On the function of hermaphrodite florets in female inflorescences of Petasites japonicus (Asteraceae)

To examine the function of morphologically hermaphroditic, but functionally sterile, florets in female inflorescences of Petasites japonicus (Sieb. & Zucc.) Maxim., we conducted experiments in which all those florets were removed from female inflorescences. We hypothesize that those florets enhance female reproductive success by deceit, because they resemble the morphologically hermaphroditic, but functionally male florets, in male inflorescences. We found that the mean number of pollinator visits per inflorescence did not differ between the intact inflorescences and inflorescences in which such hermaphrodite florets had been removed. However, the mean duration of stay per visit to an inflorescence tended to be shorter in those with removed florets than in the intact inflorescences. The achene / female floret ratio was smaller in the inflorescences with removed florets than in the intact ones. We hence concluded that the hermaphrodite florets in female inflorescences enhance female reproductive success through prolonged duration of pollinator stay.