Maritime influence on lichen diversity was investigated in 19 stations, from sea level to 1600-1700 m alt., in a part of SW Italy stretching from the Tyrrhenian coast to the eastern slopes of the Apennines (Latium, Campania, and Molise regions). In each station, both common and rare species were recorded. 454 infrageneric taxa were found, three of which are new to Italy (Enterographa elaborata, Melaspilea ochrothalamia, and Phaeographis smithii). 143 species are new to Campania, 37 to Latium, and 29 to Molise. Cluster analysis, employed to detect groups of floristically similar stations, showed that the incidence of suboceanic species is a good marker for delimiting the borders of "Tyrhenian ltaly", a term which is critically discussed.
