Is aerial dispersal an overlooked pathway for ectomycorrhizal truffle fungi?

The dispersal of ectomycorrhizal (EM) fungi is typically characterized by an ecological dichotomy in which aboveground (epigeous) mushrooms disperse via wind and belowground (hypogeous) truffles disperse via animal-mediated movement. To assess whether hypogeous EM fungi may be dispersed by wind more often than generally recognized, we used high-throughput sequencing of paired spore trap and soil samples at eight sites across the United States. Within the spore trap samples, hypogeous EM taxa represented 17.2 ± 1.62% (mean ± SE) of the total EM OTUs and 19.4 ± 1.75% of the total EM sequence reads. In general, their presence was characterized by episodic higher abundance events rather than continuous occupancy as compared to epigeous EM taxa. The hypogeous EM taxa found in spore traps also had significantly smaller average spore volumes than those remaining in the soil, likely facilitating their presence in air. Further, by identifying multiple instances of the same hypogeous EM OTU being present in spore trap and soil samples located tens of km apart, our study suggests wind may carry spores of hypogeous EM fungi considerable distances. Collectively, these findings indicate that the boundary between dispersal pathways for hypogeous EM fungi may be more fluid than previously thought and that specific traits and vectors allow them to exploit the atmosphere as a complementary dispersal pathway.