陽明山地區牛奶榕(Ficus erecta Thunb var.beecheyana)與牛奶榕小蜂(Blastophaga nipponica)的共生生態

Abstract

榕屬(Ficus spp.)與榕果小蜂(fig wasp)因長時間的共同演化，二者間有密切的共生關係，但相關研究多以雌雄同株種類為主，本論文以雌雄異株的牛奶榕為題材，研究榕果各果期形態、發育、榕果開花物候週期、小蜂的行為，並探討寄生蜂的影響。自民國82年9月至84年9月，每週定期調查陽明山地區的31棵雄株及50棵雌株牛奶榕，記錄榕果各發育期的大小、外形、數量，記錄葉的變化，並不定期採集B、D期榕果以顯微攝影機拍攝小蜂的行為，另於84年6?8月以黏蟲及套袋實驗研究小蜂的種間關係。陽明山地區的牛奶榕的結實有明顯季節性，集中在春夏季，雌果花期由6月開始，株內變異較大；雄果花期由4月開始，株間變異較大。D期雄果數量整年都很少，所以釋出的小蜂量亦少，故推測陽明山區小蜂族群量低且波動不大。雌雄B期榕果數量高峰出現的時間有錯開現象，雌果B期與雄果D期與配合較佳，而雄果B期與雄果D期則呈零星搭配。本區的牛奶榕果內共發現一種榕小蜂(Blastophaga nipponica)及一種寄生蜂(Sycoscapter inubiae)。榕小蜂無明顯之授粉行為，且無特化之攜粉構造，可推知牛奶榕小蜂為被動傳粉。榕小蜂於雌雄B期榕果中皆有試插行為，但僅在雄果中有產卵行為。寄生峰的雄蟲有打鬥的行為而榕小蜂雄蟲則無，且寄生峰的性比為0.45高於榕小蜂的0.19，其生殖策略支援Local mate competition理論。由隨機觀察及黏蟲實驗發現，寄生蜂僅於C期產卵，較榕小蜂產卵時間晚，由套袋結果發現寄生蜂的存在顯著會降低榕小蜂的比例，由此推測本種寄生蜂可能需依賴榕小蜂刺激榕果，並與榕小蜂競爭產卵場或以榕小蜂幼蟲為食。

The symbiosis between Ficus and fig wasps become obligative and specific due to long history of coevolution. Monoecious species have been the focus for the studies in the past. I selected dioecious Ficus erecta as study object. My purposes are investigating the morphology and development of figs, their phenology, behaviors of fig wasps and the influence of parasite wasps of 31 male trees and 50 female trees at Yang-Ming-Shan National Park. During the period of September 1993 to September 1995, the size, shape, and developmental stages of the fig as well as leaf change were recorded once a week. In addition, B and D phase figs were picked, opened, and Vedio taped with microcamera. In order to study the inter-species relationship of fig wasps, the trap and bag manipulations were executed from June to August 1995. The phenology of F.erecta showed an obviously seasonal change, crops of figs aggregate in spring and summer. The male crops started to grow in April, and the chronicle synchronization was greater among different trees than among different crops. The female crop started to grow in June, and the chronicle synchronization among trees were less than among crops. The number of the male figs at D phase have been very few each month. Therefore, the population size of fig wasps of this area could be small with little fluctuation. An obvious gap was shown between the peaks of B phase figs of male and female trees. The occurrence of male figs of D phase fit better with that of female figs of B phase, and show sporadic fitting with male figs of B phase. Inside the figs, only one species of pollinator wasp (Blastophaga nipponica) and one species of parasite wasp (Sycoscaper inubiae) were found. Due to lack obvious pollinating behavior and structures of pollen packet, the pollinator wasps could pollinating figs with passive mechanism. The pollinators displayed only ovipositor insertion-testing behavior inside the female figs, while they showed complete ovipositing behavior inside the male figs. The male parasite wasps showed fighting behavior, while the male pollinator wasps did not. The sex ratio were 0.45 for the parasites and 0.19 for the pollinators. Therefor, this case support the Local mate competition theory. parasite wasp oviposits during C phase after pollinator wasp. The existence of parasite wasp apparently reduced the ratio of pollinator. Therefore, the iner-specific relationship between fig wasps were inferred as that parasite wasps rely on pollinator wasp to stimulate figs, compete with pollinator wasp for oviposition place, or may feed on the larvae of pollinator wasp.