Ecological science aims for general principles that are transferable, predictive and widely applicable across different local situations. However, natural history, in contrast to ecology, is rife with examples of the particular. In this study, we reject the validity of the general expectation that diversity hot-spots contribute to overall species diversity accordingly to their species richness. In eleven 1-hectare forest plots in four distinct areas across Great Britain, we recorded 550 epiphytic and epixylic lichen species, i.e. 73 % of the presently known British epiphytic flora. Species richness per site was regionally stratified and mirrored by functional diversity, but species composition differed among sites, and was unrelated to the distance between sites. Rare species and species restricted to a single site consistently represented a high proportion of the local species richness. This demonstrated that each site contributed substantially and evenly to the regional and national biodiversity of epiphytic lichens in Britain. Several functional attributes are quite specific to rare species, so further disappearance of rare species would lead to disproportionately high loss of overall functional diversity.