Pollination effectiveness of European honeybee,Apis mellifera(Hymenoptera: Apidae), in an Oriental persimmon,Diospyros kaki(Ericales: Ebenaceae), orchard

Most common cultivars of Oriental (or Japanese) persimmon,Diospyros kakiThunb. (Ericales: Ebenaceae), set mostly female flowers and require pollen from male flowers of other cultivars for pollination. Growers often introduce the European honeybee,Apis melliferaL. (Hymenoptera: Apidae), into their orchards to promote pollination. Here, we investigated the pollination effectiveness ofA. melliferaforD. kaki'Saijo,' by monitoring flower visitors, analyzing pollen grains on bees' body surfaces, and comparing the number of mature seeds in fruits among years with different pollinator availabilities.Apis melliferaand the bumblebeeBombus ardens ardensSmith (Hymenoptera: Apidae) were the major visitors for 3 years, although their dominance varied among years. The number of mature seeds was positively correlated with the number ofB. ardens ardensvisitingD. kakiflowers, but not with that ofA. mellifera. Apis melliferamight be less efficient because visitors to female flowers carried significantly fewer pollen grains on their body surfaces than those ofB. ardens ardens. Analysis of pollen loads of honeybees captured at their nest entrance suggested their preference for red clover,Trifolium pratenseL. (Fabales: Fabaceae), andToxicodendronspp. (Sapindales: Anacardiaceae), overD. kakias a pollen source in our study site. The effectiveness ofA. melliferaonD. kakipollination should be carefully evaluated considering the effects of coexisting floral and pollinator species.