梅峰地區冠羽畫眉合作生殖群體之子代性別分配

Nestling sex allocation of a joint-nesting Yuhina brunneiceps population at Meifeng

傅淑瑋(Shu-Wei Fu)

指導教授 ： 袁孝維

國立臺灣大學/生物資源暨農學院/森林環境暨資源學研究所/碩士(2005年)

https://doi.org/10.6342/NTU.2005.01924

摘要

本研究旨於探討行合作生殖之冠羽畫眉群體子代性別分配情況。研究地區內觀察到冠羽畫眉多以聯合築巢制進行繁殖，且於繁殖群體內，成員間位階關係明顯。過去研究發現不同位階雄性間在翼長上有顯著差異，但雌性間則否；推測親鳥投資之效應可能影響於雄性之效果較雌性大。本實驗測試Trivers & Willard假說，親鳥是否會根據本身狀態及環境狀況而調整產下子代性別。野外工作項目包括行為觀察、繫放、收集親鳥及子代血樣；並將野外收得之血樣利用分子技術鑑定性別及親子關係。統計分析結果發現，子代性別顯著與母鳥位階有關，高位階母鳥較低位階母鳥產較多兒子。此外，當以巢為單位，分析各巢中雄性子代所佔比例時，發現原始性比與繁殖時間、繁殖群大小及一巢子代數有關。當該巢的繁殖時間於繁殖季初期，繁殖群較小且一巢子代數較少的情況下，一巢雄性比較高。在二次性比方面，發現繁殖時間及一巢子代數仍顯著與一巢雄性比有關。本研究結果支持Trivers & Willard假說，當親鳥位於低位階、繁殖末期、巢中子代數較多等資源較有限的情況下，一窩子代中雄性比例較低。

關鍵字

冠羽畫眉 ； 聯合築巢制 ； 合作生殖 ； 性比 ； 母鳥位階 ； 繁殖時節

並列摘要

The aim of this study was to examine the nestling sex allocation of a joint-nesting population of Taiwan yuhina (Yuhina brunneiceps). Most of Taiwan Yuhina breeds with joint-nesting strategy in the study site, and the linear hierarchy relationship within group members is obvious. Dominant males had larger wing chords than subordinate males, but there was no difference of body size between dominant and subordinate females. We assumed that the condition of males was more influenced by parental investment than that of females. I conducted the study at Meifeng area during 2003-2004; field work included observing the hierarchy and pair bond of breeding group members, and taking the blood samples from adults and nestlings. I then employed molecular techniques to determine the sex and estimate parentage of nestlings. Results showed that nestling sex was associated with maternal status, and dominant females produced more sons than subordinate females. When sex ratio of broods was analyzed, I found that primary sex ratio was influenced by timing of breeding season, group size, and brood size. The proportion of sons decreased as the season progressed and when group size and brood size were larger. Secondary sex ratio was also influenced by timing of breeding season and brood size. The results supported the predictions of Trivers and Willard hypothesis, females manipulated offspring sex in relation to maternal status and sex ratio of broods was female-biased when the resources was limited in late breeding season and when brood size was larger.

並列關鍵字

sex ratio ； Yuhina brunneiceps ； joint-nesting ； cooperative breeding ； maternal status ； timing of breeding season

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