Patch size changes the composition of flower visitors and influences pollen flow

ABSTRACT Background The spatial structure and size of plant populations affect foraging choices of pollinators and, consequently, pollen transfer within and between populations. Aims To understand pollination patterns in relation to population size and pollinator selectivity we quantified patch size and pollen flow in natural populations of Richardia grandiflora, a neotropical perennial herb. Methods We assessed the composition of flower visitors, the number of flowers visited, and the frequency of visits in patches of different sizes. In addition, we measured the inter- and intra-patch-size pollen transfer (pollen from patches of different sizes and from the same patch/same patch size, respectively) using fluorescent dyes as pollen analogues. Results We recorded 22 species of insects, mainly bees, with Apis mellifera standing out as the major visitor in medium and large size patches. Large patches received a greater richness and abundance of flower visitors, had more flowers visited, and greater pollen flow overall (62%), representing 62% of the total intra-patch-size and 64% of inter-patch-size pollen flow. Alternatively, small patches represented 16% of the total intra-patch-size and 5% of the inter-patch-size pollen flow. Native bee species were found almost exclusively in small patches. Conclusion Small patches are important for sustaining rare floral visitors while large patches are more relevant for diverse pollination events.