Dispersal-Dominated Yet Soil Variably Selected: Consistent Ecological Processes Underpin Spatial Distinction of...

Estuarine ecosystems exhibit strong environmental gradients and complex ecological processes. Here, we investigated the spatial patterns, ecological drivers and assembly processes of fungi across China's estuarine intertidal zones along a latitudinal gradient spanning the northern (NCS), eastern (ECS) and southern (SCS) coastal regions. The community α-diversity was higher in NCS and SCS than in ECS, whereas species richness was higher in ECS than in NCS and SCS. Community β-diversity increased significantly with geographic distance, with nitrate, organic carbon and ferric iron identified as the key environmental drivers. Niche analysis based on niche breadth (Levins' index) and species classification revealed a significant difference between the proportions of generalist species (32.92%) and specialist species (45.55%), and the mean niche breadth of fungal communities in NCS was significantly higher than that in ECS and SCS, reflecting the lowest environmental sensitivity. Neutral model analysis suggested that dispersal limitation was the predominant process shaping fungal community assembly, with its influence increasing from high- to low-latitude regions. Moreover, all fungal co-occurrence networks displayed weak modularity, highlighting a dispersed, non-modular interaction pattern among fungal taxa. These findings provide important insights into the macroecological patterns of intertidal fungal communities and their implications for ecosystem stability.