合歡山地區台灣高山田鼠的社會結構

Abstract

囓齒目的社會結構在不同的物種之間有廣泛的分布：從單一個體、雌雄成對個體、以及群聚的社會結構。社會結構的變化不只是在不同的物種之間發生，也有可能在同樣的物種之間產生。研究群聚社會結構的主要原因是他們有可能現在社會的雛形，因此了解群集以及影響群集的因素幫助我們更了解社會系統的演化。在合歡山草原地區，主要的優勢小型哺乳動物爲台灣高山田鼠（Microtus kikuchii）是一個台灣的特有種，過去研究顯示高山田鼠表現空間上活動範圍的重疊。本實驗主要希望檢驗以下假說：（1）高山田鼠在空間上會有群聚的社會結構（2）高山田鼠的社會結構在不同的季節會有不同（3）高山田鼠的社會結構跟一或多個環境因子有相關（4）巢階層對於高山田鼠基因遺傳結構的貢獻度最高。在此研究中，希望透過野外調查以及分子技術以了解高山田鼠的社會結構。本研究定義在不同巢內所補捉的個體數和結構爲該巢的社會結構。採用了螢光粉追蹤法尋找到巢，在各個巢的周圍進行重複捕捉，以了解巢內組成。主要分成三個季節：繁殖季晚期、非繁殖季、和繁殖季前期。同時我們也測量巢周圍的環境因子，如同植被覆蓋度、土壤硬度、落葉層量、族群密度、雌雄比和植被高度。並且利用逐步回歸分析檢驗環境因子和個體數目之間是否有相關。同時也利用分子微隨體技術，了解高山田鼠的族群遺傳結構是否受到社會結構的影響。實驗結果顯示，高山田鼠的社會結構在不同的季節間呈現顯著性的差異，並在繁殖季前期的以群聚爲主要的社會結構。三個季節均有不同的環境因子和該季節社會結構有顯著相關。落葉層的量或深度在三個季節均顯著相關。巢階層對於基因遺傳結構的貢獻度並不顯著，反而是樣區階層的貢獻較為顯著。

The social organization of the Microtus genus exists in a wide spectrum, from solitary male or female units, to male-female pairs, to communal group formation. Social organization shows great inter-and intra-specific variations. The forming of communal groups may be the preliminary forms of society. Therefore the importance of studies in this field has been of much interest in recent years. The Taiwan vole (Microtus kikuchii), an endemic species of Taiwan, is the dominant small mammal at the Hehuan Mt.. Past research shows overlap in the home range of individuals of the Taiwan vole. This thesis hopes to investigate the following hypotheses: 1. The social organization of the Taiwan voles portrays group formation. 2. The social organization of the Taiwan voles varies with the different seasons. 3. The social organization of the Taiwan voles is correlated to one or more environmental factors. 4. The nest scale contributes most to the population genetic structure of the Taiwan voles. The purpose of this study is to examine the social organization of the Taiwan voles through field studies and molecular tools. Defining the number of individuals and composition captured at the same nest as the social organization, using florescent powder tracking and capture-recapture method, the behavior of the Microtus is investigated in three separate seasons: late-breeding season, non-breeding season, and early-breeding season. The environmental factors are also measured at each nest, hoping to examine the relationship between the social organization and the environmental factors and demographic parameters. Using 10 microsatellite loci, this study also addresses the genetic structure of this species, hoping to investigate the genetic diversity at various scales of population structure. The results show that the social organization shows significantly different patterns between seasons, and that group formation is the main social organization of the early breeding season. The social organizations of the three seasons each correlate to different factors, with litter amount or depth a significant factor in all three seasons. The nest scale does not contribute significantly to the population genetic structure, while the site scale shows higher contribution.