Data from: The impact of spatial scale and habitat configuration on patterns of trait variation and local adaptation in a wild plant parasite

Theory indicates that spatial scale and habitat configuration are fundamental for coevolutionary dynamics and how diversity is maintained in host–pathogen interactions. Yet, we lack empirical data to translate the theory to natural host–parasite systems. In this study, we conduct a multiscale cross-inoculation study using the specialist wild plant pathogen Podosphaera plantaginis on its host plant Plantago lanceolata. We apply the same sampling scheme to a region with highly fragmented (Åland) and continuous (Saaremaa) host populations. Although theory predicts higher parasite virulence in continuous regions, we did not detect differences in traits conferring virulence among the regions. Patterns of adaptation were highly scale dependent. We detected parasite maladaptation among regions, and among populations separated by intermediate distances (6.0–40.0 km) within the fragmented region. In contrast, parasite performance did not vary significantly according to host origin in the continuous landscape. For both regions, differentiation among populations was much larger for genetic variation than for phenotypic variation, indicating balancing selection maintaining phenotypic variation within populations. Our findings illustrate the critical role of spatial scale and habitat configuration in driving host–parasite coevolution. The absence of more aggressive strains in the continuous landscape, in contrast to theoretical predictions, has major implications for long-term decision making in conservation, agriculture, and public health.理论表明，空间尺度与生境配置是协同进化动态，以及宿主-病原体互作（host–pathogen interactions）中多样性维持机制的核心驱动要素。然而目前尚无实证数据，可将该理论推广至自然宿主-寄生物系统（host–parasite systems）。本研究以专性野生植物病原菌车前白粉菌（Podosphaera plantaginis）及其宿主长叶车前草（Plantago lanceolata）为研究对象，开展了多尺度交叉接种实验。我们采用统一的采样方案，分别对宿主种群高度破碎化的奥兰群岛（Åland）与种群连续分布的萨雷马岛（Saaremaa）两个区域进行采样。尽管理论预测连续分布区域中的寄生物毒力会更高，但我们并未在不同区域间检测到介导毒力的性状存在差异。适应性模式呈现出强烈的尺度依赖性：我们在区域间，以及破碎化区域内中等距离（6.0–40.0 km）分隔的种群间，均检测到了寄生物的适应性不良现象。与之相对，在连续分布的生境中，寄生物的表现并未随宿主来源地的不同而产生显著差异。对于两个区域而言，种群间的遗传变异分化程度均远高于表型变异分化，这表明种群内部存在维持表型变异的平衡选择作用。本研究结果阐明了空间尺度与生境配置在驱动宿主-寄生物协同进化过程中的关键作用。与理论预测相悖的是，连续分布生境中未出现毒力更强的菌株，这一发现对保护学、农学与公共卫生领域的长期决策具有重要意义。