Diversidade de comunidades de pequenos mamíferos de três fitofisonomias [sic] do Cerrado no Brasil Central : partição da diversidade regional em componentes alfa e beta

Dissertação (mestrado)—Universidade de Brasília, Instituto de Ciências Biológicas, Departamento de Ecologia, Programa de Pós-Graduação em Ecologia, 2013.A diversidade de grupos animais pode estar relacionada à heterogeneidade e/ou à complexidade do ambiente. No domínio vegetacional Cerrado, a alta diversidade de pequenos mamíferos tem sido atribuída à heterogeneidade ambiental e a influência da complexidade ainda é uma questão aberta. O objetivo deste trabalho foi avaliar a partição da diversidade de pequenos mamíferos de uma região de Cerrado do Brasil Central em áreas de vegetação savânica típica – cerrado sensu stricto (cerrado s.s.) – e de formações florestais – cerradão e mata de galeria – considerando os efeitos da complexidade ambiental. A riqueza de espécies e os índices de diversidade “verdadeira” de Shannon e Simpson foram as métricas de diversidade usadas. Amostrei quatro áreas de cada fitofisionomia dispondo armadilhas no solo e sub-bosque nas três formações e também no dossel em cerradão e mata. Com esforço amostral total de 15744 armadilhas-noite em todo o estudo, capturei 348 indivíduos de 14 espécies. A amostragem de dossel em mata e cerradão incrementou suas riquezas de espécies, indicando efeito positivo da complexidade ambiental na maior riqueza dessas formações em relação a cerrado s.s.. Houve efeito da abundância das espécies nos padrões de diversidade das fitofisionomias. A mata teve maior diversidade do que cerradão e cerrado s.s. e estes não diferiram entre si pelo índice de Shannon. Já pelo índice de Simpson, mata teve maior diversidade, seguida por cerrado s.s. e por cerradão. Comunidades de cerradão tiveram similaridade de composição intermediária entre cerrado s.s. e mata de galeria, compartilhando espécies destas duas fitofisionomias. A diversidade beta entre fitofisionomias foi o componente com maior contribuição na diversidade regional, ao se considerar a riqueza e o índice de Shannon. No entanto, ela não diferiu do esperado pelo índice de Simpson, devido a uma mesma espécie ter sido a mais abundante em todas fitofisionomias. Por outro lado, o turnover de espécies entre comunidades de uma mesma fitofisionomia foi baixo (0,23) e entre fitofisionomias foi baixo/moderado (0,38), indicando pouco efeito da diversidade de fitofisionomias na diversidade de pequenos mamíferos no estudo. O presente estudo mostra a importância da amostragem de dossel de formações florestais e da consideração de múltiplas áreas de diferentes fitofisionomias em estudos de diversidade de pequenos mamíferos e traz informações que podem contribuir para a conservação de áreas do Cerrado, especialmente de cerradão. ______________________________________________________________________________ ABSTRACTThe diversity of animal groups may be related to the heterogeneity and/or to the environmental complexity. In the Cerrado domain, the high diversity level of small mammals has been related to the environmental heterogeneity and the influence of environmental complexity is still an open topic. The purpose of this study was to evaluate the partition of small-mammal diversity from a Cerrado region in central Brazil in areas of typical savannah – cerrado sensu stricto (cerrado s.s.) – and areas of forest vegetation – woodland savannah and gallery forest – considering the effects of the environmental complexity. The species richness and the Shannon’s and Simpson’s true diversity indexes were the diversity metrics used in the study. I selected four areas of each phytophysiognomic formation and trapped individuals on the ground and in the understorey levels at all phytophysiognomic formations. Additionally I also trapped individuals in the canopy at woodland savannahs and gallery forests. A total of 348 individuals of 14 species was caught in 15744 trap-nights all over the study. The trapping in the canopy of gallery forests and woodland savannahs increased the species richness, thus indicating a positive effect of the environmental complexity in the higher richness level of these formations compared to cerrado s.s. There was a marked effect of species abundance on the diversity patterns of the physiognomies. Gallery forest had higher diversity level than woodland savannah and cerrado s.s. and these two formations did not differ from each other considering the Shannon index. However, considering the Simpson index, gallery forest had the higher diversity level, followed by cerrado s.s. and after by woodland savannah. Woodland savannah areas had an intermediary compositional similarity with areas of cerrado s.s. and areas of gallery forest, harboring species of these formations. The beta diversity between physiognomies was the main component driving the regional diversity regarding richness of species and the Shannon index. However, considering the Simpson index this beta diversity did not differ from the expected values due to the fact that a single species was the most abundant in all the physiognomies. The turnover of species between communities was low (0,23) and it was low/moderate (0,38) between physiognomies. These results indicate that environmental heterogeneity has a minor effect on the small mammals diversity in the study. This study shows the importance of trapping small mammals in the canopy and of considering multiple areas of different physiognomies in studies of small mammals diversity and provides some information that may be applied for the conservation of Cerrado’s areas, specially the woodland savannahs

Milk and Byproducts Exports, Is It a Solution for Producers or a Problem for Consumers?

International Relations/Trade,

An implementation of the LHAR-CJ model with functional coefficients

This article aims to compare the forecast performance of the LHAR-CJ model, proposed in Corsi and Renò (2012) and a LHAR-CJ model with functional coefficients for a Vale return series. This new model, instead of estimating fixed coefficients for each variable in the autoregressive model, estimates a functional coefficient that is state dependent, where the state is represented by the lagged realized volatility. In other words, the coefficients are functions of the states of the response variable. We found out that, for this data, the functional coefficients model has a better forecast performance with the right smoothness parameter

The Effects of Leptin Replacement on Neural Plasticity

Leptin, an adipokine synthesized and secreted mainly by the adipose tissue, has multiple effects on the regulation of food intake, energy expenditure, and metabolism. Its recently-approved analogue, metreleptin, has been evaluated in clinical trials for the treatment of patients with leptin deficiency due to mutations in the leptin gene, lipodystrophy syndromes, and hypothalamic amenorrhea. In such patients, leptin replacement therapy has led to changes in brain structure and function in intra- and extrahypothalamic areas, including the hippocampus. Furthermore, in one of those patients, improvements in neurocognitive development have been observed. In addition to this evidence linking leptin to neural plasticity and function, observational studies evaluating leptin-sufficient humans have also demonstrated direct correlation between blood leptin levels and brain volume and inverse associations between circulating leptin and risk for the development of dementia. This review summarizes the evidence in the literature on the role of leptin in neural plasticity (in leptin-deficient and in leptin-sufficient individuals) and its effects on synaptic activity, glutamate receptor trafficking, neuronal morphology, neuronal development and survival, and microglial functio