台灣產豆蘭屬植物系統分類研究

Abstract

蘭科 (Orchidaceae) 豆蘭屬 (Bulbophyllum Thouars) 植物為泛熱帶性分布的植物類群，同時也是全世界最大的屬，目前有超過2000個以上的物種被命名。台灣植物誌第2版所記載之台灣產豆蘭共有21個物種，後續數年的野外觀察又發表了數種新物種。至今日台灣的豆蘭屬植物目前共發表了30個分類群，其中共包括23個種和7個變種。本研究使用了28個台灣產豆蘭分類群資料，同時也加入非台灣產豆蘭之序列一併分析，分析方法為使用3種葉綠體分子標記：matK局部序列、trnC-rpoB intergenic spacer以及trnL-trnF intergenic spacer之局部序列進行PCR擴增並定序，再使用核酸排序後，進行最大簡約法、鄰近相接法 以及貝葉氏導出式分析來分析譜系關係，以期建立台灣產豆蘭屬內之親源關係，並佐以外部特徵來探究特徵演化之歷程。 三種葉綠體分子標記分析所得之演化樹雖不盡相同，但大致上之分群組成仍然相似；單花類型的物種在台灣產豆蘭屬中較靠近基群的位置，尤以無假球莖單花類型者最接近基群；而側萼片修長且相貼的捲瓣蘭節物種形成台灣產豆蘭核心的一群，而與側萼片較短的捲瓣蘭物種分開。而特徵演化的追蹤，也可發現捲瓣蘭類的重要特徵：側萼片形成修長狀是捲瓣蘭核心物種的重要特徵，在台灣的豆蘭中，這種特徵演化在3個分子標記建構的演化樹都一致。而針對3群種內變異的分析顯示產於南投的長萼片型白毛捲瓣蘭其核酸變異程度較大，而花蓮捲瓣蘭變異族群因為核酸差異非常小故仍以花蓮捲瓣蘭視之，長軸捲瓣蘭的天池變異族群，在核酸變異度上也未有非常明顯的變異。而本實驗對三種葉綠體分子標記的結果顯示，matK較不適合探討台灣產豆蘭屬的關係，因其變異度較低，對豆蘭屬譜系分析的解析度不高，相較之下，trnC-rpoB IGS與trnL-trnF IGS較適合。

The genus Bulbophyllum is the largest taxon in Orchidaceae and there are nearly 2000 species distributed in the pantropical region. There were 21 species documented in the Flora of Taiwan second edition, and several new Bulbophyllum taxa were described afterwards and currently there are 23 species and 7 varieties recorded in Taiwan. This study analyzed 28 Bulbophyllum taxa from Taiwan and 10 others from Southeast Asia. Three chloroplast DNA molecular markers were examined in this study: matK partial sequence, trnC-rpoB intergenic spacer and trnL-trnF intergenic spacer partial sequence. Phylogenetic analysis was perfomed using maximum parsimony, neighbor-joining and Bayesian inference. Morphological character evolution was examined on the molecular phylogenies. Three different chloroplast DNA markers show similar pattern: solitary inflorescence group were at the basal position (especially the group without pseudobulb). Section Cirrhopetalum (lateral sepals longer than dorsal sepal, usually umbellate inflorescence) formed a core group, separated from those with shorter lateral sepals. Intraspecific studies of molecular phylogenetics from B. albociliatum、B. hirundinis and B. elecrtinum were perfomed. The result show that a Nantou sample of B. albociliatum var. albociliatum with a larger variation in nucleotide sequence. The result of three chloroplast markers used in this study show matK region is not a suitable marker in Bulbophyllum in Taiwan, because of its low sequence variation and problematic phylogenetic relationship of B. affine and B. macraei. New molecular markers are needed for phylogenetic studies of Bulbophyllum in the future.