Dispersal limitation may drive the structure of fungal microbiota of plant roots at small spatial scales. Fungal root microorganisms disperse through the plant rooting systems from hosts to hosts. Due to a pronounced host-preference effect, the composition of endophytic root microbiota may follow plant distribution. A given plant community may hence include a matrix of host-plant species that represent various habitat permeabilities to fungal dispersal in the floristic landscape. We experimentally tested the effect of host-plant isolation on endophytic fungal assemblages (Ascomycota, Basidiomycota, Glomeromycotina) inhabiting Brachypodium pinnatum roots. We calculated host-plant isolation using Euclidean distance (distance-based dispersal limitation) and Resistance distance (functional-based dispersal limitation), based on host presences. All fungal groups were more influenced by the resistance distance between B. pinnatum than by the Euclidean distance. Fungal dispersal was hence strongly related to the spatial distribution of the host-plants. The fungal groups displayed however different responses (in richness, abundance, and composition) to host isolation. Additionally, fungal assemblages were more strongly controlled by the degree of connectivity between host-plants during the prior year than by current connectivity. This discrepancy may be due to changes in plant species coverage in a year and/or to the delay of dispersal response of fungi. This study it the first to demonstrate how small-scale host-plant distributions mediate connectivity in microorganisms. The consequences of plant distributions for the permeability of the floristic landscape to fungi dispersal appear to control fungal assemblages, but with possibly different mechanisms for the different fungal groups.

中文翻译：

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寄主植物连接对羽状短柄草根系微生物群中真菌组合的影响

扩散限制可能会在小空间尺度上驱动植物根部真菌微生物群的结构。真菌根系微生物通过植物生根系统从宿主分散到宿主。由于明显的宿主偏好效应，内生根微生物群的组成可能遵循植物分布。因此，给定的植物群落可能包括寄主植物物种矩阵，这些物种代表植物区系景观中真菌传播的各种栖息地渗透性。我们通过实验测试了寄主植物分离对栖息在羽状短柄草根部的内生真菌组合（子囊菌门、担子菌门、球囊菌门）的影响。我们使用欧几里德距离（基于距离的扩散限制）和抗性距离（基于功能的扩散限制），基于宿主的存在来计算寄主植物隔离。所有真菌组受 B. pinnatum 之间的抗性距离的影响比受欧几里德距离的影响更大。因此，真菌的传播与寄主植物的空间分布密切相关。然而，真菌群对宿主隔离表现出不同的反应（丰富度、丰度和组成）。此外，与当前的连通性相比，真菌组合在前一年受寄主植物之间的连通性程度的控制更强。这种差异可能是由于一年中植物物种覆盖率的变化和/或真菌扩散反应的延迟。这项研究首次证明了小规模宿主 - 植物分布如何介导微生物的连通性。