102 resultados para Directional gene flow


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The Brazilian fauna has been constantly threatened by deforestation and forest fragmentation. As a result, many populations become isolated and small which negatively impacts their genetic diversity, putting them at a higher risk of extinction than large and stable populations. The aim of this work was to estimate the genetic diversity of white-lipped peccaries (Tayassu pecari) in the region of Taboco (Corguinho, MS), a fragmented area; and to compare these estimates with that obtained previously for two populations from Brazilian Pantanal, which is considered a relatively well-preserved biome and where the species is not threatened. A total of 18 blood and 72 hair samples of white-lipped peccaries had their DNA extracted and amplified for five polymorphic microsatellite loci. With the individuals identified, genetic diversity indicators (such as number of alleles, allelic richness, expected end and observed) and the inbreeding coefficient FIS were calculated. In addition, to verify if the population suffered a recent population bottleneck, we used the tests implemented in the program Bottleneck. The population of Taboco showed no evidence of recent population bottleneck (p > 0.05) or inbreeding (FIS = 0.008; p > 0.022). In addition, the levels of genetic diversity in this population (mean number of alleles = 2.60; mean allelic richness = 2.56 mean observed and expected heterozygosities = 0.45 and 0.47, respectively) were statistically similar to those found previously for the two populations from Pantanal (p > 0,05); although the region of Taboco is more impacted than the Pantanal. Even though we showed no evidence of loss of genetic diversity, it does not mean that the population is not suffering with fragmentation; but that there was not sufficient time to evidence the genetic changes. In addition, may be occurring gene flow with populations of nearby fragments, which is maintaining... (Complete abstract click electronic access below)

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Pós-graduação em Agronomia (Genética e Melhoramento de Plantas) - FCAV

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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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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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Population genetics theory predicts loss in genetic variability because of drift and inbreeding in isolated plant populations; however, it has been argued that long-distance pollination and seed dispersal may be able to maintain gene flow, even in highly fragmented landscapes. We tested how historical effective population size, historical migration and contemporary landscape structure, such as forest cover, patch isolation and matrix resistance, affect genetic variability and differentiation of seedlings in a tropical palm (Euterpe edulis) in a human-modified rainforest. We sampled 16 sites within five landscapes in the Brazilian Atlantic forest and assessed genetic variability and differentiation using eight microsatellite loci. Using a model selection approach, none of the covariates explained the variation observed in inbreeding coefficients among populations. The variation in genetic diversity among sites was best explained by historical effective population size. Allelic richness was best explained by historical effective population size and matrix resistance, whereas genetic differentiation was explained by matrix resistance. Coalescence analysis revealed high historical migration between sites within landscapes and constant historical population sizes, showing that the genetic differentiation is most likely due to recent changes caused by habitat loss and fragmentation. Overall, recent landscape changes have a greater influence on among-population genetic variation than historical gene flow process. As immediate restoration actions in landscapes with low forest amount, the development of more permeable matrices to allow the movement of pollinators and seed dispersers may be an effective strategy to maintain microevolutionary processes.

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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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Pós-graduação em Agronomia (Horticultura) - FCA