Unveiling lichen diversity on volcanic substrates: A comparative study across mainland Spain

Volcanic rocks harbor an interesting biota well-adapted to the stressful conditions imposed by the environment. Lichens species, with their remarkable resilience, are the most conspicuous organisms colonizing these ecosystems reflecting higher percentages of volcanic rocks coverage. This study provides a comprehensive analysis of lichen diversity across mainland Spain, focusing on the different locations of the volcanic zones and volcanism type, aiming to investigate differences in species richness, frequency, and functionality in four volcanic zones: central, northeastern, southeastern coastal, and southeastern inland. Fieldwork and literature review were used to compile a dataset of 360 lichen species from 85 localities. The results indicate that regional differences in species composition are driven by location of the volcanic zones. Functional traits such as growth forms, photobiont types, and secondary metabolites exhibit similarities across volcanic zones. At a local scale, differences in lichen composition appear influenced by the chemical composition of volcanic rocks. The findings underscore that despite high species turnover between volcanic zones, functionality remains consistent, with a clear dominance of species developing crustose thalli with green algal photobionts and secondary metabolites offering photoprotection in these harsh environments. This research helps fill the knowledge gap on lichen diversity in the Iberian Peninsula's volcanic regions. • Lichens are dominant organisms colonizing sun-exposed volcanic substrates. • Lichen species composition varies regionally across mainland Spain. • Local diversity is influenced by volcanic substrate chemistry. • Despite turnover, growth form and secondary metabolites remain stable across zones.