Drivers of fungal pathogen distribution in the soil and air of the U.S. Southwest are poorly understood. Fungal pathogen range may be determined by air dispersal limitations, environmental filtering, or both. Regional climate models predict more severe droughts along with less frequent, heavier rainstorms, which may encourage an increased amount of pathogenic spores, therefore, understanding mechanisms of fungal community assembly in soil and air is crucial. This study will determine the relative importance of dispersal limitation or environmental filtering on fungal communities as well as size pattern distribution of airborne spores.
120 soil samples and 60 air samples were taken along north-south and east-west transects, covering five states (CA, AZ, NM, NV, UT). Soil samples were taken in duplicate at 60 sites located away from major roadways. Simultaneously, air samples were taken using a BioImpactor sampler, which impinges spores onto an agar dish. Spore counts were performed on the air samples and classified by spore size (1-5, 5-10, 10-20, and 20-50 microns). DNA was extracted for sequencing using ITS2 region on the Illumina Mi-Seq platform to determine fungal community composition. Standard physical soil measurements were determined (pH, density, water content) for environmental analysis against abiotic factors involved in environmental filtering.
Results/Conclusions
Overall spore concentration significantly increased with mean annual precipitation (p=0.022). Moisture has been found to contribute to both spore production and spore longevity, leading to increased production and entrainment of airborne spores in areas with more precipitation. Spore distribution by size class was found to vary significantly with elevation (p=0.002), mean annual temperature (p=0.009), and longitude (p=0.005). The larger spores were more prevalent at higher elevations. Significant variation was found for all spore size classes except for the smallest (1-5 microns). The smallest spores remain suspended in the air longer and are likely able to be transported further distance, therefore, their concentrations are much more lower compared to spores 5 microns or larger which exhibit a point source type of distribution from the higher elevation areas.