惠蓀林場牛奶榕與牛奶榕小蜂之共生研究

Abstract

本論文以臺灣中低海拔常見的牛奶榕(F. erecta var. beecheyana)與 牛奶榕授粉蜂(Blastophaga nipponica)為材料探討兩者的共生關係。牛奶 榕為雌雄異株的榕屬植物，產生種子和花粉、蟲癭的榕果分別在不同的植株。雌、雄 榕果在榕果外部形態相似，在榕果內部有明顯差異。雌榕果內小花總數平均約423.4 朵，分別是長花柱雌花約佔68.12%、中性花約佔31.88%，結實率約69.54%； 雄榕果內小花總數平均約1362.0，分別是短花柱雌花約69.58%、雄花約31.42%及極少 數的假兩性花，蟲癭率約37.15%。長、短花柱雌花除了在花柱長短有顯顯的差別外， 在柱頭形態、花柱形態、子房內胚珠形態構造有明顯差異，呈現雌花的 兩型性(dimorphology)。 中性花為雄蕊與雌蕊極為退化的兩性花；而雄花除了有雄蕊外，在雄蕊中央尚有極為 退化的雌蕊痕跡。雌、雄榕果內的長短花柱雌花的發育不同步；且B期榕果若在授粉 蜂未進駐下，可延長約2至3星期才落果。 牛奶榕在開花物候上有明顯的季節性。雄株在3月至6月有一個春季主要花季，在 其餘期間維持少量榕果花季；每年每株有一至四個花季。雌榕果分別在5月中旬至7月 、7月中旬至11月各有一個夏季主要花季及秋季次要花季；每年每株有一至四個花季 。在花季同步性而言，雄株株內較株間同步，而雌株株間較株內同步；雌、雄株在株 間沒有明顯的同步性，雌株較雄株同步；株內則雌株較雄株為同步；這可有助於授粉 蜂的延續及種子的散播。牛奶榕雌、雄株開花物候與氣溫、降水有明顯的相關；而展 、落葉對於氣溫有明顯相關。 本研究調查共發現一種授粉蜂(Blastophaga nipponica)及犬氏長尾小 蜂(sycoscapter inubiae)及S. sp.二種長尾小蜂。授粉 蜂性比為0.166，犬氏長尾小蜂的性比為0.424；授粉蜂在性比上有明顯偏雌現象。犬 氏長尾小蜂的存在對於授粉蜂沒有顯著影響；授粉蜂的數量對於犬氏長尾小蜂沒有顯 著相關，而授粉蜂雄蜂對於犬氏長尾小蜂有顯著相關；而犬氏長尾小蜂的存在對於授 粉蜂的性比有明顯偏低的現象。

The study is to investigate the morphology of syconium, and phenology, crop cycle of Ficus erecta var. veecheyana, and the lige cycle of fig wasp(Blastophaga nipponica) for the symbiosis between Ficus and their absolute pollinator. Ficus erecta bvar beecheyana is one of the gynodiecious Ficus species; the female syconium are simular outside syconium, but obviously different inside the syconium. The average number of florets is 43.4 in the female syconium; about 68.12% is long sytle female flower, 31.88% is neutral flower. In the male syconium, the average value of florets in 1362.0; about 69.58% is short style female flower, 31.43% is male flower and few of pseudobisexsual flowers. There are about 200.6 fruits in the female syconium, and 349.9 galls in the male syconium on the aberage. No wasp develope in the female figs, and no seed in the male figs. Besides of the difference in the style length, long-style female flowers and short-style female flowers are apparently different in the morphology and structure of stigma, style, and ovule. The phenomenon demonstrates the dimorpholism of female flowers. The neutral flower''s pistillate and stamen are abortive, and the abortibve pistiollate is in the middle of stamen of male flower. The proportions of neutral flowers and male flowers are not significantly different. Therefore, the female syconium may be evolution from the male syconium. Long and short style female flowers are asynchronism in the female and male syconium eace. The figs gell off if the pollinator don''t enter the syconium after 2 to 3 weeks during the B phaes. There was a main sprig crop and few fig''s crop in the other period on the male trees; and a main summer crop and a second autumn crop on the female trees; and there is a temporal gap of two months between male''s and female''s main crops. There are one to three generations of synconia each year in both female and male plants. The character of intertree and intratree crops between male and female crop will be useful to mantain the pollinators and to disperse the seeds. The occurence of male figs of D phase fit better between with the male figs and female figs of B phase. The fruit phenology of F. erecta var. beecheyana was connected with the renewes-fallen leaves, and temperature, rain fall of their habitat closely. There are one Agonid(Blastophaga nipponica) and two non-pollinators, Sycoscapter inubiae and S. sp. developing in the male figs. The sex ratio are 0.166 for pollinator and 0.424 for S. inubiae. The S. inubiae oviposites during C phase after pollinator, it may compete with pollinators for oviposition place, or feed of the larvae of pollinators. The number of pollinators have inapparent correlation to S. inubiae, but the number of pollinator''s male wasp have. However, the S. inubiae have infuence to add the sex ratio of pollinator.