The High-Altitude Volcanic Caves of Mount Etna (Eastern Sicily): A Relevant Refuge for Some Ptero-Bryophyte Communities

A phytosociological analysis of the plant communities in high-altitude volcanic caves of Mount Etna (Sicily), based on literature data and unpublished relevés, is presented. A total of 147 phytosociological relevés were processed and analyzed using classification and ordination methods. Classification of the relevés, supported by ordination, showed two main vegetation groups: the first one includes communities of the Pohlion crudae alliance, and the other includes the vegetation from the Pohlio crudae–Asplenion septentrionalis alliance. Furthermore, two new communities, Pohlio crudae–Cystopteridetum dickieanae subass. amphidietosum mougeotii and Pohlio crudae–Cystopteridetum dickieanae subass. polystichetosum lonchitis, are proposed for Etna. The high-altitude caves can be considered a refuge for these ptero-bryophytic rare communities.