臺灣產薯蕷科植物核酸多形性在分類上應用之研究

Studies on the Classification of Dioscoreaceae in Taiwan Employing the RAPD Data

臺灣原生及栽植的薯蕷科植物只有薯蕷屬1屬，其多生長在低、中海拔的次生林林緣或平地路旁；生育地通常為坡地、排水良好的河床地或砂地。該屬植物在外形上呈現廣泛多樣性表現，且易產生多倍體，兩者因素交互影響，以致各地出現的族群變異形式相當多。歷年各學者由不同研究領域，含括外部形態以至分子生物技術等方面的研究結果，對臺灣產薯蕷屬植物物種的認定諸多分歧，有6種至14種5變種等不同分類處理意見。本研究乃利用RAPD分析臺灣產薯蕷屬植物，綜合比較本屬各種植物的形態特徵，歸納其種形成的有關情節以提供系統分類之參考。就採集材料的RAPD實驗結果顯示，10種1變種129族群間彼此的遺傳相似性係數介於0.56－0.75間。大部分變異存在於個體間為主，呈現出族群內個體間多樣的遺傳組合：或因為適應殊異的生育地環境因子影響內在的遺傳物質，如裡白葉薯榔、華南薯蕷、戟葉田薯、日本薯蕷之三變種等族群；或因純粹的地理區隔致使生殖隔離而呈現不同基因流，而將北、中、南及東部等地區所含括的族群區隔開來，如大薯、山芋與臺灣薯蕷等族群。此外，根據日本薯蕷三變種之外形鑑定特徵以資區分彼此，佐以RAPD分析結果進行確認，而仍認為宜處理為三變種。綜合歸納核酸多形性與形態特徵的研究結果，可將臺灣產薯蕷屬植物處理為13種4變種。 The only one genus Dioscorea of Dioscoreaceae are indigenous or cultivated in Taiwan. They often grow in the slope fields of lowlands and somewhat high mountains. These plants are highly phenotypically variable and result in many polyploid species complexes distributing widely. Therefore, they are dividing into many close taxa that are difficult to classify and called 'Dioscorea species complex'. Each taxonomist studied from different fields including morphological and molecular approaches, and resulted in different systematic treatments of the Dioscorea plants in Taiwan. In order to understand the interrelationship among the species of Dioscorea and the mechanisms of their speciation, we employ the RAPD method to study those plants of 129 populations collected from Taiwan. The RAPD dendrogram reveals the genetic similarity coefficients of the 11 species 4 varieties and 129 populations being between 0.56-0.75. Most evolutionary variations mainly appear among the individuals of those plants and they show different genetic combinations: the different environments of sites affect their internal genetic genes, such as D. cirrhosa Lour., D. collettii Hook. f., D. doryphora Hance, and the 3 varieties of D. japonica Thunb.; the geographical isolation results in the reproductive isolation of those plants and derived from the different gene flows, such as D. alata L., D. bulbifcra L., and D. formosana R. Knuth. We still assign the 3 varieties of D. japonica Thunb. by means of their diagnostic characteristics of morphological appearance combined with the RAPD results. Based on this study, all the plants of the Dioscorea in Taiwan could be classified as 13 species and 4 varieties.

The only one genus Dioscorea of Dioscoreaceae are indigenous or cultivated in Taiwan. They often grow in the slope fields of lowlands and somewhat high mountains. These plants are highly phenotypically variable and result in many polyploid species complexes distributing widely. Therefore, they are dividing into many close taxa that are difficult to classify and called 'Dioscorea species complex'. Each taxonomist studied from different fields including morphological and molecular approaches, and resulted in different systematic treatments of the Dioscorea plants in Taiwan. In order to understand the interrelationship among the species of Dioscorea and the mechanisms of their speciation, we employ the RAPD method to study those plants of 129 populations collected from Taiwan. The RAPD dendrogram reveals the genetic similarity coefficients of the 11 species 4 varieties and 129 populations being between 0.56-0.75. Most evolutionary variations mainly appear among the individuals of those plants and they show different genetic combinations: the different environments of sites affect their internal genetic genes, such as D. cirrhosa Lour., D. collettii Hook. f., D. doryphora Hance, and the 3 varieties of D. japonica Thunb.; the geographical isolation results in the reproductive isolation of those plants and derived from the different gene flows, such as D. alata L., D. bulbifcra L., and D. formosana R. Knuth. We still assign the 3 varieties of D. japonica Thunb. by means of their diagnostic characteristics of morphological appearance combined with the RAPD results. Based on this study, all the plants of the Dioscorea in Taiwan could be classified as 13 species and 4 varieties.