Do introduced honeybees (Apis mellifera, Hymenoptera) provide full pollination service to bird-adapted Australian plants with small flowers?: An experimental study of Brachyloma ericoides (Epacridaceae)

In many previous studies of the effects of introduced honeybees on Australian ecosystems, it has been assumed that floral morphology is a primary factor determining whether introduced honeybees will be effective in pollinating endemic plants. Although both honeybees and birds contacted stigmas and anthers of the small-flowered Brachyloma ericoides (Epacridaceae), the exclusion of birds but not honeybees resulted in a significantly lower proportion of flowers producing capsules (12.3 +/- 2 vs 21.0 +/- 2%). This suggests that native birds contributed significantly to fruit set even though honeybees were much more frequent visitors to flowers (5-6 vs 0.7-2.5 times per day) and moved more frequently between plants (25 vs 12.2% of movements). Fruit set following exposure to birds and honeybees was very low compared with shrub species in general and may have been limited by the pre-emptive removal of pollen by the 10% of honeybees that actively collected pollen.