Variance Effective Population Size for Dioecious Species

Vencovsky, Roland; Chaves, Lázaro José; Crossa, J.

doi:10.2135/cropsci2011.07.0360

Cited by 13 publications

(13 citation statements)

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“…By choosing one couple from each pair of parents, the variance of parental contributions is null S 2 k ¼ 0 À Á , and from Equation (1), N e ≈ 2N (Wright, 1938;Crow, 1954), which is twice the effective size of an unmanaged population with a Poisson distribution of family size. This is known as minimal inbreeding and it is the recommended procedure for applications in germplasm collection and regeneration in plants (see, for example, Vencovsky et al, 2012). However, effective sizes 42N can actually be obtained by population subdivision (Wright, 1943;Wang and Caballero, 1999) and other strategies, as shown below.…”

Section: Effective Population Size In Conservation Practicesmentioning

confidence: 99%

Prediction and estimation of effective population size

2016

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Effective population size (N e ) is a key parameter in population genetics. It has important applications in evolutionary biology, conservation genetics and plant and animal breeding, because it measures the rates of genetic drift and inbreeding and affects the efficacy of systematic evolutionary forces, such as mutation, selection and migration. We review the developments in predictive equations and estimation methodologies of effective size. In the prediction part, we focus on the equations for populations with different modes of reproduction, for populations under selection for unlinked or linked loci and for the specific applications to conservation genetics. In the estimation part, we focus on methods developed for estimating the current or recent effective size from molecular marker or sequence data. We discuss some underdeveloped areas in predicting and estimating N e for future research.Heredity ( INTRODUCTIONThe concept of effective population size, introduced by Sewall Wright (1931, 1933), is central to plant and animal breeding (Falconer and Mackay, 1996), conservation genetics (Frankham et al., 2010;Allendorf et al., 2013) and molecular variation and evolution (Charlesworth and Charlesworth, 2010), as it quantifies the magnitude of genetic drift and inbreeding in real-world populations. A substantial number of extensions to the basic theory and predictions were made since the seminal work of Wright, with main early developments by James Crow and Motoo Kimura (Kimura and Crow, 1963a;Crow and Kimura, 1970) and later by a list of contributors. Several review papers (Crow and Denniston, 1988;Caballero, 1994;Wang and Caballero, 1999;Nomura, 2005a) and population genetic books (Fisher, 1965;Wright, 1969;Ewens, 1979;Nagylaki, 1992) have summarised the existing theory in predicting the effective size of a population at different spatial and timescales under various inheritance modes and demographies. Comparatively, methodological developments (reviewed by Schwartz et al., 1999;Beaumont, 2003a;Wang, 2005;Palstra and Ruzzante, 2008;Luikart et al., 2010;Gilbert and Whitlock, 2015) in estimating the effective size of natural populations from genetic data lag behind but are accelerating in the past decade, thanks to the rapid developments of molecular biology.The classical developments of effective population size theory are based on the rate of change in gene frequency variance (genetic drift) or the rate of inbreeding. The effective population size is defined in reference to the Wright-Fisher idealised population, that is, a hypothetical population with very simplifying characteristics where genetic drift is the only factor in operation, and the dynamics of allelic and genotypic frequencies across generations merely depend on the population census (N) size. The effective size of a real population is then defined as the size of an idealised population, which would give rise to the rate of inbreeding and the rate of change in variance of gene frequencies actually observed in the population under consideration,

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Section: Effective Population Size In Conservation Practicesmentioning

confidence: 99%

Prediction and estimation of effective population size

2016

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“…The similar values for genetic diversity found between male and female individuals of M. coriacea may be the result of a balanced sex ratio in the species. Organisms with sexual reproduction tend to have a 1:1 sex ratio (Fisher 1930), deviations from which decrease the demographic effective population size (Vencovsky et al 2012). When genetic diversity is high and the sex ratio of a species is 1:1, the effects of genetic drift are minimized and do not cause an imbalance of genetic diversity between sexual morphs.…”

Section: Discussionmentioning

confidence: 99%

Genetic diversity of populations of the dioecious Myrsine coriacea (Primulaceae) in the Atlantic Forest

et al. 2018

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Although a species' sexual system may influence the genetic diversity of its populations in their natural environment, there have been few such studies involving indigenous species of the Atlantic Forest. Here we study Myrsine coriacea, a dioecious tree widely used in reforestation programs despite a lack of information about its natural interpopulation genetic variation. To address this knowledge gap, intra-and interpopulation genetic diversity were measured for male and female individuals of ten natural populations using ISSR markers. Greater intrapopulation genetic diversity indicated interpopulation gene flow, regardless of isolation and distance between populations. Multivariate analyses detected significant differences in genetic diversity between populations, but not between males and females, which indicates that genetic diversity did not differ between the two sex morphs. Distance between populations was unrelated to genetic diversity. Myrsine coriacea has not experienced a loss of genetic variability despite the characteristic segregated spatial distribution of its populations. These results suggest that obligatory cross-pollination and dispersal by birds may be important mechanisms for the maintenance of genetic diversity in natural populations of M. coriacea.

