DAILY PARTITIONING OF POLLINATORS IN AN AFRICAN ACACIA COMMUNITY

Many studies have shown sympatric plants with similar floral structure s to have flowering periods separated in time, and this is usually int erpreted as a selective response to competition for pollination. In hi ghly seasonal habitats, however, the time available for flowering may be highly constrained, and many species often flower together. Under s uch conditions, one alternative to temporal partitioning on a seasonal scale is for species to flower simultaneously, but with pollen releas e (dehiscence) structured on a diurnal timescale. Here we provide evid ence for such diurnal partitioning of both floral resources and pollin ator visitation in an African Acacia community. Temporal separation is enhanced by differences in the rewards offered by Acacia species to t heir pollinators:species producing nectar as well as pollen receive fl ower visits from insect groups absent from acacias offering only polle n. In contrast to competition for pollination, this situation may prom ote mutualistic maintenance of shared pollinators by the Acacia specie s.