Rivers may constitute an overlooked avenue of dispersal for terrestrial fungi

While fungi are intimately associated with substrates in freshwater systems, the role of fungi in the open water column is less well defined. Using next generation sequencing of 0.2 μm–1 μm filtered water column samples, we detected abundant and diverse fungal sequences across 25 stream and river sites in the Ozark region of Oklahoma and Arkansas. Fungal communities were only weakly related to stream environmental metrics with the exception of total phosphorus (TP). We infer from our results that TP is acting as a proxy for unique catchment effects. We observed patterns of dominant community taxa at higher taxonomic groupings but lower taxonomic groupings were site specific. OTU functional assignment showed the majority of sequences to be related to plant and animal pathogens, and some saprotrophs. The likely allochthonous origin and strong site specificity of these fungi suggest overlooked dispersal via lotic waterways, which may have important biogeographic consequences for fungi.