URFM, INRAE, 84 000, Avignon, France.
Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK.
Heredity (Edinb). 2021 Mar;126(3):491-504. doi: 10.1038/s41437-020-00387-5. Epub 2020 Nov 23.
Understanding the ecological and evolutionary processes occurring during species range shifts is important in the current context of global change. Here, we investigate the interplay between recent expansion, gene flow and genetic drift, and their consequences for genetic diversity and structure at landscape and local scales in European beech (Fagus sylvatica L.) On Mont Ventoux, South-Eastern France, we located beech forest refugia at the time of the most recent population minimum, ~150 years ago, and sampled 71 populations (2042 trees) in both refugia and expanding populations over an area of 15,000 ha. We inferred patterns of gene flow and genetic structure using 12 microsatellite markers. We identified six plots as originating from planting, rather than natural establishment, mostly from local genetic material. Comparing genetic diversity and structure in refugia versus recent populations did not support the existence of founder effects: heterozygosity (He = 0.667) and allelic richness (Ar = 4.298) were similar, and F was low (0.031 overall). Still, significant spatial evidence of colonization was detected, with He increasing along the expansion front, while genetic differentiation from the entire pool (β) decreased. Isolation by distance was found in refugia but not in recently expanding populations. Our study indicates that beech capacities for colonization and gene flow were sufficient to preserve genetic diversity despite recent forest contraction and expansion. Because beech has long distance pollen and seed dispersal, these results illustrate a 'best case scenario' for the maintenance of high genetic diversity and adaptive potential under climate-change-related range change.
了解物种分布范围变化过程中的生态和进化过程，对于当前的全球变化背景非常重要。在这里，我们研究了近期扩张、基因流和遗传漂变之间的相互作用，以及它们对欧洲山毛榉（Fagus sylvatica L.）在法国东南部芒通山景观和局部尺度上遗传多样性和结构的影响。在芒通山，我们在最近一次种群最小值（约 150 年前）时定位了山毛榉森林避难所，并在 15000 公顷的区域内对避难所和扩张种群中的 71 个种群（2042 棵树）进行了采样。我们使用 12 个微卫星标记推断了基因流和遗传结构的模式。我们确定了六个来自种植而非自然建立的地段，主要来自当地的遗传物质。比较避难所和近期种群的遗传多样性和结构并不支持存在奠基者效应：杂合度（He=0.667）和等位基因丰富度（Ar=4.298）相似，F 很低（总体为 0.031）。尽管如此，仍检测到了显著的殖民化空间证据，随着扩张前沿的推进，He 增加，而与整个群体的遗传分化（β）降低。在避难所中发现了与距离隔离有关的遗传分化，但在最近扩张的种群中没有。我们的研究表明，尽管山毛榉的森林范围在最近有所收缩和扩张，但山毛榉的殖民化和基因流能力足以维持遗传多样性。由于山毛榉具有长距离的花粉和种子传播能力，这些结果说明了在与气候变化相关的分布范围变化下，维持高遗传多样性和适应潜力的“最佳情况”。
