台灣高山六倍體蠅子草屬植物之起源與演化

The origin and evolution of alpine hexaploid Silene in Taiwan

施福隆(Fu-Lung Shih)

指導教授 ： 王震哲

國立臺灣師範大學/理學院/生命科學研究所/碩士(2012年)

摘要

分佈於台灣高海拔山區的三種蠅子草屬特有種植物，分別是玉山蠅子草（Silene morrisonmontana var. morrisonmontana）、禿玉山蠅子草（S. morrisonmontana var. glabella）及蓬萊蠅子草（S. formosamotana），此三者形態相似且部分基因片段有相同之單套型故合稱為玉山蠅子草複合群。此三種均為六倍體，根據分佈地點及形態特徵推估其起源親本可能是：一、亦分佈於台灣的四倍體近緣種女蔞菜（S. aprica）和堅硬女蔞菜（S. firma）；二、形態相似且同屬玉山蠅子草組（sect. morrisonmontanae）的湖北蠅子草（S. hupehensis），柳葉蠅子草（S. salicifolia）及劍門蠅子草（S. tubiformis）；但若玉山蠅子草複合群是在台灣島外或是經由異源多倍體化而形成，則其起源親本亦有可能會是其他的物種。本研究利用實際採集於台灣的材料及下載自基因庫裡親緣相近類群的序列資料，以三個葉綠體基因片段（matK、rps16和psbE到petL之中間片段）及兩個核內基因片段（RPD2a和RPD2b）為分子標記，透過分子親緣樹的建構及親緣地理的分析來釐清玉山蠅子草複合群的起源親本，並推測其起源可能的時間與空間背景。
本研究結果顯示五個基因片段在玉山蠅子草複合群的三個物種間存在數個相同的單套型，且所得之單套型在分子親緣樹中都同位於一個中度到高度支持的支序上，由此可以確認玉山蠅子草複合群是由單一起源事件而來，推估是晚近才分化成現今三個形態有所差異的物種；而兩個核內基因片段的單套型則各自皆落在兩個不同的支序上，故可得知玉山蠅子草複合群是由不同類群雜交而來的異源多倍體。結果中不論島內分佈的女蔞菜、堅硬女蔞菜，還是形態分類上同組的湖北蠅子草及柳葉蠅子草，其單套型在五個基因片段的親緣樹裡皆位於與玉山蠅子草複合群不同之高度支持的支序上，顯示上述四個物種都不是玉山蠅子草複合群的親本物種。
在與玉山蠅子草複合群處於同一支序的類群中，並未發現有完全吻合之較低倍體數的親本物種，推測其可能已經滅絕或是未在本次研究的採樣類群之中，雖則在rps16和psbE/petL中間序列結合片段的結果中，囊謙蠅子草（S. nangqenensis）有可能是玉山蠅子草複合群的母系親本，但因缺乏其核內基因及倍體數的資料故無法進一步確認；無論是從葉綠體基因片段或是核內基因片段其中一型，都可發現玉山蠅子草複合群的母系親本近緣種大多分佈在青藏高原，而其父系親本近緣種在RPD2a的結果中則大多分佈在東北亞，故其起源可能是透過這兩地物種族群的雜交多倍體化而來；另外可能是異源四倍體的喜馬拉雅蠅子草（S. himalayensis）推估應是玉山蠅子草複合群同母異父的姐妹種，而玉山蠅子草複合群的母系親本則可能是應為異源四倍體的隱瓣蠅子草（S. gonosperma）之父系親本。

關鍵字

異源多倍體 ； 分子親緣樹 ； 親緣地理 ； 玉山蠅子草複合群

並列摘要

Three endemic Silene species distributed on high-altitude mountains in Taiwan re-spectively are S. morrisonmontana var. morrisonmontana, S. morrisonmontana var. glabella and S. formosamotana. Together they were called S. morrisonmontana complex for having similar morphological traits and same haplotypes of some gene regions, and are all hexaploids. According to geographical distribution and morphological characters, their origin species possibly are: (1). The phylogenic-closed tetraploids S. aprica and S. firma which also distributed in Taiwan, (2). The companion species S. hupehensis, S. salicifolia and S. tubiformis of sect. morrisonmontanae. But if S. morrisonmontana complex were formed out of Taiwan or through allopolyploidy, then their source would rather be the other species. In this study, we use three chloroplast (matK, rps16 and psbE to petL intron) and two nuclear (RPD2a and RPD2b ) gene regions as molecular markers. The sequence data were obtained both from materials collected in Taiwan and GenBank. We wished to clarify the origin of S. morrisonmontana complex and estimate the possible temporal and special background of it by the construction of phylogeny tree and phylogeographic analysis.
The results showed three species of S. morrisonmontana complex shared same hap-lotypes in all five gene regions, and those were all respectively grouped in high-ly-supported clade. Base on it, S. morrisonmontana complex are estimated to have a single origin, and differentiated into three species recently. Also, the haplotypes of two nuclear gene regions were grouped into two different clades respectively sugessested S. morrisonmontana complex are allopolyploids. Neither S. aprica, S. firma nor S. hupe-hensis, S. salicifolia are the origin species, because their haplotypes of five gene regions were all in the different highly-supported clades with S. morrisonmontana complex.
There was no species with lower ploid-level completely fit in the same clade with S. morrisonmontana complex, suggesting that the origin species may be extinct or not in-cluded in this study. Thought S. nangqenensis could possibly be the maternal origin base on the result of rps16 and psbE/petL intron combined sequence, but still unsolved for the lack of nuclear genes and ploidy information. Whether chloroplast or nuclear markers showed that the most closed species of maternal origin were distributeted in the Qinghai-Tibet Plateau, and of paternal origin were in Northeast Asia based on the result of RPD2a region. Infer from this, S. morrisonmontana complex might derive from the hybridization between two geographic-distinct species when they encounter each other. Moreover, S. himalayensis shared with S. morrisonmontana complex the same maternal origin which also could be the paternal origin of S. gonosperma.

並列關鍵字

Allopolyploid ； phylogeny ； phylogeography ； Silene morrisonmontana

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