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)?

无性繁殖是开花植物中非常罕见的育种系统。通过在自然种群中的观察和电泳谱分析，研究了白蜡树的繁殖系统和授粉生物学。人工授粉和套袋试验结果表明，该植物的育种系统兼具两性亲和性和胚性亲和性。自花授粉的坐果率低于异交。雄株每天访问传粉者的频率显著高于两性株。异交率估计值极高，为0.83。4个座位的近交系数在性别间存在差异。特别是在雌性植株中，杂合子的频率与Hardy-Weinberg平衡值有显着差异。相反，在雄株中，它与Hardy-Weinberg平衡没有显著差异。授粉系统、较高的异交率和较高的近交衰退率可能是维持该植物无性繁殖的重要因素。

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.