Visitation of evening primrose by carpenter bees: Evidence of a 'mixed' pollination syndrome

Evening primrose, Oenothera elata, is generally considered a hawkmoth-pollinated plant species that exhibits several characteristics of a moth pollination syndrome. We re-examined its reproductive biology by testing the hypothesis that a twilight-foraging carpenter bee, Xylocopa tabaniformis orpifex, can serve as its pollinator. In our study population, pollen was deposited by carpenter bees on 56% of all the flower stigmas that were monitored during evening periods and at least 70% of those monitored during successive evening and morning periods; flowers that only carpenter bees were allowed to visit produced healthy seed pods about 3 weeks later. Given the effectiveness of X. tabaniformis as a pollinator and its overlap in range with Oenothera elata, we believe a mixed pollination syndrome that includes both bees and moths is a more appropriate characterization of the pollination biology of this plant species.