The study of population genetic structure congruence between hosts and pathogens gives important insights into their shared phylogeographic and coevolutionary histories. We studied the population genetic structure of castrating anther-smut fungi (Microbotryum genus) and of their host plants, the Silene nutans species complex, and the morphologically and genetically close S. italica, which can be found in sympatry. Phylogeographic population genetic structure related to persistence in separate glacial refugia has been recently revealed in the S. nutans plant species complex across Western Europe, identifying several distinct lineages. We genotyped 171 associated plant-pathogen pairs of anther-smut fungi and their host plant individuals using microsatellite markers and plant chloroplastic SNPs. We found clear differentiation between fungal populations parasitizing S. nutans and S. italica plants. The population genetic structure of fungal strains parasitizing the S. nutans plant species complex mirrored the host plant genetic structure, suggesting that the pathogen was isolated in glacial refugia together with its host and/or that it has specialized on the plant genetic lineages. Using random forest approximate Bayesian computation (ABC-RF), we found that the divergence history of the fungal lineages on S. nutans was congruent with the one previously inferred for the host plant and likely occurred with ancient but no recent gene flow. Genome sequences confirmed the genetic structure and the absence of recent gene flow between fungal genetic lineages. Our analyses of host-pathogen individual pairs contribute to a better understanding of co-evolutionary histories between hosts and pathogens in natural ecosystems, in which such studies are still scarce.

中文翻译：

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花药曲霉真菌及其寄主植物Silene italica和Silene nutans种复合体的一致种群遗传结构和发散历史。

对宿主和病原体之间种群遗传结构一致性的研究为他们共同的系统地理学和共同进化史提供了重要的见识。我们研究了cast割花药-真菌（Microbotryum属）及其寄主植物，Silene nutans物种复合体以及形态和遗传上接近的S.italica的种群遗传结构，它们可以在共生体中找到。最近在整个西欧的纳豆链球菌植物物种复合物中发现了与持久存在于单独的冰川避难所有关的植物种群遗传结构，从而确定了几个不同的谱系。我们使用微卫星标记和植物叶绿体SNP对171个相关的植物病原体对花药曲霉真菌及其宿主植物个体进行了基因分型。我们发现寄生于S. nutans和S. italica植物的真菌种群之间有明显的区别。寄生于S. nutans植物种复合体的真菌菌株的种群遗传结构反映了宿主植物的遗传结构，这表明该病原体与其宿主一起在冰川避难所中被分离，和/或专门针对植物遗传谱系。使用随机森林近似贝叶斯计算（ABC-RF），我们发现坚果链球菌上的真菌谱系的发散历史与先前针对寄主植物推断的真菌谱系一致，并且可能发生于古老但近期没有基因流。基因组序列证实了真菌的遗传谱系之间的遗传结构和最近的基因流的缺乏。