Phylogenetic and functional structure of lichen communities under contrasting environmental conditions

[Question] In order to identify the factors and assembly rules which potentially shape natural lichen communities we asked whether these communities are phylogenetically and functionally structured along an environmental gradient in beech forests in the Iberian Peninsula. [Location] A climatic gradient in the Iberian Peninsula. [Methods] We used species inventories, trait data and a molecular dated phylogeny to calculate phylogenetic and functional community metrics. We examined the phylogenetic and functional diversity of epiphytic lichen assemblages in nine beech forests along an environmental gradient. [Results] We found a significant pattern in the average phylogenetic and functional diversity across sites. Species at northern sites were less closely related than expected by chance (phylogenetic and functional overdispersion), suggesting that these communities could be structured by species interactions limiting the similarity among them (e.g. by competition and facilitation). In contrast, species occurring in the southern distributional limit of the host tree were phylogenetically and functionally clustered, implying that these communities could be primarily structured by environmental filtering, driven by the reduction of summer rainfall. Lower precipitation areas favoured fruticulose and squamulose species and a larger proportion of species with green algal photobionts and asexual reproduction. [Conclusions] Our results suggest that environmental filtering and species interactions regulate lichen communities differently under contrasting environmental conditions in beech forests in the Iberian Peninsula. These processes are reflected by the presence of key lichen traits that are phylogenetically conserved and can provide advantages for competition or adaptation to the environment.This research was supported by the Spanish Ministry of Education and Science (project BIOFRAG, CGL2007‐66066‐C04‐4/BOS), the Ministry of Science and Innovation (project EPICON, CGL2010‐22049) and the Ministry of Economy and Competitiveness (ECOMETAS, CGL2014‐53840‐REDT).Peer reviewe