Reproductive biology of Bredia hirsuta var. rotundifolia in Douliu.

圓葉布勒德藤是台灣特有變種植物，分布於臺灣中、南部低海拔山區，零星且稀少。本論文研究斗六地區圓葉布勒德藤的授粉者、物候、及花藥、花粉於授粉作用中的功能，探討其生殖生物學。期望提供保育計畫之參考，並藉此材料探討無花蜜且二型雄蕊花的授粉策略。物候調查結果可見，圓葉布勒德藤在斗六地區的花季始於九月初，於隔年一月結束。三個樣區中，黃杞林溪樣區為高光量、低濕度、植株為地生型，開花、結果數量最多；其次為高光量、高濕度、地生型及岩附生型植株的出水口樣區；鐵橋坑溪樣區為低光量、高濕度、植株全為岩附生型，開花、結果數量最少。附生型植株的分枝數量顯著較地生型多。因此可以推測，圓葉布勒德藤最適合行有性生殖的環境為高光量的環境，而低光量及附生的生育地則多行無性生殖。圓葉布勒德藤在斗六地區的主要授粉者是無墊蜂屬的蜂類，偶見長足條蜂屬蜂類；授粉蜂以震動授粉的方式自花藥中取出花粉。雖然人工授粉試驗結果顯示圓葉布勒德藤不具有自交不親和性，但由於單一分枝同時開花數量少，且授粉蜂通常不連續拜訪同一朵花，而是在花間移動，因此植株的配對系統偏向異交或兼性異交，其實是由授粉者的行為所造成。此外本物種花的粉珠比為1445.66± 350.99，亦支持此結論。二型雄蕊對授粉蜂的影響不同：長型雄蕊的存在不影響授粉蜂的訪花率，但短型雄蕊的存在則顯著影響訪花率，推測短型雄蕊具有吸引授粉者的功能。而短型雄蕊花粉的直徑雖較長型雄蕊的花粉大，但是其數量較少，且具有活性比例較低，因此推測植株投資於短型雄蕊的資源較少。而人工授粉試驗證實，雖然二型雄蕊的花粉均具有結實能力，但果實回收率及種子飽滿率均為以長型雄蕊花粉處理者高於短型雄蕊，因此推測短型雄蕊花粉的主要功能是提供授粉者取食，作為訪花的報酬物；長型雄蕊花粉則是主要進行授粉的花粉。Bredia hirsuta var. rotundifolia is an endemic and rare species in central and southern Taiwan. It is distributed at middle and southern Taiwan. This study investigated the pollinator, phenology, and the function of the dimorphic anthers and pollen at Dou-liu to understand the biology of its reproduction and to provide some information for the conservation projects. Furthermore, this study would try to find the pollination strategy of the flowers without nectar but with dimorphic anthers. The phenology of B. hirsuta var. rotundifolia at Douliu showed that its flowering seasons were September to January. Among the three sites, the Haung-chi-lin brook was a high- light and low-humidity place with all the plants terrestrial, and bore the highest number of flowers and fruits; the site at the water outlet was a high-light and high-humidity place with the plants both terrestrial and rock-epiphytic; the site at Tie-chao-cen brook was low-light and high-humidity, with all the plants were rock-epiphytic, and bore the least flowers and fruits. Additionally the rock-epiphytic plants had more branches than the terrestrial ones. Therefore, it could be suggested that the high-light place was more suitable for the B. hirsuta var. rotudifolia to conduct sexual reproduction, while the place with low light where the plants were rock-epiphytic performed more asexual reproduction. The main pollinators of B. hirsuta var. rotudifolia at Dou-liu were Amegilla sp. and Elaphropoda sp. which was rarely found. The pollinators took out the pollen grains from the anthers by buzz-pollination. The result of artificial pollinations showed that there was no inbreeding incompatibility. Since there were few flowers at anthesis on a branch at the same time and the pollinators tended to visit among the flowers, the mating system of this species could be xenogamy or facultative xenogamy. In addition, the pollen-ovule ratio was 1445.66�350.99, supporting the deduction above. Dimorphic anthers had different influences on the pollinators. The long anthers did not affect the pollinators'' visiting the flowers, but the short ones did significantly. Therefore, the short anthers have the function to attract the pollinators. Although the pollen grains in the short anthers were larger than those in the long anthers, they were fewer and had lower proportion of viability, indicating that it put less investment in the pollen grains than the long anthers. The result of artificial pollinations showed that the pollen in the two types of anthers could be all viable for fruit-setting, but the percentages of both fruits and full seeds collected were significantly different between the two types of anthers. Therefore, it suggests that the main function of the pollen in the short anthers was to feed the pollinator, while the pollen in the long anthers was the one that actually pollinating.摘要 i Abstract ii 表目錄 vi 圖目錄 vii 第一章、 前言 1 一、 物候學與生育地環境調查 2 二、 授粉者調查 2 三、 環境因子與生殖特徵之關係 3 四、 生殖配對系統（Reproductive mating-system） 4 五、 二型雄蕊之授粉功能 6 六、 研究動機與目的 6 第二章、材料與方法 8 一、研究地點與樣區 8 二、材料 9 三、授粉蜂及授粉行為確認 9 四、授粉者攜帶花粉確認 9 五、花粉、胚珠數量及粉珠比計算 10 六、授粉蜂出沒時間 10 七、環境因子資料蒐集 10 1. 葉候調查 11 2. 花候調查 11 3. 果候調查 12 九、二型雄蕊存在對授粉蜂行為的影響 12 十、花粉活性染色 13 十一、人工授粉試驗 13 第三章、結果 16 一、授粉蜂確認及訪花行為觀察 16 二、電子顯微鏡確認授粉者攜帶花粉種類 20 三、花粉、胚珠數量及粉珠比計算 23 四、授粉蜂出沒時間 23 五、樣區間環境因子差異 24 六、物候、生殖特徵與環境因子間之關係 24 七、二型雄蕊存在對授粉蜂行為的影響 30 八、花粉活性染色結果 30 九、配對系統 32 第四章、討論 34 一、 授粉者與授粉者行為 34 二、 物候調查與適生生育地環境 34 三、 營養器官與生殖器官生長之關係 35 四、 二型雄蕊對授粉者行為的影響與不同雄蕊花粉的功能 36 五、 配對系統與粉珠比 37 六、 結論 38 第五章、引用文獻 40 第六章、附錄 4