Variation in ectomycorrhizal fungal exploration types

Fungi are among the most diverse ecological communities with distinct roles in mediating terrestrial biogeochemical cycles. Plant associated mycorrhizal fungi provide vital nutrients to host plants, but their ecological strategies vary across guilds. Ectomycorrhizal fungi associate with >60% of trees on Earth, possessing distinct capacities for decomposition, nutrient uptake, and soil exploration due to variation in their niches and distributions. Recently, we demonstrated the ectomycorrhizal fungal composition is linked to continental scale forest productivity across Europe. Differences in ectomycorrhizal fungal exploration types based on the quantity and composition of emanating hyphae and associated traits help explain this connection. What factors define and shape the ecological strategy of ectomycorrhizal fungal exploration can provide fundamental insight into their differential roles in forests. To address this, we compared genomic variation and modeled species distribution patterns of ectomycorrhizal fungal taxa from different exploration types. The exploration type concept has received considerable scrutiny because it can vary within an individual species, has not been sufficiently investigated across a wide range of taxa, and local distributional patterns often vary across disparate studies. These are important short comings of the exploration type trait that I will discuss. Despite limitations, we observe clear signatures of fungal exploration type in fully sequenced fungal genomes and in species distribution patterns across Europe. Our results emphasize that biomass production volume and rhizomorph formation are important sub-traits of exploration types. We further demonstrate that exploration types often merged into single exploration categories should be separated to observe distinct distributional patterns. Our results also provide insight into which ectomycorrhizal fungal traits are associated with forest nitrogen and phosphorus limitations and in turn overall forest productivity.