适合度与近交衰退:同源四倍体和异源四倍体的比较研究
首发时间:2010-01-07
摘要:近交衰退指近交个体的适合度相对下降的现象,它是近亲繁殖的主要障碍。研究表明近交衰退的主要原因是近交增加纯和体中隐性有害等位基因的表达几率,自然选择会清除有害等位基因,所以相对于随机交配物种,近交物种具有较低的近交衰退。基因组倍性(多倍体)同样是影响近交衰退水平的重要因素,研究表明多倍体的近交衰退低于其祖先二倍体。本文研究了同源四倍体和异源四倍体适合度及近交衰退随世代的变化,结果显示,不论采取什么繁殖方式,亲代和子一代中同源四倍体的适合度都小于异源四倍体适合度,亲代和子一代中同源四倍体近交衰退都小于异源四倍体;同源四倍体中,亲代和子一代的适合度及近交衰退相等,异源四倍体中亲代近交衰退大于子一代。等位基因的显性水平与自然选择的程度对四倍体适合度与近交衰退的影响比交配系统更大。
关键词: 异源四倍体 同源四倍体 适合度 近交衰退 交配系统
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Fitness and inbreeding depression:differences between autotetraploid and allotetraploid
Abstract:Inbreeding depression is the decrease of offspring fitness after inbreeding and is one of the primary forces selecting against the evolution of self-fertilization. Researches suggest that inbreeding depression is mainly caused by the expression of recessive deleterious alleles as homozygotes whose frequency will increase because of self-fertilization or mating among relatives. Nature selection will purge the deleterious alleles, so compared with random mating species, highly selfing species may show less inbreeding depression. Polyploidy has also been hypothesized to affect magnitude of inbreeding depression, studies imply that polyploids exhibit less inbreeding depression than it’s diploidy ancestors. In this paper, we studied the differences of the relative fitness and inbreeding depression between autotetraploid and allotetraploid. The results inferenced that no matter what kind of reproductive method they may use, or how many generations have pasted since the tetraploid formed, autotetraploids have higher fitness than allotetraploid. The inbreeding depression of parental generation is higher than filial generation. The fitness and inbreeding depression of parental generation and filial generation are equal in autotetraploid,but for allotetraploid, inbreesding depression of parental generation is larger. Level of dominance and nature selection against deleterious allele is more important than mating system in changing the magnitude of fitness and inbreeding depression of polyploid.
Keywords: allopolyploidy autotetraploid fitness inbreeding depression mating system
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