Data from: Genetic structure and diversity of the endangered fir tree of Lebanon (Abies cilicica Carr.): implications for conservation

The threatened conifer Abies cilicica currently persists in Lebanon in geographically isolated forest patches. The impact of demographic and evolutionary processes on population genetic diversity and structure were assessed using 10 nuclear microsatellite loci. All remnant 15 local populations revealed a low genetic variation but a high recent effective population size. FST-based measures of population genetic differentiation revealed a low spatial genetic structure, but Bayesian analysis of population structure identified a significant Northeast-Southwest population structure. Populations showed significant but weak isolation-by-distance, indicating non-equilibrium conditions between dispersal and genetic drift. Bayesian assignment tests detected an asymmetric Northeast-Southwest migration involving some long-distance dispersal events. We suggest that the persistence and Northeast-Southwest geographic structure of Abies cilicica in Lebanon is the result of at least two demographic processes during its recent evolutionary history: (1) recent migration to currently marginal populations and (2) local persistence through altitudinal shifts along a mountainous topography. These results might help us better understand the mechanisms involved in the species response to expected climate change.

濒危针叶树种西里西亚冷杉（Abies cilicica）目前仅在黎巴嫩残存于地理隔离的林分斑块中。本研究利用10个核微卫星位点（nuclear microsatellite loci），探究了种群动态与演化过程对种群遗传多样性及遗传结构的影响。所有现存的15个局域种群均表现出较低的遗传变异水平，但近期有效种群规模（effective population size）较高。基于FST（固定指数，Fixation Index）的种群遗传分化指标显示空间遗传结构较弱，而种群结构的贝叶斯分析（Bayesian analysis）则揭示了显著的东北-西南方向种群分化格局。种群间表现出显著但微弱的距离衰减隔离（isolation-by-distance）现象，表明扩散与遗传漂变之间处于非平衡状态。贝叶斯归属分析（Bayesian assignment tests）检测到了不对称的东北-西南方向基因流，涉及多次长距离扩散事件。我们认为，西里西亚冷杉在黎巴嫩的残存现状及其东北-西南方向的地理格局，是其近期演化历史中至少两类种群动态过程共同作用的结果：(1) 向当前边缘种群的近期基因迁移；(2) 沿山地地形通过海拔位移实现局域存续。本研究结果有助于更深入理解该物种应对预期气候变化的潜在机制。