Soil propagule banks of ectomycorrhizal fungi associated with above the treeline in the Siberian Arctic.

Microbial symbionts are essential for plant niche expansion into novel habitats. Dormant propagules of ectomycorrhizal (EM) fungi are thought to play an important role in seedling establishment in invasion fronts; however, propagule bank communities above the treeline are poorly understood in the Eurasian Arctic, where treelines are expected to advance under rapid climate change. To investigate the availability of EM fungal propagules, we collected 100 soil samples from Arctic tundra sites and applied bioassay experiments using as bait seedlings. We detected 11 EM fungal operational taxonomic units (OTUs) by obtaining entire ITS regions. was the most frequently observed OTU, followed by and OTU1. Three and one species were detected in the bioassay seedlings, indicating the availability of -specific suilloid spores at least 30 km from the contemporary treeline. Spores of . and . remained infective after preservation for 14 mo and heat treatment at 60 °C, implying the durability of the spores. Long-distance dispersal capability and spore resistance to adverse conditions may represent ecological strategies employed by suilloid fungi to quickly associate with emerging seedlings of compatible hosts in treeless habitats.