Abstract

Macrofungi are essential components of ecosystems. Due to the ephemeral nature of sporocarps and their complex life histories, determining macrofungal diversity and distribution can be challenging. Without sampling all the different compartments (e.g., soil, plants, air) where fungi can be found, it is impossible to determine whether a fungus is absent from an area or is present, but not sexually reproducing. We used a hierarchical sampling approach at eight long-term plots distributed across continental USA. We sampled in three habitat types (oak woodland, Pinaceae forest, grassland) and two fire regimes (burned, unburned). We collected eDNA from soil, litter, plant roots, seeds, leaves, air and sampled sporocarps. Environmental variables were recorded. We used ITS2 amplicon sequencing and performed PERMANOVA and GLMM to assess composition across sites. Results from soil and leaf litter reveal that fungal community structure is primarily driven by ecoregion and secondarily by sampling compartment and habitat. Species richness is driven by the combined effect of ecoregion and sampling compartment, and to a lesser extent by the combined effect of sampling compartment and habitat. While the ecoregion was an important driver of species richness for fungal orders, fire had a more variable effect. Notably, soil Agaricales tended to be richer in the Taiga whereas leaf litter Agaricales were richer in the Great Lakes region. Similarly, soil Russulales were richer in the southeast while leaf litter Russulales were richer in the northeast. These results suggest that fungal orders have distinct geographical patterns depending on the sampling compartment they are in.