Within-Population Genetic Structure in Beech (Fagus sylvatica L.) Stands Characterized by Different Disturbance Histories: Does Forest Management Simplify Population Substructure?

The fine-scale assessment of both spatially and non-spatially distributed genetic variation is crucial to preserve forest genetic resources through appropriate forest management. Cryptic within-population genetic structure may be more common than previously thought in forest tree populations, which has strong implications for the potential of forests to adapt to environmental change. The present study was aimed at comparing within-population genetic structure in European beech (Fagus sylvatica L.) plots experiencing different disturbance levels. Five plot pairs made up by disturbed and undisturbed plots having the same biogeographic history were sampled throughout Europe. Overall, 1298 individuals were analyzed using four highly polymorphic nuclear microsatellite markers (SSRs). Bayesian clustering within plots identified 3 to 11 genetic clusters (within-plot θST ranged from 0.025 to 0.124). The proportion of within-population genetic variation due to genetic substructuring (FCluPlot = 0.067) was higher than the differentiation among the 10 plots (FPlotTot = 0.045). Focusing on the comparison between managed and unmanaged plots, disturbance mostly explains differences in the complexity of within-population genetic structure, determining a reduction of the number of genetic clusters present in a standardized area. Our results show that: i) genetic substructuring needs to be investigated when studying the within-population genetic structure in forest tree populations, and ii) indices describing subtle characteristics of the within-population genetic structure are good candidates for providing early signals of the consequences of forest management, and of disturbance events in general.

对空间分布与非空间分布的遗传变异开展精细尺度评估，对于通过合理森林管理保护森林遗传资源至关重要。林木种群中，种群内隐秘遗传结构的出现频率可能高于此前预期，这对森林适应环境变化的潜力具有深远影响。本研究旨在比较不同干扰水平下欧洲山毛榉（Fagus sylvatica L.）样地的种群内遗传结构。研究在欧洲全境布设了5对样地，每对均由具有相同生物地理历史的受干扰样地与未受干扰样地组成，共对1298个个体进行了分析，所用标记为4个高度多态的核微卫星标记（SSRs）。对各单样地开展贝叶斯聚类分析，共识别出3至11个遗传簇（样地内θ_ST取值范围为0.025至0.124）。由遗传亚结构导致的种群内遗传变异占比（FCluPlot = 0.067）高于10个样地间的遗传分化水平（FPlotTot = 0.045）。聚焦经营样地与未经营样地的对比分析，干扰程度主要解释了种群内遗传结构复杂度的差异，导致标准化面积内遗传簇的数量显著减少。本研究结果表明：其一，在研究林木种群的种群内遗传结构时，需对遗传亚结构进行系统性考察；其二，能够反映种群内遗传结构细微特征的指标，可作为揭示森林管理乃至一般干扰事件后果的早期信号的优质候选指标。