Beetle Pollination of Magnolia praecocissima var. borealis(Reproductive Biology)

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The floral biology and pollination of Magnolia praecocissima var. borealis, a tall tree blooming before leafemergence in early spring, were studied in Hokkaido, northern Japan. The flower is protogynous, and each flower lasts about 9 days without closing its petals. The mean duration of the female-stage and the male-stage flowers is about 4 and 4-5 days, respectively. The flowering period of an individual tree can be divided into three sexual phases : female, bisexual, and male. Manual pollination and bagging experiments showed that the plants were selfcompatible and that pollinators were necessary for a flower to produce seeds. It was observed that several species of small pollen-foraging beetles were the most effective pollinators. The male-stage flowers offered pollen as a reward, while the female-stage flowers offered no reward ; it is likely that the non-rewarding female-stage flowers mimic the rewarding male-stage flowers. The pollination syndrome of Magnolia praecocissima var. borealis differs from North American Magnolia species in its long-lasting flowers, is no closure of flowers at night, and in lack of food in the female phase.
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