High diversity of basal fungal lineages and stochastic processes controlled fungal community assembly in mangrove sediments.

Abstract

Fungi are key components of microbial community in mangrove wetlands, with important roles in the transformation of nutrients and energy. However, existing studies typically focus on cultivable fungi, and seldomly on the structure and driving factors of the entire fungal communities. The compositions, community assembly and interaction patterns of mangrove fungal community on large scale remain elusive. Here, biogeography, assembly and co-occurrence patterns of fungal communities in mangrove across Eastern to Southern China were systematically analyzed by targeting the entire ITS region with high-throughput Pacific Biosciences single-molecule real-time sequencing. The analysis recovered a high level of fungal diversity, including a number of basal fungal lineages not previously reported in mangroves, such as Rozellomycota and Chytridiomycota. Beta nearest-taxon index analyses suggested a determinant role of dispersal limitation on fungal community in overall and most individual mangroves, with supporting from the strong distance-decay patterns of community similarity. Further, nonmetric multidimensional scaling analyses revealed a similar biogeography of dominant and rare fungal community. A minor role of environmental selection on the fungal community was noted, with geographical location and sediment depth as crucial factors driving the distribution of both, the dominant and rare taxa. Finally, network analysis revealed high modularized co-occurrence patterns of fungal community in mangrove sediments, and the keystone taxa might play important roles in microbial interactions and ecological functions. The investigation expands our understanding of biogeography, assembly patterns, driving factors, and co-occurrence relationships of mangrove fungi, and will spur the further functional exploration and protection of fungal resources in mangrove. IMPORTANCE As key components of microbial community in mangroves, fungi have important ecological functions. However, fungal community in mangrove on large scale is generally elusive, and mangroves are declining rapidly due to climate change and anthropogenic activities. This work provided an overview of fungal community structure and biogeography in mangrove wetlands along an over-9000 km coastline across Eastern to Southern China. Our study observed a high number of basal fungal lineages in mangrove sediments, such as Rozellomycota and Chytridiomycota. In addition, our results highlighted a crucial role of dispersal limitation and a minor role of environmental selections on fungal community in mangrove sediments. These novel findings add important knowledge about the structure, assembly processes, and driving factors of fungal community in mangrove sediments.