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標題: | 豬母乳榕樹上『榕-小蜂-蟻』群聚的種間交互關係 Species interactions in fig-wasp-ant community on Ficus benguetensis Merrill |
作者: | Shang-Yang Lin 林上揚 |
指導教授: | 周蓮香(Lien-Siang Chou) |
關鍵字: | 豬母乳(Ficus benguetensis),物候,螞蟻,交互關係,防禦, Ficus benguetensis,Phenology,Ants,Interactions,Defense, |
出版年 : | 2016 |
學位: | 博士 |
摘要: | 榕屬植物及其授粉榕小蜂的共生關係(膜翅目;榕小蜂科)是義務性互利共生的經典例子之一。然而,在此互利共生關係中提供給共生夥伴的資源亦吸引了許多其他物種,包括非授粉小蜂和螞蟻。本論文主要研究對象為雌雄異株的榕屬樹種,豬母乳(Ficus benguetensis)及其上膜翅目昆蟲,探討下列問題:榕屬植物如何藉由榕果物候的性別差異來影響榕果與榕小蜂之間的互動關係、評估非授粉小蜂和螞蟻對榕蜂共生關係穩定性的影響,以及榕屬植物針對非授粉小蜂的防禦機制等。首先,我在台灣北部新店地區進行為期兩年的榕果物候調查。我發現豬母乳不僅在榕果物候上有明顯的性別差異,在雌雄樹上,榕果生長的位置也有極大的差別,雄樹全年連續結果,榕果大多生長於樹幹與較低的枝條,而雌樹僅於夏季結果,榕果主要生長於樹冠。這些差異可能具有共生演化的選汰優勢,雄樹連續結果以維持授粉蜂族群的穩定,而雌樹在樹冠層結果則有助於種子的傳播。接著,為了量化非授粉小蜂對授粉榕小蜂的影響,我在富陽生態公園進行接蜂套袋的試驗。操縱非授粉小蜂的數量並追蹤後續榕果的發育和小蜂的產出情形,我發現隨著寄生型的延腹小蜂(Philotrypesis sp.)密度的增加,落果比例顯著上升而雄榕果產出的授粉榕小蜂的比例顯著下降。再從數學模擬的結果發現,這種選擇性落果可以有效降低非授粉小蜂的族群並提高榕樹和授粉小蜂的適存度。除了榕小蜂外,螞蟻是榕蜂共生關係中相當常見的昆蟲。我在新店豬母乳樣區,2年調查期間總共觀察到6253隻分屬13種的螞蟻。同域共存的物種普遍預測有高度的棲位重疊和種間競爭。因此,我分析螞蟻群聚的空間、時間的變化,種間的相互作用和榕樹提供的糧食資源對螞蟻群聚的影響。我發現螞蟻的數量分別和溫度及榕果的數量呈現正相關。榕果提供的食物資源隨著果期而改變,而各別螞蟻種類的數量和不同期別的榕果之間的相關性,可能反應出他們的食性。在空間分析上沒有檢測到種間競爭排斥的現象,這樣的現象可能是因為螞蟻優勢性的降低或是榕樹提供的食物資源的特性(包括資源的可取得性、時序變化和食物資源特性等)所導致。我推論榕屬植物上的螞蟻群聚可能透過資源分化的方式共存。最後,為確定螞蟻對榕蜂共生關係之影響,我在富陽生態公園進行螞蟻的排除實驗。我發現失去螞蟻的保護,發育到成熟期的榕果比例降低,同時,成熟期的榕果中總小蜂數量及授粉小蜂數量皆呈現顯著下降,顯示螞蟻的間接性防禦是維持榕蜂互利共生關係相當重要的一環。為了了解榕樹與螞蟻之間間接性防禦機制的建立,我也測試了螞蟻對不同期別的榕果氣味的反應並利用高效陰離子交換層析檢測榕果表面的醣類。結果發現皺家蟻特別偏好花間期的榕果,此外,榕果表面的醣類組成會隨果期變化,相較於雌花期,花間期榕果上的醣類,蔗糖比例的增加可能與螞蟻的共生相關。本論文探討了榕樹和相關的膜翅目昆蟲之間的相互作用,為榕屬植物與其上昆蟲群聚及互利共生的穩定機制的研究提供了重要的方向。 The interaction between figs (Ficus spp.) and their pollinating fig wasp (Hymenoptera: Agaonidae) is one of the classic examples of obligate mutualism. However, the rewards that provided by the mutualistic partners to one another also attract amounts of species, ranging from the nonpollinating fig wasp to ants. This dissertation focuses on one dioecious Ficus species, F. benguetensis, explores the following issues: interactions between fig trees and fig wasps via fig phenology, as well as the impact of nonpollinating fig wasps and ants that might influence the stability of mutualism, and also the unknown mechanisms underlying defense against those exploiters. To understanding the fig phenology of F. benguetensis, which their pollinating wasps, Ceratosolen wui, rely on, I conducted a two-year survey on 17 trees (11 male and 6 female trees) of dieocious F. benguetensis in Xindian District, New Taipei City, Taiwan. I found F. benguetensis showed clear sexual difference between sexes, not only in the phenological patterns but also the positions that figs produce within one tree. Male continues fruiting mainly on the trunk, while female only produces figs in the suitable season and mainly on the twig. This difference could be the results of evolutionary response that provides a selective advantage by maintaining the pollinator population understory on male tree and facilitating the uptake by seed