Abstract
Epibiontic mollusc communities associated with Pinna nobilis L. in the Straits of Messina (Sicily, Italy) are described. Some relationships were found between species richness and diversity in respect to shell size. Progressive variations in community structure were found, demonstrating how epibiontic communities evolve towards a well-characterized biocoenosis. On the contrary, environmental and anthropogenic disturbances hinder this process, favouring an increase in species richness and Shannon-Wiener diversity.