41 resultados para environmental heterogeneity
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The mites of three rubber tree cultures (Cedral, Pindorama and Taquaritinga) in order to determine the abundance of populations, the richness, the diversity and the degree of similarity among the communities was studied. Twenty one species were found, five of which were common to the three cultures. The richness and the abundance were greatest at the beginning of the dry season. The composition of communities differed probably as consequence of the kind of neighboring vegetation to each area, and because of the acaricid pulverization on the culture of Taquaritinga, reductng the richness of mite species in that area. The influence of neighboring vegetation can be shown by the occurrence of Iphiseiodes zuluagui Denmark & Muma, 1972, a common species to citrus trees, on neighboring rubber trees in Taquaritinga, and Tenuipalpus heveae Baker, 1945, a common species on rubber trees, on a coffee culture neighbor to the rubber trees of Pindorama. This data suggests that mites move among neighbor cultures, and can be an importam factor towards pest management and control. The diversity was small on the three cultures, as a result of the occurrence of one dominam species on each area, Calacarus heveae Feres, 1992 or T. heveae, which are considered pests of the rubber tree. The small diversity and the occurrence of dominant species are patterns expected in monocultures, systems with small environmental heterogeneity.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Pós-graduação em Biologia Animal - IBILCE
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Pós-graduação em Biologia Animal - IBILCE
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Pós-graduação em Ciências Biológicas (Biologia Vegetal) - IBRC
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Pós-graduação em Biologia Animal - IBILCE
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Pós-graduação em Ciências Biológicas (Biologia Vegetal) - IBRC
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Pós-graduação em Ciências Biológicas (Biologia Vegetal) - IBRC
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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Beta diversity, the spatial or temporal variability of species composition, is a key concept in community ecology. However, our ability to predict the relative importance of the main drivers of beta diversity (e. g., environmental heterogeneity, dispersal limitation, and environmental productivity) remains limited. Using a comprehensive data set on stream invertebrate assemblages across the continental United States, we found a hump-shaped relationship between beta diversity and within-ecoregion nutrient concentrations. Within-ecoregion compositional dissimilarity matrices were mainly related to environmental distances in most of the 30 ecoregions analyzed, suggesting a stronger role for species-sorting than for spatial processes. The strength of these relationships varied considerably among ecoregions, but they were unrelated to within-ecoregion environmental heterogeneity or spatial extent. Instead, we detected a negative correlation between the strength of species sorting and nutrient concentrations. We suggest that eutrophication is a major mechanism disassembling invertebrate assemblages in streams at a continental scale.