dispersers in canopy on female tree. Next, in order to quantify the impact of the nonpollinating fig wasps on the pollinators, I conducted bagging experiments in Fu-Yang Eco-Park. I manipulated the number of nonpollinators (0-5 individuals), Philotrypesis sp., to each fig and traced their developmental outcomes: complete growing to wasp-releasing phase, total numbers of emerged wasp, and the proportion of pollinating wasps. From 51 figs succeeded from bagging experiments, I found high density of Philotrypesis sp. did significantly increase the fig abortion rates and decrease the number of pollinators emerged. Then, from mathematic modeling, I found selective abortion of fig in early stage can serve as an alternative defensive mechanism by depressing the population of nonpollinating fig wasp and elevates the fitness of fig tree and their pollinating wasp. On the community of Ficus-wasps, ants were common attendants on fig trees. I have observed and collected 6253 ant individuals belonging to 13 species during two years survey in Xindian sampling area. The co-existed sympatric species were generally predicted to experience high levels of niche overlap and competition. I examined the spatial, temporal variation of ant communities, and also the inter-specific interactions and the effect of the food resource provided by fig tree. I found the ant abundance was positively associated with the temperature and the fig abundance. Correlations between fig abundance in different stages and ant abundance of each species could be reflecting their feeding habits. No species segregation pattern (i.e., interspecific competition) was detected in spatial analysis. It could be due to the absence of dominance and other factors related to resource, including resource accessibility, temporal variation and nature of the resources. I suggest that the coexistance of 13 ant species on F. benguetensis (no evidence of competition) was shaped by resource partitioning. Finally, to determine the role of ants played on the interaction between fig tree and the associated wasps, I conduct ant-exclusion experiments at Fu-Yang Eco Park. Comparing with control groups, I found that the proportion of pollinator during emerging phase was significantly drop, as well as the proportion of figs that successfully grows to wasp-releasing phase and the total numbers of emerged wasp. I also examine the preference of ant to fig at different stages and quantify the sugars (carbohydrates) deposited on the surface of figs to explore the chemical cues that induced this indirect defense. This dissertation explores previously unstudied aspects of the interactions between Ficus and associated hymenopteran insects, and provides important directions for future study of this ecologically important issue. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/51174 |
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顯示於系所單位: | 生態學與演化生物學研究所 |
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