臺灣產碎雪草屬植物之系統生物研究

A Biosystematic Study on Euphrasia L. (Scrophulariaceae) in Taiwan

吳明洲(Ming-Jou Wu)

指導教授 ： 黃增泉

國立臺灣大學/生命科學院/植物科學研究所/博士(2004年)

https://doi.org/10.6342/NTU.2004.10058

摘要

碎雪草屬 (Euphrasia) 是半寄生植物，約有170種，分佈於北半球、澳洲、南美洲等寒冷地區及東南亞之高山與亞高山地帶。臺灣之碎雪草屬植物大部分產於全省二、三千公尺以上之高山地區，僅少數出現在一千至二千公尺之山地，分佈地大致上為雪霸、太魯閣及玉山等國家公園所涵說C在不同種間，碎雪草屬植物之葉片、花冠、雄蕊、果實之形態均極相近，然而在同種內之葉片、苞片、表面被毛及花色等形態上的差異，又常受到環境及宿主的影響，在種的界定上，一直是分類上的難題。例如，在生長過程中，莖基部最先生長的葉片通常較狹小而且少鋸齒，後來再長出的葉片則較寛大且多鋸齒。由於它們屬於半寄生性，因此它們的大小及生長的速率尚且受到宿主的種類或宿主的有無的影響。
根據研究可引用之各種特徵，結果顯示花粉粒與種子外表形態之微細構造在各分類群間並無明顯差異。外部形態經由主成分(PCO)分析及不加權平均連結(UPGMA)結果，可將臺灣產本屬植物分為四群。子房內之胚珠數、子房長度、花冠下唇斑點分佈型及花之長寬比等特徵可用來辨識這些分類群。
臺灣產之碎雪草屬植物之染色體均為二倍體，數目為n=11。相較於往昔歐洲碎雪草之四倍體、澳洲之四倍體、六倍體及十至十四倍體及南美洲之八倍體之報導而言，屬於原始型，顯示臺灣產本屬植物屬於冰河時期孑遺植物的可能。
檢測24個族群676個個體同皿Q的遺傳變異，獲得四個多型性的等位脢，經由族群連結分析(PAA)與不加權平均連結(UPGMA)分析的結果發現，這四個多型性等位脢的變異對於種的界定並沒有幫助。
檢驗55個族群147個個體細胞核核醣體DNA之ITS序列中，約有三分之一(48個體)的序列其個別的核甘酸，在個體內具有多型性的變異。這種加成性核甘酸 (Nucleotide additivity)的證據，顯示臺灣產碎雪草植物分類群間雜交的可能性。
分子親緣關係樹採用最簡約法則(Maxmum parsimony)，分析由99個非雜交型個體所得到的14個基因單型(Haplotypes)，並以野菰(Aeginetia indica L.)、馬先蒿(Pedicularis verticillata L.)與非本地產六個碎雪草節(Section Euphrasia)植物為外群。結果顯示臺灣產碎雪草植物四個分類群之nrITS親緣關係樹為一單系群，親緣關係樹的三個支系和四個分類群並不一致，但與地理分佈有關。不同分類群個體具有相同的基因單型，可能是Ancient polymorphism所致。
推論臺灣產碎雪草植物族群歷史，是依據40個族群99個個體細胞核核醣體DNA之ITS非加成性核甘酸序列，並利用集結樹枝分析(Nested clade analysis, NCA)的方法。集結樹枝圖(Nested cladogram)結合了14個基因單型所製成。用來了解基因之裔系與地理分佈的關係。集結樹枝分析指出，目前碎雪草植物族群的遺傳分佈，是由發生在不同的集結層次的六個歷史分隔(Past fragmentation)事件以及一個遠距離拓殖(Long distance colonization)和一個鄰域的族群擴張(Contiguous range expansion)事件所造成。幾個不同層次的歷史分隔事件，隱喻過去曾有若干個避難所的存在。我們假設碎雪草植物可能在更新世或更早就出現在臺灣的高山，在較早的一次冰河退卻時，一個分隔事件使臺灣產碎雪草植物分為不同海抜高度的兩群。此後，冰河作用加劇，碎雪草族群同時向南或朝向低海拔擴張。隨著冰河再次的退卻，碎雪草族群又同時向北或朝向高海拔退縮。因之，目前碎雪草呈現出高山棲息島嶼的分佈型，可能是受到最近一次的歷史分隔事件所致。
等位脢的變異與細胞核核醣體DNA之ITS序列的證據說明臺灣產本屬植物可能都是同一種。然而，本論文根據外部形態之結果，依照Yeo (1978)對本屬植物分類處理的原則，維持先前臺灣產本屬植物之分類處理（Wu & Huang, 1998），亦即：南湖碎雪草(E. nankotaizanensis Yamam.)、太魯閣小米草(E. tarokoana Ohwi)、玉山小米草(E. transmorrisonensis Hayata) 和台灣碎雪草(E. transmorrisonensis Hayata var. durietziana T. C. Huang & M. J. Wu) 等四個分類群。

