Unexpected High Diversity of the Mycobiota Associated With the Endemic Fern (Mankyua chejuense) in the Republic of Korea

Fungi-plant interactions have a long history starting with the evolution of land plants. Diverse fungi live with plants and influence on their ecology and physiology. Ferns are early diverging vascular plants and known to have fungal interactions especially with arbuscular mycorrhizal fungi. Compared to other land plants, however, diversity of non-mycorrhizal or endophytic fungi are rarely studied from ferns. Moreover, most studies are performed using microscopy or culture-dependent method, which suggests that the underestimation of fungal diversity associated with ferns. In this study, we investigated the mycobiota within roots and sporophore of fern focusing on Korean endemic and endangered species Mankyua chejuense using a metabarcoding approach. Also, the richness and community structure were compared between sampling sites and substrates (soil, root, and sporophore). A high diversity of the mycobiota was detected and was much higher than it previously reported. Fungal richness was significantly different between substrates. Community composition was also significantly different between sampling sites and substrates. Various fungal guilds were detected in root and sporophore such as arbuscular mycorrhizal fungi, dark septate endophytes, and saprophytes or potential pathogens. Indicator species of each substrate showed that fern-associated fungi have similar ecological characteristics with fungal species found from other land plants. Our results suggest that the mycobiota associated with ferns are diverse and they may influence the ecophysiology of ferns, thus understanding fungal diversity in ferns is important in fern biology.