Factors shaping the lichen photobiome and mycobiome in a tropical lichen community

Lichen thalli host complex microbial communities, defined as a holobiont, which may foster the ecological stability and longevity of the lichen symbiosis. Currently, the understanding of the lichen features that structure the diversity of lichen holobionts in complex lichen communities in natural ecosystems remains incomplete. This study assessed the microbial community diversity and structure in taxonomically diverse co-occurring lichens associated with Trebouxiophyceae algae from Bolivian forests. We focused on three components of the lichen holobiont: the lichenized fungus (mycobiont), its associated algal (photobiome), and fungal (mycobiome) communities. We specifically tested the influence of mycobiont identity, lichen thallus morphological type, reproductive strategy, and secondary metabolites composition on the lichen-associated photobiome and mycobiome. To understand the specialization patterns between holobiont components, we investigated biotic interactions between the mycobiont and the lichen-associated photobiome and mycobiome using network analysis. We observed that co-occurring lichens host diverse, host-specific, yet overlapping photobiomes and mycobiomes. In particular, these microbial communities are influenced by the host's thallus morphological type and its secondary metabolite content. Finally, we demonstrated that both photobiome and mycobiome are shaped mainly by the mycobiont identity, which results in modular interaction networks, with strong phylogenetic signals and high levels of specialization.