Synchronization of fig (Ficus microcarpa L. f.) abundance and pollinator (Eupristina verticillata: Agaoninae) population dynamics in northern Taiwan

北臺灣正榕(Ficus microcarpa L. f.)榕果豐度與其授粉蜂(Eupristina verticillata: Agaoninae)族群波動之同步性

陳穎儒(Ying-Ru Chen) ； 吳文哲(Wen-Jer Wu) ； 周蓮香(Lien-Siang Chou)

《國立臺灣博物館半年刊》 57卷2期 (2004/12) Pp. 23-35

https://doi.org/10.6532/JNTMA.200412_57(2).0003

摘要

Synchronization of different fig crops in a fig tree community has been crucial for the co-evolution of mutualisms between figs and their pollinators. Female-phase (B-phase) figs in one crop, which are receptive to pollinators, must be synchronized with male-phase figs, from which fig wasps are emerging(D-phase), in another crop. From August 1992 to November1998, 35 Ficus microcarpa L. f trees were surveyed weekly in northern Taiwan. The number of figs on each tree, their developmental phase, the number of foundress wasps in sampled figs, the pollinator occupancy rate and the population size index were counted and estimated. Each year, there were two fig gaps, periods when there were no figs on the trees. Based on the fig gaps, we separated the fig crops into two flowering seasons, winter-spring (WS) and summer-fall (SF).WS crops averaged 10.28 ±0.70 weeks in length and SF crops averaged 5.97±0.18 weeks. WS crops lasted significantly longer because the B-and C-phases of fig development were prolonged. Thus, Ficus microcarpa may have adapted to low numbers of fig wasps during the cool winter by extending the availability of B-phase figs, and increasing their attractiveness. Based on the number of fig wasps found in B-phase figs, wasps inclined to enter younger figs. The pollinator population fluctuated regularly and it was correlated with the co-occurrence of B- and D-phase figs. However, in this F microcarpa community, the first peaks of pollinator population in the early spring appeared on the week existing only B-phase figs in the field. The peaks were crucial for reestablishing the pollinator population and provided the base from which large, SF populations arose. The early peaks in wasp abundance might result from fig wasps dispersing from southern Taiwan, or from wasps emerging from overlooked, local refuges, or alternative hosts.

關鍵字

Fig ； pollinators ； synchronization ； population dynamics ； Taiwan

並列摘要

在榕樹與其授粉蜂的互利共生演化中，榕樹花期的同步性是一個十分關鍵的研究重點。授粉蜂於榕果雌花期（B期）進駐榕果產卵，子代於榕果雄花期（D期）鑽出，因此，榕樹株間B、D期的配合對授粉蜂族群的延續十分重要。自1992年至1998年於臺大校區每週調查35株正榕植株，記錄榕果數目及授粉蜂族群之消長，發現榕樹族群可分為冬春季及夏秋季兩個花季，兩季間各有十分規律的花間休止期。冬春季花季較長，約為期10.28±0.70週，夏秋季之花季則為期5.97±0.18週。冬春季比夏秋季延長的原因在於雌花期延長，此情形顯示榕樹在冬春季為了等待極少數的授粉蜂族群，有延長雌花期的現象，以增加吸引授粉蜂的機會。不過，即使榕果B期的直徑隨著時間延長而增大，授粉蜂仍然傾向選擇直徑小的B期榕果進駐。另外，授粉蜂的族群波動與B、D期榕果的共存指數有極高的相關，可見授粉蜂於榕果外的時間十分短暫。不過每年春季出現的第一批授粉蜂，當週並無D期榕果存在，可見每年第一批蜂是重新於樣區建立的，且到夏秋季可達到最高峰。推論春季的第一批授粉蜂之來源有三個可能：(1)由南方遷移過來，(2)本身存在於樣區少數榕果中，或是(3)具有代用寄主。

並列關鍵字

正榕 ； 榕果 ； 授粉蜂 ； 花間休止期 ； 同步性 ； 族群波動 ； 北臺灣