Nestedness in Arbuscular Mycorrhizal Fungal Communities in a Volcanic Ecosystem: Selection of Disturbance-tolerant Fungi along an Elevation Gradient

Abstract

Arbuscular mycorrhizal (AM) fungi play a significant role in the establishment and resilience of vegetation in harsh environments, such as volcanic slopes, in which soil is frequently disturbed by ash falling and erosion. We characterized AM fungal communities associated with a pioneer grass in a volcanic slope based on the disturbance tolerance of the fungi, addressing the hypothesis that soil disturbance is a major ecological filter for AM fungi in volcanic ecosystems and, thus, fungi that are more tolerant to soil disturbance are selected at higher elevations (i.e. nearer to the crater). Paired soil-core samples were collected from the rhizosphere of Miscanthus sinensis between the vegetation limit and forest limit on a volcanic slope and used in a trap culture with M. sinensis seedlings, in which one of the paired samples was sieved to destroy hyphal networks (disturbance treatment), while the other was not (intact treatment). Seedlings were grown in a greenhouse for two months, and the roots were subjected to molecular analysis of fungal communities. AM fungal diversity decreased with increasing elevations, in which nested structure was observed. Community dissimilarity between the disturbed and intact communities decreased with increasing elevations, suggesting that communities at higher elevations were more robust against soil disturbance. These results suggest that AM fungi that are more tolerant to soil disturbance are more widely distributed across the ecosystem, that is, they are generalists. The wide distribution of disturbance-tolerant fungi may have significant implications for the rapid resilience of vegetation after disturbance in the ecosystem.