Restricted gene flow between two alleged subspecies of Albinaria cretensis(Gastropoda, Pulmonata, Clausiliidae)

Two morphologically similar forms of pulmonate snails of the Albinaria cret ensis complex, Albinaria cretensis cf: vexans and Albinaria cretensis sphak iota, with ribbed and relatively smooth shells, respectively, occur sympatr ically but with a mosaic distributional pattern in the Imbros gorge (Crete, Greece). These forms were studied conchologically and using allozyme analy ses and RAPD to investigate their genetic and phylogenetic relationships. G ene flow between the two forms is minimal. Genetic similarity between morph ologically similar forms collected at different places in the gorge is larg er than between distinguishable forms found at the same locality. Hybrids a re formed only incidentally. There are neither sharp borderlines nor hybrid zones between the two forms. In a gorge c. 10 km to the west, a relatively smooth form is found together with Albinaria cretensis tenuicostata and Al binaria sublamellosa heteroptyx, both characterized by ribbed shells. Using the same methods, it turned out that the form with smooth shells is geneti cally almost identical to the conchologically indistinguishable one from th e Imbros gorge, and different from the local A. cretensis tenuicostata. The se data support the view that A. c. sphakiota is a separate species occurri ng in both gorges. The fact that A. sublamellosa clusters among A. c. sphak iota, does not allow for any conclusions because the analyses were not desi gned for an investigation including that species. The results are in favour of the view hitherto based on shell morphology mainly, that there are many genetically more or less isolated entities, sometimes with very restricted ranges, within the genus Albinaria.