Cryptogam communities in Mediterranean coastal dunes as indicators of microhabitat effect and human influence

• Bryophytes and lichens are relevant but understudied in Mediterranean dunes. • They form defined communities influenced by different environmental factors. • A zonation of communities is not clear, and microhabitat factors are important. • At least two cryptogam communities are bioindicators of human disturbance. Mediterranean coastal dune morphology and dynamics are affected by a complex set of biotic and abiotic factors, from both natural and anthropogenic sources. These ecosystems are heavily degraded and endangered nowadays, making monitoring and management actions urgent. Despite their ecological relevance, bryophytes and lichens remain understudied in these ecosystems. This study aims to characterize the cryptogam communities in Balearic coastal dunes and evaluate their potential as bioindicators in Mediterranean dunes. A total of 335 relevés were conducted in 17 dune systems across the Balearic Islands. Plots were grouped in different cryptogam communities, which were characterized by their species composition and different environmental factors measured in the field. Plots could be grouped in a total of five cryptogam communities, which differed in species composition, richness and abundance, and in ecological preferences as indicated by the measured environmental variables. A zonation of communities was not clearly detected, and microsite variables seemed to play an important role. At least two of the cryptogam communities could be considered for monitoring dune system health. A community associated with Bryum dichotomum was related to ruderalization. A second community, characterized by the presence of Ptychostomum torquescens , could indicate an excessive stabilization of mobile dunes by human management. We propose cryptogam communities as bioindicators of Mediterranean coastal dunes health, which should be considered when planning monitoring and management actions.