THE MAINTENANCE OF THE ANDRODIOECY : HOW DOES THE BREEDING SYSTEM AFFECT THE MALE REPRODUCTIVE SUCCESS IN THE CASE OF THE ANDRODIOECIOUS TREE, FRAXINUS SIEBOLDIANA BL. (OLEACEAE)?

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ANDRODIOECY IS VERY RARE BREEDING SYSTEM IN THE FLOWERING PLANTS. THE BREEDING SYSTEM AND POLLINATION BIOLOGY OF THE ANDRODIOECIOUS TREE, FRAXINUS SIBOLIDIANA WERE STUDIED BY THE OBSERVATION AND THE ELECTROPHORETIC ANALYSIS IN THE NATURAL POPULATION. THE RESULTS OF HAND-POLLINATION AND BAGGED EXPERIMENTS SHOWED THAT THE BREEDING SYSTEM OF THIS PLANT IS BOTH ANEMOPHILY AND ENTOMOPHILY. THE PERCENTAGES OF FRUIT-SET IN SELF-POLLINATION WAS LOWER THAN THAT IN THE OUT-CROSSING. THE FREQUENCY OF VISITATION OF POLLINATORS PER DAY WAS SIGNIFICANTLY HIGHER IN MALE PLANTS THAN THAT IN HERMAPHRODITIC PLANTS. THE OUTCROSSING RATIO ESTIMATED WAS EXTREMELY HIGH VALUE, 0.83. THE VALES OF INBREEDING COEFFICIENT WERE DIFFERENT BETWEEN SEXES IN FOUR LOCI EXAMINED. ESPECIALLY IN FEMALE PLANTS THE FREQUENCY OF HETEROZYGOTE WAS SIGNIFICANTLY APART FROM THE VALUE OF HARDY-WEINBERG EQUILIBRIUM. IN THE CONTRAST, IN THE MALE PLANTS IT WAS NOT SIGNIFICANTLY DIFFERENT FROM THAT OF HARDY-WEINBERG EQUILIBRIUM. THE POLLINATION SYSTEM, HIGH OUTCROSSING RATE AND HIGH INBREEDING DEPRESSION MIGHT PLAY IMPORTANT ROLE IN THE MAINTENANCE OF ANDRODIOECY IN THIS PLANT.