Arctic biocrusts highlight genetic variability in photosynthesis as a key driver of biodiversity

Background: Photosynthetic organisms, including cyanobacteria, algae, and bryophytes, are an essential part of biological soil crusts (biocrusts) in Arctic ecosystems. These organisms play key roles in supporting both the biocrusts themselves and associated plant communities by generating energy and nutrients under extreme environmental conditions. However, the genetic mechanisms underlying their adaptation to polar environments remain poorly understood. This study investigated the composition of phototrophic communities and their photosynthetic genetic capacity in Arctic biocrusts located at different elevations. Results: Metagenomic sequencing revealed that cyanobacterial communities exhibited no significant response to elevation, while this factor had a strong effect on the distribution of eukaryotic phototrophs. Increased elevation is typically associated with higher solar radiation, lower temperatures, and reduced water availability, all of which might increase environmental stress and influence the adaptation of photosynthetic organisms. In addition, photosynthetic gene profiling revealed a consistent dominance of photosystem II (PSII) genes across all sites, particularly psbB. In general, genes associated with photosystem I (PSI), chlorophyll biosynthesis, as well as the light-harvesting complexes of PSI and PSII, were significantly influenced by the increased elevation. Conclusions: The results expand our understanding of the functional role of phototrophic organisms in Arctic biocrusts. Furthermore, they highlight the importance of genetic photosynthetic capacity for resilience and adaptability under extreme environmental conditions, which may serve as a key factor in determining the composition of phototrophs in biocrusts.