57 resultados para Low diversity

em Repositório Institucional UNESP - Universidade Estadual Paulista "Julio de Mesquita Filho"


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A large number of newly published and unpublished hectare plots in Amazonia and the Guiana Shield area allow an analysis of family composition and testing of hypotheses concerning alpha-diversity in the south American rain forest. Using data from 94 plots the family-level floristic patterns in wet tropical South America are described. To test diversity patterns, 268 plots are used in this large area. Contrary to a widely held belief, western Amazonian plots are not necessarily the most diverse. Several central Amazonian plots have equal or even higher tree diversity. Annual rainfall is not a good estimator for tree diversity in the Amazonia area and Guiana shield. Plots in the Guiana Shield area (and eastern Amazonia) usually have lower diversity than those in central or western Amazonia. It is argued that this is not because of low rainfall or low nutrient status of the soil but because of the small area of the relatively isolated rain forest area in eastern Amazonia and the Guiana Shield. The low diversity on nutrient-poor white sand soils in the Amazon basin is not necessarily due to their Low nutrient status but is, at least partly, caused by their small extent and fragmented nature.

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The aim of this work was to assess and compare the diversity of the ichthyofauna in three headwater rivers of Paraíba-do-Sul basin in the Serra do Mar State Park, Núcleo Santa Virgínia. A total of 1,774 specimens of 16 species of fishes belonging to 6 families were caught. Characiforms were the most abundant fish at all three sites, followed by Cyprinodontiformes, Siluriformes, and Perciformes. The Shannon index (H′), evenness (E), and the Jaccard and Morisita-Horn similarity indexes were low, indicating both low diversity and low similarity of species among the three streams. The values of these indexes should be evaluated according to the biotic and abiotic conditions in each environment. It is clear that in mountain streams of the Atlantic Forest, these low values occur because of the presence of a few abundant and many rare species.

