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Precise Sternotribic Pollination by Settling Moths in Adenophora maximowicziana (Campanulaceae)

Premise of research. The majority of lepidopteran-pollinated flowers deposit pollen on the faces and proboscises of the pollinators. However, studies suggest that some flowers are sternotribically pollinated by settling moths. The present study focused on the pollination system and pollen placement pattern of Adenophora maximowicziana, which has pendant, bell-shaped flowers with exserted styles.

Methodology. Diurnal and nocturnal flower visitors and their relative contributions to seed set of A. maximowicziana were compared in southwestern Japan. The pollen placement pattern of flower visitors, timing of anthesis, timing of sexual phase change, and diel pattern of nectar production were investigated to reveal floral adaptations to pollinators.

Pivotal results. Pollination experiments and pollen load analysis indicated that nocturnal noctuid moths are the most important pollinators. Pollen placement on noctuid moths is highly precise. The majority of pollen grains are deposited onto the ventral side of the latter thorax and former abdomen. The flowers are adapted to nocturnal pollinators; anthesis, change to pistillate phase, and nectar production by flowers exclusively occur at night.

Conclusions. This study confirms highly precise sternotribic pollination by settling moths in A. maximowicziana. Sternotribic pollination of A. maximowicziana by settling moths may be facilitated by the flowers’ pendant corollas with exserted styles.