Data from: Genetic signatures of variation in population size in a native fungal pathogen after the recent massive plantation of its host tree

Historical fluctuations in forests’ distribution driven by past climate changes and anthropogenic activities can have large impacts on the demographic history of pathogens that have a long co-evolution history with these host trees. Using a population genetic approach, we investigated that hypothesis by reconstructing the demographic history of Armillaria ostoyae, one of the major pathogens of the maritime pine (Pinus pinaster), in the largest monospecific pine planted forest in Europe (south-western France). Genetic structure analyses and approximate Bayesian computation approaches revealed that a single pathogen population underwent a severe reduction in effective size (12 times lower) 1,080 – 2,080 generations ago, followed by an expansion (four times higher) during the last four generations. These results are consistent with the history of the maritime pine forest in the region characterized by a strong recession during the last glaciation (~19,000 years ago) and massive plantations during the second half of the 19th century. Results suggest that recent and intensive plantations of a host tree population have offered the opportunity for a rapid spread and adaptation of their pathogens.由古气候变化与人类活动驱动的森林分布历史波动，可对与宿主树木存在长期共演化历史的病原体的种群历史（demographic history）产生显著影响。本研究采用种群遗传学方法（population genetic approach），以欧洲规模最大的单优人工松林（法国西南部）为研究对象，通过重构海岸松（Pinus pinaster）主要病原菌之一的小蜜环菌（Armillaria ostoyae）的种群历史，对上述假说展开验证。种群遗传结构分析与近似贝叶斯计算（approximate Bayesian computation）结果显示，该病原菌的单一种群在1080至2080个世代前经历了有效种群规模（effective size）的剧烈缩减（仅为原规模的1/12），随后在最近4个世代中出现种群扩张（为原规模的4倍）。上述结果与该区域海岸松松林的演化历史高度契合：末次冰期（约19000年前）该区域海岸松种群经历了严重衰退，而19世纪下半叶则开展了大规模人工造林。研究结果表明，宿主种群近期开展的高密度人工造林，为其病原菌的快速扩散与适应性演化提供了有利契机。