台灣地區青剛櫟粒線體DNA多型性之研究

Abstract

本研究藉由粒線體DNA (mtDNA)多型性的變異，來探討台灣地區分佈最廣的殼鬥科植物－青剛櫟(Cyclobalanopsis glauca)之親緣地理關係。其樣本取自台灣25個族群、大陸廣東、香港及日本京都、九州、鹿兒島、沖繩島中部、南部各一個族群，共32個族群，並挑選其中123株進行研究。本研究中共測試了六段基因，不過僅兩段基因具有多型性：nad4/3-nad4/4r與nad7/2-nad7/3r，定序結果挑選出intron區域，並將兩段序列合併，其總長度為1788bp (nad4/3-4:541bp, nad7/2-3: 1247bp)；而多型性位點(polymorphic sites)包括了4個點突變(point mutation)及1段8 bases的缺失(deletion)，其中大約有八成的變異存在台灣東部族群。經由TCS軟體分析，共可得到6個單套型(haplotype)，其中a型為祖先型(ancestral haplotype)，廣泛分佈在東亞地區，從日本京都至香港皆有，在台灣a型也是廣泛分佈；c型則零星分佈在西部、大陸廣東還有東部的蘇澳；b、d兩型為台灣東部族群所特有，且呈南北走向分佈；e型集中在東南部的牡丹、太麻?及陽明山（1株）；f型為香港族群所特有的。這6個單套型中，有5個皆在台灣出現。台灣本島具有很高的族群間遺傳分化指數(GST＝0.584)，全部族群遺傳歧異度亦不低(HT＝0.631)，而由核甘酸、單套型歧異度來看，台灣族群比國外族群具有更高的歧異度；進一步比較台灣東西部族群的差異，發現中央山脈為青剛櫟族群在間冰期族群向北遷移時，東西向基因交流的主要障礙。本研究中發現東部共出現5個單套型，包括了b和d單套型，東部族群的核甘酸、單套型歧異度都比西部族群高，配合過去地層花粉的紀錄，大致上可推論出臺灣東南部可能為青剛櫟在冰河時期的避難所。

The spatial pattern of mitochondrial DNA (mtDNA) variation in Cyclobalanopsis glauca (Thunb. ex Murray) Oerst. (Fagaceae) was studied in 123 trees collected from Taiwan (25 populations), Japan (3), the Ryukyus (2), Hong Kong (1), and China Mainland (1). By sequencing 2 mtDNA intron fragments using universal primers (nad4/3-nad4/4r and nad7/2-nad7/3r), we revealed a total of 1788 bp and five polymorphic sites (nad4/3-4: 541 bp, nad7/2-3: 1247 bp). Among them, four sites were point mutation, and one was resulted from deletion (8 bases). This gives rise to a total of 6 mtDNA haplotypes by TCS software. The level of differentiation among the populations studied is relatively high (GST = 0.584). Eighty percent of the polymorphic sites exist only on the east Taiwan, giving all of the rare derived mtDNA haplotypes. One ancestral haplotype (a) is widely distributed in East Asia. The Central Mountain Ridge (CMR) of Taiwan has effectively interrupted gene flow between populations on both sides. East of the CMR, two dominant haplotypes b and d show spatial genetic structure, and north-south recolonization route. Taken together with palynological record, this study favors a contention that the southeastern Taiwan as a potential refugium during the maximal ice glacier.