ITS pre-processing and OTU picking was carried out with mothur 1.35.1 . Sequences were subsampled in mothur to 60,000 reads per sample, with distances generated using USEARCH . Chimeras were eliminated using the UCHIME algorithm . The similarity threshold for ITS sequences belonging to the same operational taxonomic unit (OTU) was set to 97% and clustered by CD-HIT-EST  with cluster representative sequences selected based on abundance. Taxonomic classification of OTUs was performed against the UNITE v6 database  with species assigned at 97% identity threshold. Samples were normalised to 28,090, the lowest number of reads per sample for downstream analysis by Quantitative Insights into Microbial Ecology 1.9.0 (QIIME) . Alpha diversity was measured using parallel_alpha_diversity.py script using observed_species and Chao1 metrics. An OTU network was generated using the make_OTU_network.py script. The resulting network was visualized in Cytoscape (3.5.1) using a spring-embedded layout.