灰頭織巢鳥群內繁殖衝突之研究

Within-group Conflict in the Cooperatively Breeding Grey-capped Social Weaver (Pseudonigrita arnaudi)

施怡伸(Yi-Sheng Shih)

指導教授 ： 沈聖峰

國立臺灣大學/生命科學院/生態學與演化生物學研究所/碩士(2018年)

https://doi.org/10.6342/NTU201800449

摘要

動物會形成群體，藉由成員之間的合作得到利益，但同時也會因利益分配而產生衝突。了解社會動物如何解決衝突以維持群體的穩定，是了解動物社會行為演化的關鍵。親屬選擇理論 (kin selection theory) 預測個體會與傾向與親戚合作，然而許多研究發現衝突反而也會發生在親戚之間。相對於非親戚，親戚間是否因衝突後可獲得較高的直接利益或代價較低，因而能解釋親戚間衝突的存在，仍需進一步探討。灰頭織巢鳥 (Pseudonigrita arnaudi) 為行合作生殖的鳥類，母鳥擴散而形成父系的階層式社會，其中踢蛋行為 (conflict egg-tossing) 是成員間衝突的重要形式。我們於2012 - 2017年記錄織巢鳥繁殖、踢蛋事件和社會網絡資料，比較踢蛋後的繁殖狀態作為判斷衝突獲得的繁殖利益，並檢視群內親緣關係對群內衝突程度的影響。結果顯示群內親緣關係越高，群內平均衝突程度 (平均踢蛋次數) 越高。踢蛋者在踢蛋後繁殖的比例較高，親戚間的社會互動關係不受踢蛋事件影響，個體平均子代數也不變。反之，踢蛋發生在非親戚間時，個體互動頻率降低，平均個體子代數降低，顯示與親戚衝突的代價較小。進一步利用假巢放置假蛋以觀察踢蛋行為，公鳥親緣關係高的群，踢蛋者比例亦較高，支持自然巢的結果。本研究發現在親屬選擇理論的架構下，若衝突的利益和代價隨著衝突雙方的親緣關係改變，在衝突的直接利益高或代價較低的情形下，親戚間的衝突便仍會發生。

關鍵字

社會衝突 ； 親屬選擇理論 ； 合作生殖 ； 灰頭織巢鳥 ； 踢蛋

並列摘要

While living in groups has benefits for animals, conflict could arise over the share of resources among group members. Understanding the mechanism of conflict resolution is key to explaining evolution of sociality. Kin selection theory predicts that individuals would prefer to cooperate with kin for acquiring indirect benefits. However, conflict among kin is still common and awaits more detailed examination. Conflict among kin may occur when direct benefits are high and incurred costs are insignificant. We studied grey-capped social weavers (pseudonigrita arnaudi) to investigate the costs and benefits associated with conflict behavior (i.e., egg tossing). Grey-capped social weavers are cooperatively breeding birds where females disperse and males stay and form kin-based groups. We collected data on breeding, egg tossing and social networks from 2012 to 2017 in order to understand reproductive benefits and social interactions after conflict tossing. We found that the conflict level (per capita tossing events) is higher in groups with higher relatedness among males. The proportion of breeding attempts after tossing is higher in the egg tossers than in the non-tossers in the groups, which suggests a direct benefit of tossing. In addition, social interactions remained at the same level after tossing in the groups with high relatedness among males, which suggests the inherent cost in conflict is low for kin. In contrast, social interactions and per capita productivity decreased after tossing in the groups with low relatedness among males. We further tested the consequences of tossing by inducing tossing events with fake eggs in fake nests. The groups with more related males also had higher proportions of tossers in the fake nest experiment. Our study suggests that though kin cooperation is well recognized, conflict among kin could still occur when cost is low and direct benefits are high.

並列關鍵字

social conflict ； kin selection theory ； cooperatively breeding ； grey-capped social weaver ； egg tossing

參考文獻

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