Reevaluation of reproductive strategies and mating system of insect-pollinated plants from the viewpoint of pollen dispersal patterns

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To test the hypothesis that diverse floral structures and flowering patterns of animal-pollinated plants may have developed to enhance the reproductive success through male function, i.e. pollination process, we investigated the relationships between floral traits and pollinator mediated pollen flow, and the relationships between pollination efficiency and breeding system of insect-pollinated plants. The pollination experiment using artificial inflorescences under controlled conditions revealed that nectar distribution within inflorescences, inflorescence structure, and floral (and inflorescence) densities effectively influence the pollinator behavior, resulting in pollination efficiency of plants. Observation and manipulations of the pollination situation and breeding systems of various insect-pollinated species under natural conditions revealed that (1) floral color change can be a pollination strategy to reduce the geitonogamous pollination by controlling the number of successive flower visits within plants, (2) floral sex allocation of hermaphrodite flowers varies among flowers within inflorescences differently between populations depending on the type of pollinators having different pollination efficiencies, (3) variations in flowering phenology sometimes cause different pollination efficiency and genetic diversity of progenies due to the seasonal variations in pollinator activity, (4) bee-pollinated species may have higher spatiotemporal fluctuations in seed-set success than fly-pollinated species, because bees usually more susceptible to the climatic conditions than flies, and (5) clonal growth may decrease the outcrossing seed production due to acceleration of geitonogamous pollination among ramets within same genet, indicating a trade-off between clonal growth and sexual reproduction. These results indicate the importance of pollination process for reproductive success and population growth of insect-pollinated plants.