ALLOZYME COMPARISON OF 4 LITTORINID SPECIES MORPHOLOGICALLY SIMILAR TO LITTORINA-SITKANA

Eight species of the genus Littorina were hitherto recognised in the n orth-western region of the Pacific Ocean: L. sitkana, L. brevicula, L. mandshurica, L. squalida, L. aleutica, L. naticoides, L. kasatka and L. subrotundata. Using allozyme electrophoresis it has been demonstrat ed that, in the Kurile Islands, three of these species (L. sitkana, L. subrotundata and L. kasarka) co-occur, together with a fourth, still undescribed species (L. sp.). These four species were compared at 16 l oci coding for 13 enzymes. All species were easily distinguished by di agnostic enzyme markers. The mean genetic distances and ranges between species pairs are: L. sitkana and L. sp. D=0.622 (0.561-0.741), L. si tkana and L, subrotundata D=0.981 (0.821-1.110), L. subrotundata and L . sp. D=0.975 (0.955-0.995). The genetic distance between L. kasatka a nd each of the other three species was greater than 1 (range 1.123-2.0 87). These data suggest that L. sitkana, L. subrotundata and L. sp cou ld be members of a species complex; according to current classificatio ns these three belong to the subgenus Neritrema. However, the genetic distance between L. kasatka and L. sitkana is much greater than betwee n L. sitkana and other Neritrema species, and thus supports the classi fication of L. kasatka in the subgenus Littorina.