A Comparative Study On The Fungal Communities Associated With Two Variants Of Lobaria Retigera

According to recent studies, lichen symbiosis system mainly includes four components, mycobionts, photobionts, non-photoautotrophic bacteria and endolichenic fungi. Mycobionts support and control the symbiosis system, provides a habitat for others; photobionts provide carbon/ nitrogen resource; non-photoautotrophic bacteria play a role as nitrogen resource supplement. Although it has been demonstrated that endophytic fungi are benifite to hosts' survival competition, but until nowadays, the function of endolichenic fungi is still undefined.Lobaria retigera var. retigera(Lrr) and Lobaria retigera var. subisidiosa(Lrs), two variants of L. retigera, have similar morphologic features and habitat but contain different secondary metabolites. Lrr contains only small amounts of terpenoid compounds, Lrs contains norstictic acid and stictic acid in addition to large number of terpenoids.,and all of these secondary metabolites have antifungal activity. The comparative study of the endolichenic fungal communities between Lrr and Lrs will clarify the influence of lichen secondary metabolites on endolichenic fungal communities, and reveal the role of endolichenic fungi in the lichen symbiosis system.In view of culture method can only get a small amount of endophytic fungi, in this research, high-throughput sequencing technology was first used to compare the endolichenic fungal communities between Lrr and Lrs, which have same origin, habitat, substrate, and collecting time. The relative abundance between mycobionts and endolichenic fungi showed that the biomass of endolichenic fungi in Lrr was much higher than Lrs. The trend and quantity OTU decay curve indicated that the species diversity of endolichenic fungi in Lrr is much more than Lrs. The cluster analysis revealed that host specificity of endolichenic fungi was definitely existed in both Lrr and Lrs. Taxonomy analysis presented that Lrs harbored more Basidomycota fungi than Lrr; Ascomycota fungi, which have more toleration for lichen secondary metabolites, had high abundance in Lrs than Lrr; At order level, Lrs harbored more specific species than Lrr. Host origin, habitat, substance, collecting time, host's taxonomy and lichen secondary metabolites contained in host may affect the endolichenic fungi communities. Lrs and Lss have same origin, habitat, substance, collecting time and similar taxonomy relationship, this research indicated that lichen secondary metabolites is the main factor. The antifungal activity metabolites in Lrs can explain the results, mycobionts can restrain the overgrowrth, the biomass and the species diversity of endolichenic fungi by producting antifungal activity metabolites. It will create a special ecology niche which is benefit to some special fungi groups. Therefore, in the lichen symbiosis system, mycobionts and endolichenic fungi may have competitive relationship.This research also showed that endophytic fungi, fungi and fungi parasitize on lichen thallus will also influence the endolichenic fungal communities. Through lichen secondary metabolites can affect the endolichenic fungi, the community heterogeneity will not much chance. Ascomycota fungi are major constituent in endolichenic fungal communities as well as a small quantity of Basidomycota fungi and fewer Zygomycota fungi, which is corresponding to previous cultrue-dependingresearches.