Mate Choice in Molluscs of the Genus Littorina (Gastropoda: Littorinidae) from White Sea

We studied the reproductive behaviour associated with mate choice by size in three species of White Sea molluscs genus Littorina—L. saxatilis, L. obtusata and fabalis. Three behavioural patterns were revealed after a comparative analysis male snails. The males obtusata, regardless their size, could all females but preferred to larger ones. fabalis chose own or larger. saxatilis mated approximately size. In first case (L. obtusata), there is free exchange genes between groups population. second fabalis), gene transfer from small any large limited. third saxatilis), flow limited individuals dramatically different Thus, fabalis, varying degrees restriction random mating assortativity choosing partner was expressed, which under certain circumstances (divergence econiches, presence ecotypes differing lack stronger natural selection other direction) can favour sympatric speciation. periwinkles’ sexual found only obtusata. two species, no statistically significant differences copulating non-copulating females. This appears be due occurrence size-assortative these limits ability choose female partners.