| 摘要: | 牛樟為台灣特有之常綠闊葉喬木，其材質優良，經濟價值高，因此遭大量砍伐與盜伐，加上其結實量稀少，天然下種困難等因素而導致族群日益減少，目前已被列為保育類植物。由於目前牛樟的遺傳背景研究缺乏，因此本研究以親源地理與演化關係作為研究重點，希望能得知牛樟的遺傳變異分布以及族群演進歷史，以了解牛樟過去的族群變動歷史，建立牛樟的遺傳背景知識，期望能提供有效的牛樟保育遺傳資訊，以供今後牛樟保育工作之參考。
本研究以牛樟葉綠體 DNA trnL-trnF、petG-trnP 兩基因區間序列，以及牛樟細胞核 DNA LEAFY 基因之第二段 intron 序列，共分析 106 個牛樟樣本之遺傳結構及親緣地理關係。分析結果顯示牛樟葉綠體 DNA 非常保守，兩段序列合併後得到之序列長度為 792 bp，具有 9 個多型性位點，共有 7 個單套型。而 LEAFY 基因 intron 序列長度為741 bp，共包含 16 個多型性位點，全為 parsimony informative sites，共具有 26 個單套型。而無論是以中性假說檢測、單套型歧點分布（mismatch distribution）的分析結果或是單套型基因譜系圖來推斷，結論皆傾向牛樟族群曾經發生過族群擴張事件，並且由 Skyline plot 圖得知牛樟族群近來正遭受「瓶頸效應（bottleneck effect）」，族群數量減低。此外，由族群遺傳歧異度與對偶基因豐富度之貢獻度分析結果顯示，牛樟有多個起源中心，並且指出牛樟在冰河時期之避難所可能有三處，分別位於台灣西北部至中部一帶之新竹大坪、苗栗大湖、南投武界族群，以及西南部之高雄多納、新威族群，與台灣東南部花蓮玉里、富里、秀姑巒族群一帶、台東錦屏、關山族群，其中以西南部以及東南部兩處之避難中心範圍較大。
The purpose of this study is to examined the patterns of genetic variation, demographic history, haplotype relationships, and infer the possible location of refuge in Taiwan during the Pleistocene and the recolonisation route of Cinnamomum kanehirae Hay. (Lauraceae). This study examined the spatial pattern of chloroplast DNA and nuclear DNA variation in a total of 21 populations of C. kanehirae, including 106 individuals sampled throughout its distribution range. PCR amplification of two cpDNA intergenic spacer fragments and the second intron of LEAFY gene in nuclear DNA, respectively using universal primers (trnF-trnL, petG-trnP) and primer c.k.LFY1-c.k.LFY2, modified from LFY1-LFY2 (Frohlich and Meyerowitz, 1997); and then obtained the nucleotide sequences variation.
The result of neutrality test showed a significant negative statistic departure from equilibrium, indicating that C. kanehirae may have been increased in population size. This result was consistent with mismatch distributions analysis and the haplotype network reconstructed from the computer program TCS. However, the result of Skyline analysis not only resvealed an population expansion event, but also can be used to infer a bottleneck effect occurring in the populations of C. kanehirae. Furthermore, this study supports the multiple relict refugia hypothesis for C. kanehirae. Populations of C. kanehirae in Daping, Dahu and Wujie in the north-central area west of the Central Mountain Rrague (CMR), populations Duona, Xinwei in the southwest area of the CMR, and the populations Yuli, Fuli, Xiuguluan, Jingping, Guanshan in the southeast area of the CMR were the diversity centers. These three areas were the possible refugia centers during the Pleistoncene glacial periods in Taiwan. |
