Pilliga Ghosts: The Novel Fungi of the Rivers, Creeks, Lakes, and Dams of the Narrabri Region, Australia.

in size. ITS amplicon sequencing of water samples collected in November 2022 and June 2023 identified 344 OTUs, revealing clear temporal variation, with OTU richness significantly higher in November than in June. Notably, ~73% of sequences could not be reliably assigned to phyla, representing substantial 'fungal dark matter', although many of these sequences appear to have affinities with poorly characterised zoosporic fungi. Aquatic hyphomycetes were virtually absent. This observation may be due to regular filtering of conidia by hyporheic or ephemeral flow during the dry season in this region. Notably, this study reported the first Australian record of the ectomycorrhizal fungus, Laccaria miniata, detected in a mass fruiting event in June 2023. Furthermore, this study demonstrated that two sponges, previously undocumented in the region, are widespread, alongside a novel gastrotrich species occurring at most locations. Taken together, these findings reveal semi-arid freshwater systems in Australia are hotspots of unrecognised fungal and eukaryote diversity.