Variation in floral morphology within a population of Aster hispidus var. tubulosus ( A steraceae, A stereae)

The family A steraceae has a particular inflorescence, the capitulum, consisting of ray florets and disc florets. The ray florets function as petals that attract pollinators. Marked variation in the ray floret morphology is known in a natural population of Aster hispidus var. tubulosu s ( A steraceae). We analyzed the variation and found two distinct types in the ray florets, the long tubular ray floret and the ligulate ray floret. In this species, therefore, the variation in floral morphology among capitula, each of which is the basic pollination unit, is caused by the variation in the composition of the two ray floret types among capitula. We evaluated the sources of the observed variation in the floral morphology among capitula within a population using a hierarchical analysis that separated within‐individual (i.e. among capitula within each individual) and between‐individual components of the variation. We found that the main source of the variation lay at the between‐individual level, not at the between‐capitulum level nested within individuals. This finding will provide the basic knowledge that enables future study exploring whether the between‐individual variation in floral morphology caused by the compositional variation of the ray floret types leads to differential pollination success of individual plants in species of A steraceae.