BayCEER Workshop 2025

Effects of altitudinal variation in lichen-associated microbial communities

P 1 in Posters

The lichen symbiosis is one of the most successful and ecologically significant interspecies interactions, having evolved independently multiple times throughout the evolutionary history of higher fungi. The primary symbiotic interaction takes place between the fungal partner and its associated photobiont, typically a green alga. However, the lichen microbiome is much more complex. The diversity and community assembly of the endolichenic microbiome responds to environmental changes (e.g. temperature, moisture). These factors naturally covary with elevation, therefore allowing us to study the effects that come with it using a space-for-time substitution. We expected that higher humidity levels favour a higher microbial α-diversity, especially a higher abundancy of the desiccation-susceptible photobionts.

Lichen thalli of two species (Cladonia digitata & Hypogymnia physodes; n= 15 each) were sampled along an elevation gradient of 371 m in the Franconian Fichtel Mountains and processed for Amplicon Sequencing.

The data revealed that the fungal and algal community is more diverse at higher elevation plots in both species. The bacterial diversity showed species specific reactions to altitude. In contrast to our expectations, the abundancy of photobiontic Viridiplantae did not react to altitude. However, there was a significant increase in the ratio of Chloroplasts per photobiont with rising elevation levels in Cladonia. This suggests that Cladonia mediates higher photosynthesis rates at higher elevations by adjusting the abundancy of chloroplasts within the photobionts, not the photobionts themselves. In this setup, the fungal and algal communities were richer in moister and colder settings, highlighting the importance of climate change management for maintaining diverse fungal communities. Overall, the results demonstrated that endolichenic microbial communities serve as effective indicators for environmental change, but  the responses are mostly species-specific.

Keywords: Lichen microbiome Elevation gradient Photobiont responses Diversity patterns