本研究藉由分析核糖體核酸(ribosomal DNA,rDNA)內轉錄間隔區(internal transcribed spacer,ITS)之序列,以探討台灣20種原生杜鵑的親緣關係。將20種台灣原生杜鵑的ITS序列進行比較排列後發現,在ITS1區域有37個變異處,在ITS2區域有35個變異處。以Kimura 2-parameters換算物種兩兩間的遺傳距離(genetic distance),發現這20種杜鵑間的遺傳距離介於0-0.062間。經不加權平均重法(unweighted pair-group methodanalysis,UPGMA)進行群叢分析,並完成親緣關係樹狀圖(phylogenetic tree)。根據樹狀圖所呈現之物種間的親緣關係,台灣的原生杜鵑主要可以分成六群,其中埔里杜鵑(R. lasiostylum)、紅毛杜鵑(R. rubropilosum)、烏來杜鵑(R. kanehirai)、南澳杜鵑(R. breviperulatum)、金毛杜鵑(R. oldhamii)、細葉杜鵑(R. noriakianum)、中原氏杜鵑(R. nakaharai)、台灣高山杜鵑(R. taiwanalpinum)、大屯杜鵑(R. longiperulatum)與唐杜鵑(R. simsii)歸於第一群;長卵葉馬銀花(R. lamprophyllum)與馬銀花(R. ovatum)歸在第二群;南湖杜鵑(R. hyperythrum)、森氏杜鵑(R. morri)、台灣杜鵑(R. formosanum)及玉山杜鵑(R. pseudochrysanthum)與紅星杜鵑(R. rubropunctatum)歸在第三群。此外,西施花、黃花杜鵑及守城滿山紅則分別自成一群。上述ITS序列所得的親緣關係與目前台灣原生杜鵑所歸屬的系統分類進一步比較,發現在亞屬及節的層次皆很相符。
Genetic relationship of 20 Rhododendron species in Taiwan was derived based on the sequence analysis of the internal transcribed spacer (ITS) region of ribosomal DNA. Sequences of complete ITS region, including ITS1, 5.8S rDNA, and ITS2, were obtained by direct sequencing of polymerase chain reaction (PCR) amplified fragments. Gaultheria itoana was used as outgroup. Aligned sequences of ITS1 and ITS2 from 21 taxa resulted in 493 characters. According to the dendrogram, six main clusters were generated among 20 species of genus Rhododendon in Taiwan. R. hyperythrum, R. morri, R. formosanum, and R. pseudochrysanthum are grouped with R. rubropunctatum; R. lamprophyllum are grouped with R. ovatum; R. lasiostylum, R. rubropilosum, R. kanehirai, R. breviperulatum, R. oldhamii, R. noriakianum, R. nakaharai, R. taiwanalpinum, and R. longiperulatum are grouped with R. simsii. In addition, R. kawakamii, R. ellipticum and R. mariesii are three independent clusters. Molecular data from ITS sequences in the present study is in agreement with traditional systematics of Rhododendron.