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“…O ganho genético em porcentagem (Gs%) com a seleção corresponde a: Vencovsky et al (2012) para espécies dioicas. Esse parâmetro foi estimado antes e após a aplicação das propostas de seleção descritas acima.…”

Section: Methodsunclassified

“…Isso ocorreu porque na fórmula de tamanho efetivo populacional (VENCOVSKY et al, 2012) foi considerado o mesmo número de indivíduos (750 indivíduos), intensidade de seleção (50%) e razão sexual para as duas procedências. A seleção aplicada afetou pouco o tamanho efetivo populacional do teste (Tabela 3).…”

Section: Procedência Caracteresunclassified

Desbaste seletivo em teste de procedências e progênies de Astronium fraxinifolium Schott com base na variabilidade genética

Cornacini¹,

Silva²,

Luz³

et al. 2017

Sci. For.

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ResumoO objetivo do trabalho foi propor um desbaste seletivo visando o manejo de um teste de procedências e progênies de Astronium fraxinifolium Schott com base no conhecimento da variabilidade genética, visando a conservação do seu potencial genético para fins comercial e ambiental. O teste foi instalado em 1996 em Selvíria-MS, no delineamento experimental de blocos completos casualizados. Foram usados 60 tratamentos (progênies) sendo 30 da procedência de Ilha Solteira-SP e 30 de Selvíria-MS com cinco repetições, 10 plantas por parcela, no espaçamento de 3 × 1,5 m, em plantio alternado com Jacaranda cuspidifolia Mart. Foram mensurados os caracteres DAP (diâmetro a altura do peito), ALT (altura total da planta), DMC (diâmetro médio de copa), FOR (forma de fuste) aos 18 anos após o plantio e a identificação do sexo das árvores. As estimativas de componentes de variância e parâmetros genéticos foram obtidas via modelo misto REML/BLUP (máxima verossimilhança restrita/melhor predição linear não viciada). Observou-se diferenças significativas entre procedências para os caracteres DAP e ALT, na análise de cada procedência houve diferenças significativas entre e dentro de progênies para todos os caracteres, exceto FOR. O coeficiente de herdabilidade em nível de média de progênies variou de 0,43 (FOR-MS) a 0,78 (DAP-MS) e a herdabilidade individual de 0,08 (FOR-MS) a 0,37 (DAP-MS). A acurácia foi alta (> 0,65) e os coeficientes de variação genética foram maiores que 5,6. As porcentagens de indivíduos em floração nas procedências de Ilha Solteira e Selvíria foram de 11% e 16%, respectivamente, com predominância de indivíduos com flores masculinas. A estratégia de seleção dentro de progênies, com seleção de 50% dos indivíduos com base no caráter DAP, revelou baixos ganhos na seleção, porém é a mais indicada para esse teste, pois possivelmente levará a uma menor alteração da variabilidade genética da população e diminuirá a probabilidade de cruzamentos entre parentes. Essa proposta de desbaste seletivo é mais adequada visto que a porcentagem de indivíduos em florescimento é baixa, o que inviabiliza a identificação sexual de todos os indivíduos do teste, e, consequentemente, as estimativas mais acuradas de parâmetros genéticos como o tamanho efetivo populacional.Palavras-chave: Conservação genética. Espécies nativas. Manejo florestal. Gonçalo alves. AbstractThe objective was to propose a management plan for provenance and progeny tests of Astronium fraxinifolium Schott. It is based on knowledge of genetic variability in an effort to promote the conservation of their genetic potential for commercial and environmental purposes. The test was originally conducted in 1996 in Selvíria, Mato Grosso do Sul (MS) Brazil using an experimental of randomized complete block design. We applied a total of 30 treatments (progenies) of provenance in Ilha Solteira, São Paulo (SP) and 30 treatments of provenance in Selvíria, MS each having five repetitions, 10 plants per plot, spaced 3m × 1.5m in alternate plantings with Jacaranda cuspidifolia...

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Variance Effective Population Size for Dioecious Species

Cited by 13 publications

References 27 publications

Prediction and estimation of effective population size

Prediction and estimation of effective population size

Genetic diversity of populations of the dioecious Myrsine coriacea (Primulaceae) in the Atlantic Forest

Desbaste seletivo em teste de procedências e progênies de Astronium fraxinifolium Schott com base na variabilidade genética

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