Thanks to the Finnish GBIF node and their participation in the GBIF Metabarcoding Data Programme (MDT), the team behind the study successfully shared the full GSSP dataset as occurrences through GBIF, increasing discoverability and access for additional studies in airborne fungal DNA.
Infamously hard to sample and characterize, fungi are one of the most unexplored kingdoms of life, despite their diversity and ecological importance. While soil sampling has proven successful to some extent, patterns detected may be substrate-specific. A new approach involving capturing fungal spores from the air could pave the way for global fungal sampling.
In the Global Spore Sampling Project (GSSP), researchers installed so-called cyclone samplers at 47 locations in varying climatic zones and altitudes across all continents except Antarctica. Collecting all particles greater than one μm in size from the air, the units took two 24-hour samples per week for a least one year. Each sample contained particles filtered from 24 m3 of air.
For DNA sequencing of the more than 2,500 samples, the authors used PCR to amplify a specific region of the fungal genome, known as ITS2, a universal molecular barcode for fungi. From the sequences they derived amplicon variants which could be directly assigned to a known taxon or grouped into approximately species-level operational taxonomic units (OTUs). In total, the pipeline produced 27,954 species-level OTUs and 1,392 sequences that corresponded reliably to known species.
To validate the taxonomic classifications, they compared the distribution of species identified in study based on sampling locations with GBIF-mediated occurrence records. Overall, the distributions of the study data correlated significantly with GBIF occurrences with mismatches for only 1 per cent of species, suggesting valid taxonomic classifications.
Using a generalized linear model of the 485 most frequently occurring OTUs and climate data for the sampling locations, the authors found a strong ecological signal suggesting that most variation in species could be explained by differences in air temperature.