Daily partitioning of pollinators in an African Acacia community

Many studies have shown sympatric plants with similar floral structures to have flowering periods separated in time, and this is usually interpreted as a selective response to competition for pollination. In highly seasonal habitats, however, the time available for flowering may be highly constrained, and many species often flower together. Under such conditions, one alternative to temporal partitioning on a seasonal scale is for species to flower simultaneously, but with pollen release (dehiscence) structured on a diurnal timescale. Here we provide evidence for such diurnal partitioning of both floral resources and pollinator visitation in an African Acacia community. Temporal separation is enhanced by differences in the rewards offered by Acacia species to their pollinators:species producing nectar as well as pollen receive flower visits from insect groups absent from acacias offering only pollen. In contrast to competition for pollination, this situation may promote mutualistic maintenance of shared pollinators by the Acacia species.