961 resultados para Brazilian sociology


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Even though shark-cetacean interactions have been the subject of numerous studies worldwide, several ecological aspects such as competition, predation risk and co-evolution remain unclear. on February 16th, 2008, during a photo-identification survey to investigate population parameters of Guiana dolphins, Sotalia guianensis, in estuarine waters of Parana State (25[degree]S; 48[degree]W), Brazil, an adult dolphin was photographed without its dorsal fin. A detailed analysis of the healed area on the injured dolphin showed that the circular, crescent-shaped outlined wound was provoked by the bite of a bull shark, Carcharhinus leucas. Wound shape, prey-predator distributional patterns (sympatry) and feeding habits of the shark species here considered were indicative of the species' identity. The wound is likely to be the result of a failed predation attempt. Interactions between C. leucas and S. guianensis should be expected, since they are sympatric along almost all of their distribution range in the tropical and subtropical western South Atlantic. The presented observation adds S. guianensis to the list of cetacean species involved in interactions with large coastal predatory sharks.

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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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In tropical forests, rodents exert a prominent role as post-dispersal seed predators, while other vertebrates apparently have a minor effect on seed predation. In some forest fragments in southeast Brazil, however, the density of rodents is unusually low, whereas terrestrial granivorous birds are abundant. In this study, we used seeds of a second-growth tree (Croton priscus, Euphorbiaceae) to investigate experimentally the relative importance of rodents and birds as seed predators in a forest fragment. We also estimated the density of terrestrial granivorous birds and trapped small mammals. Results indicate that, as a consequence of decreased rodent population and increased bird abundance, the latter are at least as important as the former as the main post-dispersal seed predators of C priscus. We interpret such apparent imbalance in the interaction between C priscus and their seed predators as a possible consequence of forest fragmentation.

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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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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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Extrafloral nectaries are nectar-secreting structures that are especially common among the woody flora of the Brazilian cerrado, a savanna-like vegetation. In this study, we provide morphological and anatomical descriptions of extrafloral nectaries (EFNs) occurring on vegetative and reproductive organs of several plant species from the cerrado, and discuss their function and ecological relevance. We describe the morphology and anatomy of EFNs of 40 species belonging to 15 woody families using scanning electron microscopy and light microscopy. We categorise EFNs following a structural-topographical classification, and characterise the vascularised and complex nectaries, amorphous nectaries and secretory trichomes. Fabaceae, Bignoniaceae, Malpighiaceae and Vochysiaceae were the plant families with the majority of species having EFNs. Ten species possess more than one morphotype of gland structure. Observations and experimental field studies in the cerrado support the anti-herbivore role of EFN-gathering ants in this habitat. Additional morphological studies of EFNs-bearing plants, including other growth forms (e.g. herbs and lianas), are being undertaken and will hopefully cast further light on the ecological relevance of these glands in the cerrado, especially with respect to their attractiveness to multiple visitors.

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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)