Biological species-limits and systematics of the Clausiliidae (Gastropoda) of the Maltese Islands

Eight forms of Clausiliidae (Alopiini) are recognised from the Maltese archipelago and Lampedusa. Characters of their shells and distal genitalia are discussed. The distribution of all of the forms is essentially allopatric. Hybridisation usually occurs where ranges of different forms meet; in some cases hybrids are rare, but in others entire local populations are of hybrid origin. Based mainly on evidence of the extent of reproductive isolation, the seven forms in the Maltese Islands are classified into two biological species (syracusana and imitatrix). From evidence of their affinity it is suggested that these should be placed together in the genus Lampedusa, along with lopadusae from the Island of Lampedusa.