關鍵字

加成性核甘酸 ； 碎雪草屬 ； 玉山小米草 ； 南湖碎雪草 ； 太魯閣小米草 ； 台灣碎雪草

並列摘要

Euphrasia plants are hemiparasitic herbs comprised of 170 species and they are distributed throughout the cold regions of the northern hemisphere, Australia and South America. They also inhabit in the alpine or subalpine areas of tropical or subtropical Southeast Asia. In Taiwan, the plants grow on mountains at elevations above 2000 m, and only rarely grow at elevations between 1000 and 2000 m. The habits of Euphrasia in Taiwan are mainly distributed widely throughout Sheipa, Taroko, and Yushan national park region. The controversial taxonomy of Euphrasia is mostly due to the overall similarity among species, and some morphological polymorphisms at intraspecific level. The plants vary in leaf size and shape, but the lower leaves usually are smaller, narrower and less dentate during their development, whereas the upper leaves are larger, wider, and more dentate. The size and growth rate of the plants are also influenced by whether they have established on hosts, as well as by the host species.
Four groups/taxa are demonstrated in both principle coordinates analysis (PCO) and the unweighted pair-group method using arithmetic averages (UPGMA) based on morphological data. The ovule number per ovary, ovary length, spot distribution patterns on lower lip of the corona, and ratio of flower width to length can be used to distinguish these taxa.
The chromosome number was n=11, and all four taxa were diploids. The diploids are primitive compared with previous reports of tetraploids in Europe, tetraploids, hexaploids and 10-14 ploids in Australia, and octaploids in South America. Their primitiveness corresponds with the primitive state in the perennial section, which might imply that Taiwanese Euphrasia are relics.
Examining 676 individuals in 24 populations detected four polymorphic allozymes for genetic variation. No discrimination of these allozymes in the species boundary was found using population aggregation analysis (PAA) and UPGMA.
In the study of nuclear ribosomal ITS sequences, one-third (48) of 147 individuals in 55 populations have nucleotide additivity. It implies that hybridization occurred among Taiwanese Euphrasia taxa. A phylogenetic tree was reconstructed using maximum parsimony method based on 14 haplotypes of 99 nonadditivity individuals along with Aeginetia indica L., Pedicularis verticillata L., and six foreign Euphrasia of Section Euphrasia. The phylogenetic tree shows that four taxa of Taiwanese Euphrasia are monophyletic. Three lineages shown on the phylogenetic tree were not congruent with four taxa of Taiwanese Euphrasia, but did correlate with geographic distribution of the plants. It is inferred that individuals among different taxa shared the same haplotype due to ancient polymorphisms.
Using the nested clade analysis (NCA), the history of population of Taiwanese Euphrasia is inferred based on nrITS sequences of 99 nonadditivity individuals in 40 populations. A nested cladogram that combined 14 haplotypes was designed to discern the relationship between gene genealogy and geographical distribution. NCA implies that the current genetic distribution arose from six past fragmentation events that occurred at different nesting levels as well as one instance each of long distance colonization and contiguous range expansion. The several past fragmentation events at various nesting levels implied that several refuges previously existed. From the NCA, we postulated the following scenario of the population history of Taiwanese Euphrasia. At the beginning of or just before the Pleistocene era, Euphrasia settled in the mountainous areas of Taiwan. During an early glacial degeneration, a fragmentation event that probably occupied different elevations separated Euphrasia plants into two groups. Thereafter, by a glacial invasion, the distribution range of Euphrasia expanded toward southward at horizontal and upward at elevation. Subsequent fragmentation occurred during other glacial degenerations, and the population contracted toward northward at horizontal and upward at elevation. Therefore, populations of Euphrasia plants isolated by mountainous habitat-islands might have arisen from the most recent fragmentation event.
Allozyme variation and nrITS evidence suggested that Taiwanese Euphrasia plants are probably conspecies. However, taxonomic treatment based solely on morphology as in the case of classification of Euphrasia treated by Yeo (1978), we remains the taxonomic treatment proposed by Wu & Huang (1998) unchanged. The four taxa are: E. nankotaizanensis Yamam., E. tarokoana Ohwi, E. transmorrisonensis Hayata, and E. transmorrisonensis Hayata var. durietziana (Ohwi) T. C. Huang & M. J. Wu.

並列關鍵字

E. transmorrisonensis Hayata ； E. transmorrisonensis Hayata var. durietziana T. C ； E. tarokoana Ohwi ； E. nankotaizanensis Yamam. ； Euphrasia ； Nucleotide additivity

參考文獻

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