Dioecious plants have male and female flowers on separate individuals. Among these plants, females and males often differ in flowering traits besides exist and development of stamen and gynoecium. The sexual dimorphism on inflorescence angle were reported in multiple species, but there is no report examined how the sexual dimorphism support reproductive success. In this study, we tested its effect to pollination efficiency and seed predation in Dioscorea tokoro.
A dioecious herbaceous climber, D. tokoro, has upright male inflorescences above the leaves and pendente female inflorescences under the leaves. The field experiment with artificial pollination suggested that females reduce reproduction success because of pollen limitation. We changed the angle of pendente female inflorescences to upright and tested the seed maturing and predation. The results suggested that the pendente female inflorescences limited pollination but could not avoid major seed predation by specialist insects. The pendente female inflorescences would have effects to avoid generalist insects but it is needed to examine under the condition with high pressure by generalist insects. In addition, we changed the angle of upright male inflorescences to pendente and tested the pollination efficiency. We will discuss the effects of the sexual dimorphism on inflorescence angle including these results.