台灣產堇菜屬多倍體物種演化與起源
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2013
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雜交與多倍體化為植物界中常見的種化機制，由這兩種機制所產生的新物種會帶有更高的基因歧異度，並將物種帶往新的適應高峰。堇菜屬(Viola, Violaceae)植物是研究植物演化的重要材料之一，屬內物種在雜交及倍體數上的變化長期以來十分受到學者的關注。台灣產堇菜屬植物中，以蔓莖群(Diffusae)和合生托葉群(Adnatae)的染色體數目變化最引人注目。在蔓莖群中的四個物種其染色體為n=13 （茶匙黃）、24 （台北堇菜、普萊氏堇菜）、37 （心葉茶匙黃），合生托葉群內四個物種的染色體數則是n=12 （短毛堇菜）、24（小堇菜、紫花地丁）、36 （箭葉堇菜），兩群中染色體數皆呈倍數增加，雖然早有學者推論六倍體物種是由二倍體和四倍體物種雜交而來，卻遲遲未被證實。本研究利用母系遺傳的葉綠體DNA序列片段(trnL/trnF、rpl16)及核DNA序列片段(ITS)進行分析，加上鄰近地區樣本之序列，以最大簡約法與貝葉氏導出式分析重建台灣產堇菜屬蔓莖群與合生托葉群的演化歷史。
根據葉綠體DNA序列所建立的親緣關係樹，蔓莖群中的台北堇菜自成一支，與其他蔓莖群的物種關係較遠，合生托葉群的物種則是聚成支持度高的一群。在核DNA序列的部份，因多倍體物種多有同源基因拷貝，在親緣關係樹上呈現較複雜的表現，蔓莖群中的心葉茶匙黃分別與茶匙黃、台北堇菜和普萊氏堇菜、合生托葉群四倍體物種各自形成具三個具有支持度的分支；合生托葉群的箭葉堇菜則分別和短毛堇菜、小堇菜、紫花地丁各自形成多個具支持度的分支。
依據研究結果推論心葉茶匙黃是由茶匙黃或其近緣種、與台北堇菜和普萊氏堇菜共有的二倍體祖先、以及與合生托葉群共有的二倍體祖先等三個親本經兩次雜交及多倍體化而來。箭葉堇菜則可能是由短毛堇菜或其近緣種、長萼堇菜或其近緣種和與紫花地丁、早開堇菜共有的二倍體祖先雜交形成的。
Hybridization and polyploidization are common mechanisms in plant speciation. Via these mechanisms, the new lineages often can get higher genetic diversity than their parents and reach new adaptive peaks. Violets (Viola, Violaceae) are used as a material for plant evolution process, particularly focus on the ploidy level. In Taiwan, Viola group Diffusae and group Adnatae have very special cytological situation. The chromosome numbers in group Diffusae are n=13 (V. diffusa), 24 (V. nagasawai var. nagasawai and V. nagasawai var. pricei), 37 (V. tenuis), and the chromosome numbers in group Adnatae are n=12 (V. confusa), 24 (V. mandshuica and V. inconspicua subsp. nagasakiensis), 36 (V. betonicifolia), both of them increase as polyploidy. Early studies inferred that the hexaploid may be derived from hybridization and subsequent polyploidization between diploidy and tetraploidy ancestors which in the same group, but none of them be tested. This study used cpDNA (trnL/trnF, rpl16) and nrDNA (ITS) and be analyzed by maximum parsimony analysis (MP) and Bayesian inference analysis (BI) to reconstruct the relationship within these two polyploidy complex. Based on the phylogeny tree of cpDNA, group Adnatae and group Diffusae were grouped separately in two well-supported clades but V. nagasawai var. nagasawai was not included. The nrDNA phylogeny tree showed that V. teunis nests in three different clades: V. diffusa, V. nagasawai var. nagasawai and V. nagasawai var. pricei, and the species of group Adnatae. Viola betonicifolia was separated to several different clades and gathered with V. mandshuica or V. inconspicua subsp. nagasakiensis. The results indicated that V. teunis have three different parental species, one is V. diffusa or closely related species, another is a unknown diploid which shares a genome with V. nagasawai var. nagasawai and V. nagasawai var. pricei, and the last one is another unknown diploid which were shared with group Adnatae. Viola betonicifolia maybe a hybrid between V. confuse or closely related species, V. incospicua or closely related species and a diploid which were shared with V. mandshuica and V. prionantha.
Hybridization and polyploidization are common mechanisms in plant speciation. Via these mechanisms, the new lineages often can get higher genetic diversity than their parents and reach new adaptive peaks. Violets (Viola, Violaceae) are used as a material for plant evolution process, particularly focus on the ploidy level. In Taiwan, Viola group Diffusae and group Adnatae have very special cytological situation. The chromosome numbers in group Diffusae are n=13 (V. diffusa), 24 (V. nagasawai var. nagasawai and V. nagasawai var. pricei), 37 (V. tenuis), and the chromosome numbers in group Adnatae are n=12 (V. confusa), 24 (V. mandshuica and V. inconspicua subsp. nagasakiensis), 36 (V. betonicifolia), both of them increase as polyploidy. Early studies inferred that the hexaploid may be derived from hybridization and subsequent polyploidization between diploidy and tetraploidy ancestors which in the same group, but none of them be tested. This study used cpDNA (trnL/trnF, rpl16) and nrDNA (ITS) and be analyzed by maximum parsimony analysis (MP) and Bayesian inference analysis (BI) to reconstruct the relationship within these two polyploidy complex. Based on the phylogeny tree of cpDNA, group Adnatae and group Diffusae were grouped separately in two well-supported clades but V. nagasawai var. nagasawai was not included. The nrDNA phylogeny tree showed that V. teunis nests in three different clades: V. diffusa, V. nagasawai var. nagasawai and V. nagasawai var. pricei, and the species of group Adnatae. Viola betonicifolia was separated to several different clades and gathered with V. mandshuica or V. inconspicua subsp. nagasakiensis. The results indicated that V. teunis have three different parental species, one is V. diffusa or closely related species, another is a unknown diploid which shares a genome with V. nagasawai var. nagasawai and V. nagasawai var. pricei, and the last one is another unknown diploid which were shared with group Adnatae. Viola betonicifolia maybe a hybrid between V. confuse or closely related species, V. incospicua or closely related species and a diploid which were shared with V. mandshuica and V. prionantha.
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Keywords
堇菜屬, 多倍體化, 雜交, trnL/trnF, rpl16, ITS, Viola, hybridization, polyploidization, trnL/trnF, rpl16, ITS