Contribution of nocturnal moth pollination to buckwheat seed set

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Although diverse wild pollinators contribute to crop pollination, nocturnal pollinators have been largely overlooked. In this study, we focused on buckwheat, which relies on various insect species for pollination. Since buckwheat flowers are believed to close in the evening, earlier studies have exclusively examined the role of diurnal pollinators. However, some buckwheat flowers have been observed opening at night; thus, we can assume that nocturnal insects play a role in buckwheat pollination. Our field observations showed that 80% of buckwheat flowers that opened in the morning remained open at night. The insects visiting buckwheat flowers at night belonged to the moth families of Noctuidae, Crambidae, and Pyralidae. These moths were all found to have buckwheat pollen on their bodies. To quantify the contribution of nocturnal pollinators to seed set, we conducted a pollinator exclusion experiment using the following bagging treatments: no pollinators (bagging for 24 h), only diurnal pollinators (bagging from 18:00 to 06:00), only nocturnal pollinators (bagging from 06:00 to 18:00), and natural pollination (no bagging). The results showed that the seed set decreased in the following order: natural pollination, diurnal pollinators only, nocturnal pollinators only, and no pollinators, with one-fourth of the buckwheat seed sets resulting from nocturnal pollinators. However, the proportion of flowers open at night decreased as the flowering period progress, and the role of nocturnal pollinators appeared to decline over time. Our findings suggests that nocturnal pollinators may complementarily increase buckwheat seed sets, emphasizing the need to investigate overlooked nocturnal pollinators in crop pollination services.