Data from: Understanding the recent colonization history of a plant pathogenic fungus using population genetic tools and Approximate Bayesian Computation

Understanding the processes by which new diseases are introduced in previously healthy areas is of major interest in elaborating prevention and management policies as well as in understanding the dynamics of pathogen diversity at large spatial scale. In this study, we aimed to decipher the dispersal processes that have led to the emergence of the plant pathogenic fungus Microcyclus ulei, which is responsible for the South American Leaf Blight (SALB) that has affected rubber trees across Latin America since the beginning of the twentieth century. As only imprecise historical information is available, the study of population evolutionary history based on population genetics appeared most appropriate. The distribution of genetic diversity in a continental sampling of four countries (Brazil, Ecuador, Guatemala and French Guiana) was studied using a set of 16 microsatellite markers developed specifically for this purpose. A very strong genetic structure was found (Fst = 0.70), demonstrating that there has been no regular gene flow between Latin American M. ulei populations. Strong bottlenecks probably occurred at the foundation of each population. The most likely scenario of colonization identified by the Approximate Bayesian Computation (ABC) method implemented in DIYABC suggested two independent sources from the Amazonian endemic area. The Brazilian, Ecuadorian and Guatemalan populations might stem from serial introductions through human-mediated movement of infected plant material from an unsampled source population, whereas the French Guiana population seems to have arisen from an independent colonization event through spore dispersal.解析新发疫病传入既往无疫区域的过程，对于制定疫病防控与管理政策、探究大空间尺度下病原多样性的动态变化均具有重要意义。本研究旨在解析引发植物病原真菌橡胶南美叶枯病菌（Microcyclus ulei）种群扩散的具体过程——该病菌导致的南美叶枯病（South American Leaf Blight, SALB）自20世纪初起，已对整个拉丁美洲的橡胶树造成严重危害。由于仅能获取不精确的历史记录，基于种群遗传学开展种群演化历史研究成为最为合适的研究手段。本研究针对覆盖巴西、厄瓜多尔、危地马拉及法属圭亚那4个国家的大陆尺度采样群体，利用专为该研究开发的16对微卫星标记，分析了其遗传多样性的分布格局。结果显示种群存在极强的遗传结构分化（Fst=0.70），表明拉丁美洲各地的橡胶南美叶枯病菌种群之间不存在常规的基因交流。各病菌种群的奠基过程大概率经历了强烈的瓶颈效应。通过DIYABC软件实现的近似贝叶斯计算（Approximate Bayesian Computation, ABC）方法，本研究鉴定出最可信的定殖场景：该病菌存在两个独立的疫源，均源自亚马逊流域的原生疫区。巴西、厄瓜多尔及危地马拉的病菌种群可能源自未被采样的源种群通过人类携带带菌植物材料实现的连续引种事件，而法属圭亚那的种群则似乎是通过孢子扩散完成的独立定殖事件。