Foliar fungi (defined as all fungal species in leaves after surface sterilization; hereafter, ‘FF’) are of great importance to host plant growth and health, and can also affect ecosystem functioning. Despite this importance, few studies have explicitly examined the role of host filtering in shaping local FF communities, and we know little about the differences of FF community assembly between symptomatic (caused by fungal pathogens) and asymptomatic leaves, and whether there is phylogenetic congruence between host plants and FF. We examined FF communities from 25 host plant species (for each species, symptomatic and asymptomatic leaves, respectively) in an alpine meadow of the Tibetan Plateau using MiSeq sequencing of ITS1 gene biomarkers. We evaluated the phylogenetic congruence of FF–plant interactions based on cophylogenetic analysis, and examined α- and β-phylogenetic diversity indices of the FF communities. We found strong support for phylogenetic congruence between host plants and FF for both asymptomatic and symptomatic leaves, and a host-caused filter appears to play a major role in shaping FF communities. Most importantly, we provided independent lines of evidence that host environmental filtering (caused by fungal infections) outweighs competitive exclusion in driving FF community assembly in symptomatic leaves. Our results help strengthen the foundation of FF community assembly by demonstrating the importance of host environmental filtering in driving FF community assembly.

叶真菌（定义为表面灭菌后叶片中的所有真菌物种；以下简称“ FF”）对于寄主植物的生长和健康至关重要，并且也可能影响生态系统的功能。尽管有这种重要性，但很少有研究明确检查宿主过滤在塑造当地FF群落中的作用，并且我们对有症状（由真菌病原体引起）和无症状叶片之间的FF群落组装的差异了解甚少，并且之间是否存在系统发育一致性。寄主植物和FF。我们使用ITS1基因生物标记的MiSeq测序方法，对青藏高原高寒草甸25种寄主植物物种（分别为有症状和无症状的叶子）的FF群落进行了研究。我们基于系统发生分析评估了FF与植物相互作用的系统发生一致性，并研究了FF群落的α和β系统发育多样性指数。我们发现无症状和有症状叶子对寄主植物和FF的系统发育一致性的强烈支持，并且由寄主引起的过滤器似乎在塑造FF群落中起主要作用。最重要的是，我们提供了独立的证据证明宿主环境过滤（由真菌感染引起）在驱动有症状叶子中的FF群落组装方面胜过竞争排斥。我们的结果通过证明宿主环境过滤在推动FF社区集会中的重要性，有助于加强FF社区集会的基础。并且由宿主引起的过滤器似乎在塑造FF社区方面起着重要作用。最重要的是，我们提供了独立的证据证明宿主环境过滤（由真菌感染引起）在驱动有症状叶子中的FF群落组装方面胜过竞争排斥。我们的结果通过证明宿主环境过滤在推动FF社区集会中的重要性，有助于加强FF社区集会的基础。并且由宿主引起的过滤器似乎在塑造FF社区方面起着重要作用。最重要的是，我们提供了独立的证据证明宿主环境过滤（由真菌感染引起）在驱动有症状叶子中的FF群落组装方面胜过竞争排斥。我们的结果通过证明宿主环境过滤在推动FF社区集会中的重要性，有助于加强FF社区集会的基础。