Highly heterogeneous mycobiota shape fungal diversity in two globally distributed lichens

Lichens are multi-kingdom symbioses in which fungi, algae and bacteria interact todevelop a stable selection unit. In addition to the mycobiont forming the symbiosis,fungal communities associated with lichens represent the lichen mycobiota. Theirdiversity is still largely unknown, we therefore aim to characterize it in two cosmopolitanlichens, i.e., Rhizoplaca melanophthalma and Tephromela atra. The mycobiota wereinvestigated across a broad range of their distribution using both a culture-dependentapproach and environmental DNA metabarcoding. The variation of the mycobiotaassociated with the two lichen species is extremely high, and a stable species-specificcore mycobiota is hardly identifiable. Most of the mycobiota taxa are present in a lowfraction of the samples, and no taxon is ubiquitously present in either lichen species.The mycobiota are thus composed of heterogeneous fungi, and some taxa aredetectable only by the culture-dependent approach. We suspect that lichens act asniches in which these fungi may exploit the thallus resources, while only a few mayestablish more stable trophic relationships with the major symbiotic partners.