Myco-, photobiont and bacterial microbiome associations along an elevational gradient in the Hohe Tauern, Salzburg, Austria

Lichens are among the few organisms capable of thriving in extreme environments, forming miniature ecosystems composed of diverse fungal, algal, and bacterial communities. To characterize their symbiotic community structure along climatic gradients, the composition, distribution, and interactions of their primary symbiotic partners (mycobiont [fungus]/ photobiont [algae]) and the bacterial microbiomes were studied. Using molecular techniques, including Sanger and high-throughput amplicon sequencing, we analyzed saxicolous lichens along an elevational gradient (1168–2562 m a.s.l.) in the Grossglockner region, Salzburg, Austria. The following research questions were addressed: (i) Do the symbiotic partners of lichens – mycobionts, photobionts, and bacterial communities – vary in composition and diversity along an elevational gradient? (ii) Do lichens at the same site share locally available symbiotic partners, such as photobionts, and bacterial microbiomes? All three partners of lichen communities, i.e. mycobionts, photobionts, and bacteria, varied in diversity and composition along the elevational gradient. Neighboring lichens within microhabitats shared photobionts, indicating local availability as a key factor in partner selection. However, bacterial microbiomes showed substantial heterogeneity across and within sites, influenced by mycobiont-photobiont interactions. The formation of local guilds drives new symbiotic combinations that may improve the adaptability of lichens to environmental changes and the colonization of new niches.