Aims Davidia involucrata is a rare and endangered plant endemic in China. Research has focused on its geographical distribution, morphological description, population ecology and synecology, introduction, reproduction, etc., but its developmental biology and pollination ecology have rarely been studied. Color has always been considered as an attraction to pollinators. Ecologists formerly studied the relationship between color and pollinator using filters and photography. Flavonoids are one of the most important pigments in flowers, and techniques for extracting and separating flavonoids have been developed; however, there have been no studies of the relationship between flavonoid variation and pollinators' visiting frequency. In this paper, we sought to determine whether flavonoids differ significantly and whether flavonoid variation affects pollination.

Methods We determined flavonoid composition in bracts, stamens and leaves. We also observed the visiting frequency of pollinators.

Important findings With floral development, the general flavonoid content of bracts, stamens and leaves all decreased. There were significant differences between each stage (p<0.001). The visiting frequency of Hymenoptera was high at the gynoecium stage, but no Coleoptera appeared. Flavonoids at the gynoecium stage may function in defense and inducement. Several flavonoid compounds increased and some others decreased, strengthening the contrast between flowers and leaves. It is likely that the contrast serves to attract pollinators.