282 resultados para avian species richness


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We studied the succession of small mammal species after fire in the cerrado (Neotropical savanna) of Central Brazil. Populations of small mammals were sampled with live-trapping techniques in a series of nine sites of different successional age, ranging from 1 to 26 years after fire. Ten species of small mammals were captured through all the seral stages of succession. Species richness ranged from two to seven species by seral stage. The species were arranged in different groups with respect to abundance along the succession: the first was composed of early successional species that peaked <2 years after fire (Calomys callosus, C. tener, Thalpomys cerradensis, Mus musculus, Thylamys velutinus); the second occurred or peaked 2-3 years after fire (Necromys lasiurus, Gracilinanus sp., Oryzomys scoth). Gracilinanus agilis peaked in the last seral stage. Species richness of small mammals showed an abrupt decrease from an average of four species immediately after fire to two species 5-26 years after the last fire. We propose a simple graphical model to explain the pattern of species richness of small mammals after fire in the cerrado. This model assumes that the occurrence of species of small mammals is determined by habitat selection behavior by each species along a habitat gradient. The habitat gradient is defined as the ratio of cover of herbaceous to woody vegetation. The replacement of species results from a trade-off in habitat requirements for the two habitat variables.

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The crustacean species composition in the intertidal zones of 13 sheltered unconsolidated marine beaches in south-eastern Brazil is described. Fifty-three crustacean species were collected, adding 46 species to the total reported by previous studies in the same region. Decapods dominated the community, in contrast to exposed sandy beaches where peracarids normally predominate. The species were distributed irregularly among the beaches. Richness varied markedly among sites, and was positively related to a combination of factors such as fine sand grains, high organic matter content, and relatively low silt-clay content. The presence of rock fragments enabled both rocky shore and sandy beach crustaceans to occur oil the same beaches. Richness and abundance of crustaceans showed no clear relationship to sediment grain size and slope, in contrast to the norm for exposed sandy beaches. The dominance of the tanaid Kalliapseudes schubarti in sonic areas may be a result of organic matter pollution in the region. These beaches showed higher species richness than typical sheltered and exposed sandy beaches, indicating that this sheltered, highly heterogeneous seascape is an important area for conservation.

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

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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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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The ichthyofauna of 24 stretches of streams, all of 100 m length and of fifth or lower order and most of second and third order, were sampled along four left bank tributaries (Rio do Peixe, Rio Aguapei, Rio Sao Jose dos Dourados, lower Rio Tiete of the main channel of the Rio Parana in the state of São Paulo, southeastern Brazil. Sampling of the fish fauna at each of the six sites in the four basins incorporated a standardized fish collecting methodology and a standardized documentation of environmental data serving as the basis for a comparative analysis of the collecting locations. The 8,189 fish specimens collected represented six orders, 18 families, 42 genera, and 56 species, with a total biomass of 28.8 kg. Approximately 52% of the collected species were characiforms, 28% siluriforms, 9% gymnotiforms, 5% cyprinodontiforms, 4% perciforms, and 2% synbranchiforms. The most abundant of the species were the characiforms Astyanax altiparanae (15% of total) and Knodus moenkhausii (12% of total). The two species with the largest overall biomasses were A. altiparanae (34% of total biomass) and the siluriform Hypostomus sp. (8% of total biomass). Analysis of the trophic structure of the studied ichthyofauna indicated that the 10 numerically dominant species across the 24 sampled streams can be grouped into five guilds that are in decreasing order of numerical importance: omnivores, insectivores, insectivores/invertivores, periphytivores, and algivores. Species richness in the sampled stream stretches varied from six to 20 species with an average richness of 14. The species richness estimated by extrapolation for all 24 sampled stream stretches was 67 species. The Characidae are predominant among the collected specimens with approximately 50% of both individuals and biomass, a fact hypothesized to be a function of several attributes typical of the family. Six of the 56 collected species were new to science and six other species are of indefinite taxonomic status and require further analysis in order to determine their identity.

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

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