共用一巢制的冠羽畫眉之遺傳結構與親緣關係

Abstract

自從W.D. Hamilton提出總和利益的概念擴充演化論後，直接利益與非直接利益的重要性與互動個體間的親緣關係，在社會行為的演化的討論上充滿了爭議。要解決這個問題，了解動物間的親緣關係是其中關鍵的一環。本研究針對共用一巢制合作生殖的燕雀目鳥類—冠羽畫眉(Yuhina Brunneciceps)，瞭解其合作個體間的基因結構。在鳥類中，共用一巢是較為稀有的合作生殖方式，指的是多於一隻的同性別個體在共同的巢內擁有子代並提供親代照顧。冠羽畫眉大部分個體均行合作生殖，其合作生殖群通常由一到三對一夫一妻制的配偶組成，偶有單隻未配對個體。大部分的子代在離巢後不久即播遷離開出生領域。此研究使用了九個微隨衛星體座分析冠羽畫眉合作群內個體間的親緣關係。合作個體間的親緣關係平均低，且群內個體間的親緣並未顯著高於群間個體的親緣關係。因此直接利益可能是冠羽畫眉合作生殖的主因。然而，群內特定位階個體，如未配對的雄鳥或是最高位階的雌鳥，與群內同性別個體的親緣關係顯著高於族群內逢機取樣。因此，親緣關係仍然可能影響冠羽畫眉的播遷行為與合作群體組成。基因分析可以揭露合作群體內個體間的真實親緣關係，因此，有助於我們瞭解直接利益與間接利益在社會行為演化中的相對重要性。

The relative importance of direct and indirect fitness and, thus, the role of kinship in the evolution of social behavior are much in debated. Studying genetic relatedness between interacting individuals is crucial to solve the puzzles. Here we studied the genetic structure of the joint-nesting passerine species, Taiwan yuhina (Yuhina Brunneciceps). The breeding unit of yuhinas mainly comprised one to three socially monogamous pairs, and most offspring dispersed after fledging. We used nine microsatellite loci to investigate the genetic structure of their cooperative breeding groups. The average genetic relatedness between same-gender co-breeders was low and we did not detect significant differences of relatedness between and within co-breeding groups. In addition, the fact that most yuhinas breed in the groups implies that there should be strong direct benefit of the joint-nesting behavior. However, unpaired males and alpha females were significantly closer related to the same-gender co-breeders. This may suggest that relatedness still play some roles on the dispersal and group formation in yuhinas. In conclusion, the genetic analysis can reveal actual relatedness pattern, which is crucial to understand the evolution of cooperative behavior. The study of non-kin cooperating species could provide important insight to determine the relative importance of direct and indirect fitness to the evolution of social behavior.