Synergistic interactions between an exotic honeybee and an exotic weed: pollination of Lantana camara in Australia

Lantana camara, a woody shrub originating in south and central America, is among the most widespread and troublesome exotic weeds of the old-world tropics. It invades pasture, crops and native ecosystems, causing substantial economic losses and environmental degradation. In Australia alone, L. camara is currently estimated to cover c. 40 000 km2. In glasshouse studies we demonstrate that L. camara requires cross-pollination to set fruit, and that honeybee visits result in effective pollination. Field studies carried out in Queensland, Australia, suggest that fruit set is limited by pollinator abundance, and that the main pollinator of L. camara throughout a substantial portion of its Australian range appears to be the honeybee, Apis mellifera. Seed set was strongly correlated with honeybee abundance, and at many sites, particularly in southern Queensland, honeybees were the only recorded flower visitors. Of 63 sites that were visited, seed set was highest at five sites where only honeybees were present. Hives are frequently stationed within and adjacent to areas such as National Parks that are threatened by this noxious weed. Management of honeybee populations may provide a powerful tool for cost-effective control of L. camara that has previously been overlooked. We suggest that there are probably many other weeds, both in Australia and elsewhere, that benefit from honeybee pollination.