Conservação genética de populações de Cryptocarya moschata Nees (Lauraceae) na Mata Atlântica do estado de São Paulo
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Data
1999-10-01
Autores
MORAES, PEDRO LUÍS RODRIGUES DE [UNESP]
MONTEIRO, REINALDO [UNESP]
VENCOVSKY, ROLAND
Título da Revista
ISSN da Revista
Título de Volume
Editor
Sociedade Botânica de São Paulo
Resumo
Através da análise de 18 locos isoenzimáticos polimórficos, foram estimadas as freqüências alélicas referentes a 214 indivíduos adultos de quatro populações naturais de Cryptocarya moschata de duas regiões do estado de São Paulo. Com base nas heterozigosidades observadas e esperadas, foram obtidas estimativas das estatísticas F de Wright. Para fins de comparação, utilizou-se também o método da análise da variância para estimação dos parâmetros correspondentes F = FIT, qP= FST e f = FIS. Os dois métodos forneceram resultados bastante concordantes: IT = 0,142; ST = 0,140; IS = 0,002 e = 0,116; P = 0,123 e = 0,008, indicando que os indivíduos dentro das populações devem ser panmíticos e que a diversidade entre populações é bastante alta, sendo similar à que se espera para famílias com estruturação de meios-irmãos. Calculando P com as populações tomadas duas a duas, notou-se tendência de P crescer com a distância geográfica o que sugere tendência de isolamento pela distância. O fluxo gênico foi estimado em 0,9 indivíduos por geração, o que corrobora a pronunciada diferenciação populacional encontrada. Devido ao valor negligível encontrado de IS, o tamanho efetivo de variância de cada população é equivalente ao número de indivíduos amostrados. As estratégias de manejo e conservação necessárias para a preservação da alta variabilidade genética intrapopulacional de C. moschata implicam na manutenção de populações com número grande de indivíduos. Além disso, para a preservação da espécie como um todo, a manutenção de muitas populações provavelmente é necessária.
This paper was aimed at studying the genetic structure of populations of Cryptocarya moschata and proposing conservation strategies for the species. Allozyme data of 18 polymorphic loci were collected from 214 trees sampled from four natural populations located in two regions of the State of São Paulo, Brazil. Estimates of Wright's F statistics were computed on the basis of observed and expected heterozygosities. The analysis of variance, pooled over loci and alleles, was also used to compare corresponding estimates of F (= FIT), qP (= FST) and f (= FIS). Both methods provided similar results with IT = 0.142, ST = 0.140, IS = 0.002 and = 0.116, P = 0.123 and = 0.008. Results indicated that individuals within populations are probably panmitic. Diversity among populations was very high, similar to what would be expected for groups of plants with a half-sib family structure. Estimates of P, obtained for populations taken two at a time, indicated that diversity tended to increase with distance and suggested that isolation by distance is a factor to be considered. An estimated gene flow of 0.9 migrants per generation corroborated to the pronounced divergence found among populations. Due to the negligible IS value found, the variance effective size for each population is equivalent to its sampling number. In this case, management and conservation strategies aimed at preserving high intrapopulation genetic variation, will imply in the maintenance of large populations. In addition, due to the relatively large divergence detected among populations, the preservation of the species as a whole will also require the maintenance of many such populations.
This paper was aimed at studying the genetic structure of populations of Cryptocarya moschata and proposing conservation strategies for the species. Allozyme data of 18 polymorphic loci were collected from 214 trees sampled from four natural populations located in two regions of the State of São Paulo, Brazil. Estimates of Wright's F statistics were computed on the basis of observed and expected heterozygosities. The analysis of variance, pooled over loci and alleles, was also used to compare corresponding estimates of F (= FIT), qP (= FST) and f (= FIS). Both methods provided similar results with IT = 0.142, ST = 0.140, IS = 0.002 and = 0.116, P = 0.123 and = 0.008. Results indicated that individuals within populations are probably panmitic. Diversity among populations was very high, similar to what would be expected for groups of plants with a half-sib family structure. Estimates of P, obtained for populations taken two at a time, indicated that diversity tended to increase with distance and suggested that isolation by distance is a factor to be considered. An estimated gene flow of 0.9 migrants per generation corroborated to the pronounced divergence found among populations. Due to the negligible IS value found, the variance effective size for each population is equivalent to its sampling number. In this case, management and conservation strategies aimed at preserving high intrapopulation genetic variation, will imply in the maintenance of large populations. In addition, due to the relatively large divergence detected among populations, the preservation of the species as a whole will also require the maintenance of many such populations.
Descrição
Palavras-chave
Genetic structure, effective population size, gene flow, Cryptocarya moschata
Como citar
Brazilian Journal of Botany. Sociedade Botânica de São Paulo, v. 22, p. 237-248, 1999.