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Savanna woody plant communities are widespread in Brazil, where this vegetation type can be divided into core-central and marginal areas within its range of distribution. The study of diversity patterns of plant communities can provide insights into the distribution, biogeography, and diversity of plant species in widespread biomes. The objectives of this study were to measure standard and phylogenetic indices of diversity in woody plant communities of the savanna vegetation of Brazil (Cerrado) throughout its extensive range. Based on a metaanalysis, the diversity indexes were compared using traditional statistical methods, a phylogenetic approach, and by mapping. Similar patterns were found for phylogenetic and traditional indexes of diversity in core and marginal areas, suggesting that both lower and higher diversity sites can occur within the Cerrado geographical area. The only difference was found in low diversity, disjunct savanna sites within the Amazon basin, which are isolated by the Amazon River from the more continuous central-southern Cerrado area.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Microstratigraphic, sedimentological, and taphonomic features of the Ferraz Shell Bed, from the Upper Permian (Kazanian-Tatarian?) Corumbatai Formation of Rio Claro Region (the Parana Basin, Brazil), indicate that the bed consists of four distinct microstratigraphic units. They include, from bottom to top, a lag concentration (Unit 1), a partly reworked storm deposit (Unit 2), a rapidly deposited sandstone unit with three thin horizons recording episodes of reworking (Unit 3), and a shell-rich horizon generated by reworking/winnowing that was subsequently buried by storm-induced obrution deposit (Unit 4). The bioclasts of the Ferraz Shell Bed represent exclusively bivalve mollusks. Pinzonella illusa and Terraia aequilateralis are the dominant species. Taphonomic analysis indicates that mollusks are heavily time-averaged (except for some parts of Unit 3). Moreover, different species are time-averaged to a different degree (disharmonious time-averaging). The units differ statistically from one another in their taxonomic and ecological composition, in their taphonomic pattern, and in the size-frequency distributions of the two most common species. Other Permian shell beds of the Parana Basin are similar to the Ferraz Shell Bed in their faunal composition (they typically contain similar sets of 5 to 10 bivalve species) and in their taphonomic, sedimentologic, and microstratigraphic characteristics. However, rare shell beds that include 2-3 species only and are dominated by articulated shells preserved in life position also occur. Diversity levels in the Permian benthic associations of the Parana Basin were very low, with the point diversity of 2-3 species and with the within-habitat and basin-wide (alpha and gamma) diversities of 10 species, at most. The Parana Basin benthic communities may have thus been analogous to low-diversity bivalve-dominated associations of the present-day Baltic Sea. The 'Ferraz-type' shell beds of the Parana Basin represent genetically complex and highly heterogeneous sources of paleontological data. They are cumulative records of spectra of benthic ecosystems time-averaged over long periods of time (10(2)-10(4) years judging from actualistic research). Detailed biostratinomic reconstructions of shell beds can not only offer useful insights into their depositional histories, but may also allow paleoecologists to optimize their sampling designs, and consequently, refine paleoecological and paleoenvironmental interpretations.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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O objetivo deste trabalho foi comparar diferentes técnicas multivariadas na caracterização de 35 genótipos de gergelim mediante 769 marcadores RAPD. As distâncias genéticas foram obtidas pelo complemento aritmético do coeficiente de Jaccard e agrupadas pelos métodos hierárquicos do vizinho mais próximo, do vizinho mais distante, das médias aritméticas não ponderadas (UPGMA), do método de otimização de Tocher e análises de coordenadas principais. O agrupamento dos genótipos foi alterado em função dos diferentes métodos usados. Adotando-se a mesma distância genética (0,36) como valor de corte, diferenciaram-se quatro grupos no método do vizinho mais próximo, 13 para o vizinho mais distante, 11 no UPGMA e quatro no Tocher. Entre os métodos hierárquicos, o UPGMA apresentou o melhor ajuste das distâncias originais e estimadas (CCC = 0,89). As análises das coordenadas principais confirmaram a baixa diversidade existente entre os genótipos. A maior divergência ocorreu entre as cultivares Seridó 1 e Arawaca 4, e a menor, entre os genótipos VCR-101 e GP-3314. As três primeiras coordenadas principais contabilizaram 35,13% do total da variabilidade, e 18 autovalores foram necessários para explicar 81% da variação genética. Os métodos UPGMA, de otimização de Tocher, e as análises de coordenadas principais são complementares na formação dos grupos.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Brazil's Atlantic Forest ecosystem has been greatly affected by land use changes, with only 11.26% of its original vegetation cover remaining. Currently, Atlantic Forest restoration is receiving increasing attention because of its potential for carbon sequestration and the important role of soil carbon in the global carbon balance. Soil organic matter is also essential for physical, chemical and biological components of soil fertility and forest sustainability. This study evaluated the potential for soil recovery in contrasting restoration models using indigenous Atlantic Forest tree species ten years after their establishment. The study site is located in Botucatu municipality, São Paulo State-Brazil, in a loamy dystrophic Red-Yellow Argisol site (Typic Hapludult). Four treatments were compared: i) Control (Spontaneous Restoration); ii) Low Diversity (five fast-growing tree species established by direct seeding); iii) High Diversity (mixed plantings of 41 species established with seedlings) and; iv) Native Forest (well conserved neighboring forest fragment). The following soil properties were evaluated: (1) physical-texture, density and porosity; (2) chemical-C, N, P, S, K, Ca, Mg, Al and pH; (3) biological-microbial biomass. Litter nutrient concentrations (P, S, K, Ca and Mg) and C and N litter stocks were determined. Within ten years the litter C and N stocks of the Low Diversity treatment area were higher than Control and similar to those in both the High Diversity treatment and the Native Forest. Soil C stocks increased through time for both models and in the Control plots, but remained highest in the Native Forest. The methods of restoration were shown to have different effects on soil dynamics, mainly on chemical properties. These results show that, at least in the short-term, changes in soil properties are more rapid in a less complex system like the Low Diversity model than in the a High Species Diversity model. For both mixed plantation systems, carbon soil cycling can be reestablished, resulting in increases in carbon stocks in both soil and litter.

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The Brazilian reservoirs have been under great anthropogenic pressure due to continued population growth, which in turn places great pressures on the environment. Given this issue, this study aimed to analyze the influence of land use on the quality and genotoxicity of water in the Itupararanga reservoir, São Paulo, Brazil. Water and sediment samples were analyzed for their quality, genotoxicity and benthic diversity, as well as their interrelationship with the landscape. The reservoir was found to be eutrophic in most sampling stations, and genetic al terations were found in radicular cells of exposed Allium cepa in some sampling stations, besides a low diversity of benthic organisms. Among the variables that most contributed to the genetic alterations and water quality are the presence of riparian vegetation, the bare soil and urban occupation. With the results obtained in this study it was concluded that the quality of water and sediment at the Itupararanga reservoir is compromised, requiring emergency managements to ensure the sustainability of water resources.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Pós-graduação em Genética - IBILCE

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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)