63 resultados para habitat and ecology
em Repositório Institucional UNESP - Universidade Estadual Paulista "Julio de Mesquita Filho"
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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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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We determined microhabitat and diet niche for tadpoles from two ponds in an agricultural landscape. Additionally, we verified the intraspecific variation in resource use, and if diet and microhabitat use were correlated. Tadpoles found in the two ponds differed in microhabitat use, because in the larger pond they explored deeper places far from the margin. There were three groups with high microhabitat niche overlap. In both ponds, plant cover was the best descriptor to explain interspecific variation in microhabitat use. Tadpoles of all species ingested mainly Bacillariophyceae and Trachellomonas however the diet differed intraspecifically in the species from the two ponds. Ten items in the temporary pond and 15 items in the permanent one were ingested by all species; however, the relative abundance of each item differed. Diet similarity was not correlated to similarity in microhabitat use. In this study, diet was as important as microhabitat use to explain resource partitioning.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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The Brazilian species of Paspalum L. (Poaceae) groups Virgata and Quadrifaria are revised based on herbarium material and live specimens of recent collections. The Virgata taxa are P. wettsteinii, P. rufum, P. regnellii, P. conspersum, P. virgatum and P. commune, while Quadrifaria encompasses P. intermedium, P. densum, P. millegrana, P. durifolium, P. brunneum, P. usteri, P. plenum, P. quadrifarium, P. coryphaeum, P. exaltatum and P. haummmanii. Both groups are commonly found throughout the country, but rare in the wet areas of the Amazonian forest, and better characterized as megatherm plants.
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The effects of habitat complexity, induced by construction of artificial reefs, on the fish assemblages in the Barra Bonita reservoir, Brazil, and in the lotic zone immediately below the dam were studied. Four artificial reefs were constructed in each habitat at variable distances from the shore. Multiple correspondence analysis showed that the factors distance from the shore and type of habitat were determinants for the group formation, and artificial reefs had a lesser effect. Fish species composition was about the same at locations with and without reefs.
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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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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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A common approach used to estimate landscape resistance involves comparing correlations of ecological and genetic distances calculated among individuals of a species. However, the location of sampled individuals may contain some degree of spatial uncertainty due to the natural variation of animals moving through their home range or measurement error in plant or animal locations. In this study, we evaluate the ways that spatial uncertainty, landscape characteristics, and genetic stochasticity interact to influence the strength and variability of conclusions about landscape-genetics relationships. We used a neutral landscape model to generate 45 landscapes composed of habitat and non-habitat, varying in percent habitat, aggregation, and structural connectivity (patch cohesion). We created true and alternate locations for 500 individuals, calculated ecological distances (least-cost paths), and simulated genetic distances among individuals. We compared correlations between ecological distances for true and alternate locations. We then simulated genotypes at 15 neutral loci and investigated whether the same influences could be detected in simple Mantel tests and while controlling for the effects of isolation-by distance using the partial Mantel test. Spatial uncertainty interacted with the percentage of habitat in the landscape, but led to only small reductions in correlations. Furthermore, the strongest correlations occurred with low percent habitat, high aggregation, and low to intermediate levels of cohesion. Overall genetic stochasticity was relatively low and was influenced by landscape characteristics.
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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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Habitat split is a major force behind the worldwide decline of amphibian populations, causing community change in richness and species composition. In fragmented landscapes, natural remnants, the terrestrial habitat of the adults, are frequently separated from streams, the aquatic habitat of the larvae. An important question is how this landscape configuration affects population levels and if it can drive species to extinction locally. Here, we put forward the first theoretical model on habitat split which is particularly concerned on how split distance - the distance between the two required habitats - affects population size and persistence in isolated fragments. Our diffusive model shows that habitat split alone is able to generate extinction thresholds. Fragments occurring between the aquatic habitat and a given critical split distance are expected to hold viable populations, while fragments located farther away are expected to be unoccupied. Species with higher reproductive success and higher diffusion rate of post-metamorphic youngs are expected to have farther critical split distances. Furthermore, the model indicates that negative effects of habitat split are poorly compensated by positive effects of fragment size. The habitat split model improves our understanding about spatially structured populations and has relevant implications for landscape design for conservation. It puts on a firm theoretical basis the relation between habitat split and the decline of amphibian populations. © 2013 Fonseca et al.