High and balanced contribution of regional biodiversity hotspots to epiphytic and epixylic lichen species diversity in Great Britain

Abstract

We surveyed epiphytic and epixylic lichens in eleven 1-hectare forest plots located in representative old-forest stands in four distinct regions of Great Britain that are well-known centres of lichen biodiversity. We aimed to analyse the patterns of lichen biodiversity in these important biodiversity hotspots from a British perspective. In total, we recorded 550 lichen species in 11 ha, i.e. 73% of the presently known British epiphytic and epixylic lichen flora. Species richness per site was regionally stratified and varied from 126 to 235 species. Although the presence of frequent species coincided with total species richness in the respective hotspot, rare species (those with <50 records in Great Britain since 2000) were more balanced among hotspots and relatively independent of species richness. Species turnover contributed significantly and evenly to the species composition regardless of species richness so that hotspots did not have nested structure, typical for the hotspots in Central Europe. Although British hotspots generally shared more species within regions than between regions, geographic distances between regions did not correspond with the differences in species composition. The results document the importance and irreplaceability of the surveyed hotspots for lichen diversity in Great Britain, notwithstanding their current species richness and past depletion due to long-term acid deposition and habitat degradation.