Data from: Population structure of the invasive forest pathogen Hymenoscyphus pseudoalbidus

Understanding the genetic diversity and structure of invasive pathogens in source and introduced areas is crucial to reveal hidden biological aspects of an organism, to reconstruct the course of invasions and to establish effective control measures. Hymenoscyphus pseudoalbidus (anamorph: Chalara fraxinea) is an invasive and highly destructive fungal pathogen on common ash Fraxinus excelsior in Europe and occurs natively in east Asia. To get insights into the dispersal mechanism and the history of invasion, we used microsatellite markers and characterized the genetic structure and diversity of H. pseudoalbidus populations at three spatial levels: (i) in Europe; (ii) at the epidemic front and (iii) between Europe and Japan. The 1208 European strains form one large population as no evident structure was detected using Bayesian and multivariate clustering analysis. Only the distribution of genetic diversity in space, pairwise population differentiation (GST) and the spatial analysis of principal components revealed a faint geographic pattern around Europe. A significant allele deficiency in most European populations pointed to a recent genetic bottleneck whereas no pattern of isolation by distance was found. Populations from Japan harbored a higher genetic diversity and were genetically differentiated from European ones. Nevertheless, phylogenetic and network analysis clearly demonstrated that individuals from both regions are conspecific. Our data suggest that H. pseudoalbidus was introduced only once by a minimum of two individuals. The potential source region of H. pseudoalbidus is huge and further investigations are required for a more accurate localization of the source population.解析入侵病原菌在其原生来源地与入侵分布区的遗传多样性与群体遗传结构，对于揭示物种隐匿的生物学特性、重建入侵过程以及制定有效防控策略均具有关键意义。假挪威槭柱盘孢菌（*Hymenoscyphus pseudoalbidus*，无性型：*Chalara fraxinea*）是一种强入侵性、高破坏性的真菌病原菌，可侵染欧洲的欧洲白蜡树（*Fraxinus excelsior*），其自然原生分布区为东亚地区。为解析该病原菌的传播机制与入侵历史，本研究采用微卫星（microsatellite）标记技术，从三个空间尺度对*H. pseudoalbidus*的群体遗传结构与多样性展开分析：（1）欧洲全境范围；（2）病害流行前沿区域；（3）欧洲与日本种群之间。对1208株欧洲菌株的分析显示，通过贝叶斯（Bayesian）与多变量聚类分析未检测到显著的群体遗传结构，表明这些菌株构成一个统一的大种群。仅通过遗传多样性的空间分布、成对群体遗传分化系数（GST）以及主成分空间分析，才在欧洲范围内检测到微弱的地理分布模式。多数欧洲种群存在显著的等位基因缺失现象，提示该菌近期经历了遗传瓶颈效应，且未检测到距离隔离模式。日本种群的遗传多样性显著高于欧洲种群，且二者间存在显著遗传分化。但系统发育与网状进化分析结果均明确证实，两个区域的菌株隶属于同一物种。本研究数据表明，*H. pseudoalbidus*仅通过单次事件传入欧洲，且最小奠基种群个体数不少于2株。该病原菌的潜在原生来源地范围极广，未来需开展更多研究以精准定位其原生源种群。