Metapopulation Research Group, Department of Biosciences, University of Helsinki, PO Box 65 (Viikinkaari 1), University of Helsinki, FI-00014, Finland.
Evolution. 2014 Jan;68(1):176-89. doi: 10.1111/evo.12239. Epub 2013 Sep 11.
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，空间尺度和生境配置对于共进化动态以及宿主-病原体相互作用中多样性如何维持至关重要。然而，我们缺乏将理论转化为自然宿主-寄生虫系统的经验数据。在这项研究中，我们使用专性野生植物病原体 Podosphaera plantaginis 对其宿主植物 Plantago lanceolata 进行了多尺度交叉接种研究。我们将相同的采样方案应用于具有高度破碎（Åland）和连续（Saaremaa）宿主种群的区域。尽管理论预测在连续区域中寄生虫的毒力更高，但我们没有检测到不同区域之间赋予毒力的特征存在差异。适应模式高度依赖于尺度。我们在不同区域以及在破碎区域内间隔 6.0-40.0 公里的中间距离的种群之间检测到寄生虫适应不良。相比之下，寄生虫在连续景观中的表现与宿主起源没有显著差异。对于两个区域，种群之间的分化在遗传变异方面远大于表型变异，表明平衡选择维持了种群内的表型变异。我们的研究结果说明了空间尺度和生境配置在驱动宿主-寄生虫共进化方面的关键作用。在连续景观中缺乏更具攻击性的菌株，这与理论预测相反，这对保护、农业和公共卫生领域的长期决策具有重大意义。
