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標題: | 以同功異構?分析臺灣地區白茅族群遺傳變異 The Genetic Variation in Populations of Imperata cylindrica var. major in Taiwan Based on Isozyme Analysis |
作者: | 許秋月 |
出版年 : | 1999 |
學位: | 碩士 |
摘要: | 白茅(Imperata cylindrica)是廣泛分佈於熱帶及亞熱帶地區的一種野生雜草,其中分佈在台灣地區的是I. cylindrica (L.) Beauv. var. major (Nees) Hubb.,多生長在陽光充足的環境,前人研究其形態、ADH酵素活性、RAPD反應和IGS之PCR-RFLP反應,認為竹圍族群為一特殊生態型,而部份RAPD結果亦顯示海岸地區族群可能與內地族群間有分化情形。本研究係利用同功異構?之澱粉膠體水準電泳方法,分析臺灣地區海岸和內地共十一個白茅族群,以檢測族群遺傳變異度及其分佈,其中海岸族群分別為竹圍、觀音、大安溪口、芳苑、布袋、四草和港仔族群,內地族群為汐止、大溪、大埔、南橫族群。總共分析十一種酵素,判讀12個基因座,結果得到,族群的平均異合度期望值(HE)為0.081,平均異合度觀察值(Ho)為0.088,多型性基因座百分比平均為24.2%,而族群間分化指數(FST)達0.1373,顯示臺灣地區白茅族群遺傳變異度偏低,而族群間有相當的分化,符合一般靠分蘗快速擴張族群之物種的特性。白茅傾向逢機性配對(FIS=-0.0973),但基因流傳並非十分通暢(Nm=1.571, >1),天擇作用和大量的逢機性連鎖不平衡所顯+T24示的基因漂變,係影響白茅遺傳結構的主要力量。此外,群叢分析顯示,港仔族群遺傳距離與其他族群相距較遠,可能是EST基因座或與其連鎖的基因座受地域性的天擇壓力所致。而分群結果與形態、生理及DNA分子之研究結果並不一致,論文中將進一步探討。 Imperata cylindrica (L.) Beauv. var. major (Nees) Hubb., widely distributed in tropical and subtropical regions is very common in sunny exposed areas in Taiwan. Previous studies suggested that a population in Chu-wei was a unique ecotype according to the analysis by morphological traits, RAPD markers and PCR-RFLP of IGS. Another findings based on RAPD markers also suggested that populations in coastal area might be differentiated and evolved from inland populations. In this stuty, patterns of genetic variation within and among populations were estimated by isozyme electrophoresis. Samples were collected from 11 populations, namely, Chu-wei, Kuan-yin, Ta-an-chi-kou, Fang-wan, Pu-tai, Ssu-tsao and Kang-tzai populations from coastal area, and His-tzu, Ta-chi, Ta-pu and Nan-heng populations from inland. Allozyme frequency analysis of 12 loci showed that mean expected value of heterozygosity (HE) was 0. 081 and the mean observed value of heterozygosity (Ho) was 0.088. Mean percentage of polymorphic loci was 24.2% and population differentiation coeffeient (FST) was 0.1373. The data implied that depauperate level of genetic variation and marked interpopulation differentiation in cogongrass might be due to rhizomatous propagation and colonizing nature. The populations inclined to random mating (FIS=-0.973) but gene flow was not high (Nm=1.571). Genetic drift, implied by large randomly generated disequilibrim, and natural selection were resposible for the populaton structure. Furthermore, clustering analysis revealed that Gang-zai population had longer genetic distance from other populations based on EST loci, suggesting that local selection might play a predominant role. The possible reasons that grouping result disagreed with previous reports were discussed. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/75034 |
全文授權: | 未授權 |
顯示於系所單位: | 植物科學研究所 |
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