)

inseto diversidade biologica invertebrado ecologia

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