Land use change reduced calcareous grasslands throughout Europe during the last decades. Subsequent fragmentation and habitat deterioration led, moreover, to a massive biodiversity decline. To counteract this alarming development, a clear understanding of genetic variation patterns, as fundamental level of biodiversity, becomes inevitable. The aim of our study was to identify the drivers of genetic variation in common calcareous grassland plant species. More specifically, we tested whether genetic diversity or differentiation of Asperula cynanchica, Campanula rotundifolia, and Linum catharticum depend on habitat age, landscape structure, habitat quality, and/or population size. We investigated 912 individuals, 304 per study species, from 19 calcareous grasslands across the Swabian Alb in Baden-Wurttemberg (Germany) using AFLP analyses. We observed no significant influence of habitat age on genetic diversity and differentiation. Habitat quality also had no impact on genetic diversity and population size only showed weak effects. However, genetic diversity strongly depended on landscape structure represented by distance to the nearest settlement, total area of surrounding calcareous grasslands, and their connectivity. Migratory sheep herding is considered as main land use in calcareous grasslands on the Swabian Alb and thus, landscape structures in the study region may describe movement patterns of grazing livestock. In this study, genetic variation in calcareous grassland populations was strongly affected by surrounding landscape structures and subsequent grazing patterns. Therefore, we assume that moderate grazing intensities over the long term may increase levels of genetic diversity, whereas periods of overgrazing or abandonment could lower genetic diversity.

中文翻译：

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周围景观结构，而不是栖息地年龄，驱动典型钙质草原植物物种的遗传变异

在过去的几十年里，土地利用的变化减少了整个欧洲的钙质草原。此外，随后的破碎化和栖息地恶化导致了生物多样性的大规模下降。为了抵消这种令人担忧的发展，对作为生物多样性基本水平的遗传变异模式的清晰理解变得不可避免。我们研究的目的是确定常见钙质草地植物物种遗传变异的驱动因素。更具体地说，我们测试了 Asperula cynanchica、Campanula rotundifolia 和 Linum catharticum 的遗传多样性或分化是否取决于栖息地年龄、景观结构、栖息地质量和/或种群规模。我们使用 AFLP 分析调查了 912 个人，每个研究物种 304 人，来自巴登-符腾堡州（德国）施瓦本白山的 19 个钙质草原。我们观察到栖息地年龄对遗传多样性和分化没有显着影响。栖息地质量对遗传多样性也没有影响，种群规模仅表现出微弱的影响。然而，遗传多样性强烈依赖于以距最近聚居地的距离、周围钙质草地总面积及其连通性为代表的景观结构。迁徙绵羊放牧被认为是施瓦本白云上石灰质草原的主要土地利用，因此，研究区域的景观结构可以描述放牧牲畜的运动模式。在这项研究中，钙质草地种群的遗传变异受到周围景观结构和随后的放牧模式的强烈影响。所以，