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題 名 | Strong Incongruence between the ITS Phylogeny and Generic Delimitation in the Nemosenecio-Sinosenecio-Tephroseris Assemblage (Asteraceae : Senecioneae)=狗舌草亞族複合群 (菊科 : 千里光族) 的屬間界限與 ITS 分子證據的衝突 |
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作 者 | 王留陽; 劉建全; |
書刊名 | Botanical Studies |
卷 期 | 50:4 2009.10[民98.10] |
頁 次 | 頁435-442 |
分類號 | 377.2215 |
關鍵詞 | 菊科; 款東亞族; 華千里光屬; 狗舌草屬; 羽葉千里光屬; 分子系統發育; 核糖ITS區域; Asteraceae; Internal transcribed spacer region; ITS region; Nemosenecio; Molecular phylogeny; Sinosenecio; Tephroseris; Tussilagininae; |
語 文 | 英文(English) |
中文摘要 | 傳統菊科千里光族狗舌草亞族主要包括狗舌草屬、華千里光屬和羽葉千里光屬三屬,這裏我們暫稱為“狗舌草亞族複合群”。目前這三個屬的親緣關係和系統位置存在較大分歧,需要進一步修訂。在本研究中,我們新報導了13 個種的19 條核糖體內轉錄間隔區ITS 序列;並結合Genbank 已報導序列,對該複合群27 個種(覆蓋了這三個屬所有的組和亞組)和款東亞族內近緣屬的7 個代表種的核糖體內轉錄間隔區ITS 構建了分子系統發育樹。研究發現華千里光屬和狗舌草屬均非單系起源。華千里光屬四個種,包括該屬的模式種(S. eriopodus, S. hederifolius, S. homogyniphyllus 和 S. subcoriaceus)與橐吾屬、垂頭菊屬和蟹甲草屬等近緣屬的代表種聚為一支,即分支B,但支援率不高;而該屬其他10 個代表種則與狗舌草屬的13 個種和羽葉千里光屬的3 個種共同組成分支A,並得到較高的自展支持。主要分支A 含有兩個穩定的亞分支C 和D:其中亞分支C 包括狗舌草屬的10 個種與華千里光屬的兩個種S. newcombei 和 S. koreanus ,而亞分支D 包括了所有三個屬的其他11 個種。另外,亞分支D 內,T. changii 與華千里光屬的4 個代表種聚為一支,而羽葉千里光屬的3 個代表種則單獨組成一個單系分支。結合先前的有關外部宏觀和微觀性狀特徵的研究與本研究中的ITS 分子證據,這三個屬的屬間界限需要進行適當調整:S. newcombei 和 S. koreanus 兩個種應放在狗舌草屬內;而華千里光屬也應包括本研究中分支B 內一些近緣屬的代表種;本研究所涉及到華千里光屬和T. changii 應歸併至羽葉千里光屬,或成立一個新屬。但無論如何,這三個屬間界限仍需要更多形態學和分子證據,需要進一步的調查和研究。 |
英文摘要 | The three genera Sinosenecio, Nemosenecio and Tephroseris form a closely knit group nested in the subtribe Tussilagininae of the tribe Senecioneae (Asteraceae). The generic limits in this assemblage remain unclear and need revision. In this study, we analysed sequences of the internal transcribed spacer (ITS) region of nuclear ribosomal DNA available from GenBank and sequenced 19 accessions of an additional 13 species encompassing all three genera. Phylogenetic analyses based on the ITS variation of 27 species in this assemblage and seven species from related genera of the Tussilagininae suggested that neither Sinosenecio nor Tephroseris is monophyletic. The sampled species of Sinosenecio were scattered in different clades or subclades of the phylogenetic tree. Four species of this genus, including the generic type species (S. eriopodus, S. hederifolius, S. homogyniphyllus and S. subcoriaceus) are clustered in a tentative clade with genera such as Ligularia, Cremanthodium, Parasenecio, Farfugium and Tussilago. The remaining ten Sinosenecio species comprise a highly supported clade together with 13 Tephroseris species and four Nemosenecio species. Within this clade, 10 Tephroseris species together with two Sinosenecio species (S. newcombei and S. koreanus) comprise a monophyletic subclade while the remaining 11 species from all of three genera are clustered into another clade with moderate statistical support. Within the latter subclade, T. changii was revealed to be closely related to four Sinosenecio species, and three Nemosenecio species comprising a monophyletic lineage. These two lineages form a polytomous radiation with the other two Sinosenecio lineages. The generic delimitations of the three genera clearly need some adjustments, which is also supported by previous studies of gross and floral morphology. Two Sinosenecio species (S. newcombei and S. koreanus) should be transferred to Tephroseris, and the genus Sinosenecio should be re-circumscribed to contain those species clustered in the Ligularia—Tussilago clade. Most of the other described species under Sinosenecio and T. changii should either be transferred to an enlarged Nemosenecio concept, or a new genus needs to be established to encompass them. However, the morphological distinctions between these genera require further investigation. |