Friend or foe? Impacts of the introduced tropical oil bee Centris nitida on a threatened and specialized native mutualism in Southern Florida

While we understand a great deal on the impacts of introduced generalist pollinators on the native ecosystems, very little is known about the impacts of naturalized specialist pollinators. The oil-collecting bee Centris nitida, which has recently naturalized in southern Florida, has been identified as a novel participant in an endemic specialized mutualism between Byrsonima lucida, a threatened native oil plant, and Centris errans, its sole native pollinator. In this study, we determined the impacts of this novel pollinator on B. lucida by assessing the degree of its pollen limitations in sites with and without the introduced oil bee, as well as in natural and garden settings. We also compared the key processes of pollination for both of the Centris bee species. The degrees of pollen limitation sustained by B. lucida were similar among sites with or without the introduced oil bee, and among natural or garden sites. The native oil bee's visitation rates (no. of visits/minute/flower) to B. lucida plants were not significantly reduced at sites where the introduced oil bees were present. The native oil bee had a lower foraging rate (no. of flowers visited/minute) and was a less efficient pollinator than the introduced oil bee. There has been no observed negative impact to either the native oil plant or bee, the introduced bee is absent in most natural areas, and it is also possible that the bee may arrive naturally given the trend in global warming. In light of these facts, we do not recommend any management action towards this introduced oil bee.