ABSTRACT

To clarify the mechanisms underlying the maintenance of genetic diversity in long-lived forest tree populations, it is important to understand the influence of temporal variation in regeneration sites and its effect on population structure (i.e., nonrandom distribution of trees in spatial location and size) and the spatial genetic structure. Features of population structure in four different life stages (current-year seedlings, saplings, juveniles, and adults) were investigated in a natural population of Zelkova serrata. The genetic diversity and genetic structure of these life stages were evaluated using eight microsatellite markers, and the regeneration processes required for maintaining the genetic diversity of the adult tree population were inferred. Within a study plot, differences in spatial distribution among life stages and size classes, and significantly positive spatial autocorrelation of tree sizes (Km(r) statistic) at the adult stage were observed. Analysis of standardized measures of genetic differentiation showed a clear genetic difference among life stages (F’_ST = 0.095), with the adult stage exhibiting the highest allelic richness, the highest estimated effective number of contributing parents (N _eb), and the highest estimator of spatial genetic structure (S_p statistic). The adult stage may comprise many different cohorts (subpopulations), contributed by different compositions of parents, due to spatially and temporarily distinct regeneration events, and the resulting genetic heterogeneity would contribute to an increase in genetic diversity within the population.

摘要

为了阐明维持长寿林木种群遗传多样性的基础机制，重要的是要了解再生地点的时间变化的影响及其对种群结构的影响（即树木在空间位置和大小上的非随机分布）和空间遗传结构。在Zelkova s​​errata的自然种群中研究了四个不同生命阶段（当年的幼苗，幼树，幼虫和成虫）的种群结构特征。。使用八个微卫星标记评估了这些生命阶段的遗传多样性和遗传结构，并推断了维持成年树种群遗传多样性所需的再生过程。在一个研究图中，观察到成年阶段生命阶段和大小类别之间空间分布的差异以及树木大小的显着正空间自相关（Km（r）统计）。遗传分化的标准化测量分析表明之间生命阶段明确遗传差异（˚F ' _ST  = 0.095），与成年阶段表现出最高等位基因丰度，最高的估计有效若干贡献父母（Ñ _EB），以及空间遗传结构的最高估计值（S _p 统计量）。成年阶段可能包括许多不同的队列（亚群），由于空间和暂时不同的再生事件，它们由父母的不同组成贡献，并且由此产生的遗传异质性将有助于种群内遗传多样性的增加。