Do pollen and oil-collecting bees differ on pollination performance? The case of three oil-producing Iridaceae species in Brazilian Pampa

Premise Oil-producing flowers from distinct species could depend in different extent on pollination by oil bees and pollen bees that could also act as pollinators in some populations. The specialization-generalization continuum in pollination systems of oil-producing Iridaceae as already described. Therefore, the goal of this study was to investigate the performance of oil and pollen bees as pollinators of three oil-producing species of Iridaceae: Cypella herbertii, Kelissa brasiliensis and Herbertia pulchella. Methods The species varies in morphological traits, elaiophores position and visitation rates of two distinct bee functional groups. Oil bees are considered thieves when collecting oil in two of the three species studied. We combined data from visitation frequency and pollen deposition on stigmas to test the role of each functional group of bees as effective pollinators. Results Oil bees performed better as pollinators of C. herbertii; Pollen and oil bees are equally important in pollination of K. brasiliensis and Pollen bees performed slightly better as H. pulchella pollinators. In addition, oil seems to play an important role in attraction of oil bees to K. brasiliensis and H. pulchella flowers and the opportunistic behavior of oil bees made them functionally act as effective pollen-collecting bees in these two plant species. Conclusions These finds reinforce that specialization of oil pollination systems is a continuum and other functional groups of bees could act synergically in the pollination of oil-producing flowers.