Ericaceous plant-fungus network in a harsh alpine-subalpine environment

In terrestrial ecosystems, plant species and diverse root-associated fungi form complex networks of host-symbiont associations. Recent studies have revealed that structures of those below-ground plant-fungus networks differ between arbuscular mycorrhizal and ectomycorrhizal symbioses. Nonetheless, we still remain ignorant of how ericaceous plant species, which dominate arctic and alpine tundra, constitute networks with their root-associated fungi. Based on a high-throughput DNA sequencing dataset, we characterized the statistical properties of a network involving 16 ericaceous plant species and more than 500 fungal taxa in the alpine-subalpine region of on Mt. Tateyama, central Japan. While all the 16 ericaceous species were associated mainly with fungi in the order Helotiales, they varied remarkably in associations with fungi in other orders such as Sebacinales, Atheliales, Agaricales, Russulales, and Thelephorales. The ericaceous plant-fungus network was characterized by high symbiont or host preferences. Moreover, the network had a characteristic structure called "anti-nestedness", which has been previously reported in ectomycorrhizal plant-fungus networks. The results lead to the hypothesis that ericaceous plants in cold environments can host unexpectedly diverse root-associated fungal taxa, constituting networks whose structures are similar to previously reported ectomycorrhizal networks but not to arbuscular mycorrhizal ones.