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      Variabilidade Genética em Populações Naturais de Cassia grandis L. f. Translated title: Genetic Variability in Natural Populations of Cassia grandis L. F.

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          RESUMO O delineamento de estratégias para a conservação genética de uma espécie requer o conhecimento de aspectos ecológicos e genéticos de suas populações. Assim, este trabalho foi realizado com o objetivo de caracterizar, por meio de marcadores isoenzimáticos, populações naturais de Cassia grandis L.f. A diversidade genética foi analisada a partir das frequências alélicas ( P ^ i j ) e dos Índices de diversidade: Heterozigose média observada ( H ^ 0 ) e esperada ( H ^ e ), número médio de alelos por loco ( A ^ ) e porcentagem de locos polimórficos ( P ^); e a estrutura genética por meio das estatísticas F de Wright. Foram estimados o fluxo gênico, o tamanho efetivo das populações e a população mínima viável a curto e longo prazo. Com base nos resultados observados pode-se concluir que as populações estudadas de C. grandis estão estruturadas, o que pode ser comprovado pela observação de alelos raros e exclusivos e da alta diversidade genética entre as mesmas.

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          ABSTRACT The design of strategies for genetic conservation requires knowledge of the ecologic and genetics aspects of the target species populations. This work aimed to characterize genetically natural populations of Cassia grandis L. F. using isozymes. Genetic diversity was analyzed by allele frequencies ( P ^ i j ) and the following diversity indexes: observed ( H ^ e ) and expected ( H ^ e )average heterozygosity, average number of alleles per locus ( A ^ ) and percentage of polymorphic loci ( P ^); and the genetic structure of populations by Wright's statistics. We estimated gene flow, population effective size and the minimum viable population in the short and long time. The observed results conclude that the studied populations of C. grandis are structured, which can be demonstrated by observation of rare and exclusive alleles, and high genetic diversity among them.

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          Most cited references 28

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          The genetical structure of populations.

           S. Wright (1951)
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            Group selection for a polygenic behavioral trait: estimating the degree of population subdivision.

             Yanick Crow,  K. Aoki (1984)
            For assessing the degree of population subdivision, and therefore the extent to which group selection might favor an altruistic trait, an appropriate measure is Nei's GST, defined by (F0-F)/(1-F). F0 is the probability that two alleles drawn from the same group are identical in state and F is the probability for two alleles drawn at random from the entire population. These probabilities can be assessed from molecular polymorphisms. GST has a number of properties that make it useful for empirical studies. When the mutation rate is small relative to the migration rate and the reciprocal of the group size, GST depends mainly on the absolute number of migrants per generation, moves rapidly to near equilibrium, and is independent of the number of alleles. The relative homogenizing effect of migration in the island and stepping-stone models is not as different as might be expected; one immigrant chosen randomly from the rest of the population is only one to two times as effective as one from a neighboring group, appreciably exceeding 2 only when there are 1000 or more groups. The use of molecular data to estimate the degree of population subdivision may permit testable predictions of the extent of altruistic behavior.
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              Assessing minimum viable population size: Demography meets population genetics.

               L Nunney,  K. Campbell (1993)
              The discussion of a population's minimum viable size provides a focus for the study of ecological and genetic factors that influence the persistence of a threatened population. There are many causes of extinction and the fate of a specific population cannot generally be predicted. This uncertainty has been dealt with in two ways: through stochastic demographic models to determine how to minimize extinction probabilities; and through population genetic theory to determine how best to maintain genetic variation, in the belief that the ability to evolve helps buffer a population against the unknown. Recent work suggests that these two very different approaches lead to very similar conclusions, at least under panmictic conditions. However, defining the ideal spatial distribution for an endangered species remains an important challenge. Copyright © 1993. Published by Elsevier Ltd.

                Author and article information

                Role: ND
                Role: ND
                Role: ND
                Floresta e Ambiente
                Floresta Ambient.
                Instituto de Florestas da Universidade Federal Rural do Rio de Janeiro (Seropédica, RJ, Brazil )
                August 2018
                : 25
                : 4
                Viçosa Minas Gerais orgnameUniversidade Federal de Viçosa orgdiv1Departamento de Fitotecnia Brazil
                São Cristóvão orgnameUniversidade Federal de Sergipe orgdiv1Departamento de Ciências Florestais Brazil
                São Cristóvão orgnameUniversidade Federal de Sergipe orgdiv1Departamento de Engenharia Agronômica Brazil

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