Land-use conversion and habitat loss and degradation are among the factors affecting populations and species genetic integrity. Understanding how these factors govern the genetic structure of threatened plant populations is essential to design efficient conservation strategies. Here we analyze how environmental correlates, geographic location and anthropogenic disturbance (at local, landscape and regional scales) relate to population differentiation and genetic diversity of a keystone semiarid long-lived shrub, Ziziphus lotus. The European range of this species is restricted mainly to the southeast of the Iberian Peninsula (> 90%) but its area has shrunk considerably as a consequence of intensive agriculture and urban expansion since the 1950s. We characterize its genetic diversity and structure across the Iberian Peninsula with microsatellite markers, considering 21 populations. All populations showed high and relatively similar values of genetic diversity (mean/pop: H_o = 0.54; H_e = 0.55; A_R = 3.59). Three main genetic clusters were defined by clustering analyses corresponding largely to west, central (core) and east of its distribution. Molecular variance analysis revealed that 87.3% of genetic variation was grouped within populations, 5% among populations and 7% between regions. Geographic location (37.88%) has stronger correlation with population genetic differences than landscape characteristics (5.82%). Natural habitat cover at the landscape level was the only environmental variable associated with F_ST population differences. The detected population genetic patterns are probably related primarily to historical gene flow and secondarily to intensive land-use change of this area in the last 60 years. Our results suggest that, although the long-lived and resprouting strategy of the species is buffering the erosion of genetic diversity at population and regional level, there are already genetic consequences of landscape degradation, which could be aggravated in the future.

土地用途的转换以及栖息地的丧失和退化是影响种群和物种遗传完整性的因素。了解这些因素如何控制受威胁植物种群的遗传结构对于设计有效的保护策略至关重要。在这里，我们分析了环境相关性，地理位置和人为干扰（在本地，景观和区域范围内）与梯形半干旱长寿灌木紫芝莲的种群分化和遗传多样性之间的关系。。该物种在欧洲的分布范围主要限于伊比利亚半岛的东南部（> 90％），但由于1950年代以来的集约化农业和城市扩张，其面积已大大缩小。考虑到21个种群，我们使用微卫星标记物表征了伊比利亚半岛整个地区的遗传多样性和结构。所有种群均显示出较高且相对相似的遗传多样性值（平均值/流行：H _o  = 0.54；H _e  = 0.55；A _R = 3.59）。通过聚类分析确定了三个主要的遗传簇，主要对应于其分布的西部，中部（核心）和东部。分子方差分析表明，遗传变异的87.3％被归为种群，种群之间为5％，区域之间为7％。地理位置（37.88％）与种群遗传差异的相关性强于景观特征（5.82％）。景观层面的自然栖息地覆盖是与F _ST相关的唯一环境变量人口差异。所发现的种群遗传模式可能主要与历史基因流有关，其次与最近60年该地区土地利用的密集变化有关。我们的结果表明，尽管该物种的长期生存和重新萌芽策略正在缓冲种群和区域一级的遗传多样性侵蚀，但已经存在景观退化的遗传后果，将来可能会加剧这种恶化。