台灣小鰾鮈屬粒線體基因與核基因的比較親緣地理學

Incongrunt phylogeographic patterns between mtDNA and nuclear markers in the genus Microphysogobio in Taiwan

吳庭瑜(Ting-Yu Wu)

指導教授 ： 王弘毅

國立臺灣大學/生命科學院/生態學與演化生物學研究所/碩士(2018年)

https://doi.org/10.6342/NTU201803217

摘要

由於生物有限的擴散能力及拓遷歷史，淡水魚類是研究親緣地理的良好物種。過去台灣淡水魚的親緣地理研究，常以地理隔離解釋族群分化，然而有時地理障壁建立所造成的族群分隔無法完全解釋不同物種在不同時間分化的情形，族群分化的機制除了地理隔離以外是否有其他可能成因尚待釐清。小鰾鮈屬 (Microphysogobio) 在分類上為鯉科 (Cyprinidae) 鮈亞科 (Gobioninae) ，是原生在東亞的小型淡水魚，目前確定發表的物種有 26 種，其中高身小鰾鮈 (M. alticorpus，MA) 與短吻小鰾鮈 (M. brevirostris，MB) 是台灣特有種，異域分布在苗栗以北及以南。本研究以粒線體 cytb 基因與 8 種核基因序列作為 2 組分子標記，揭示兩物種種內的族群結構與分化歷史，結果兩物種的種內族群分化顯示出不同模式。高身小鰾鮈在粒線體序列時呈現兩獨立支系群，在核基因序列時族群有基因交流，粒線體與核基因呈現族群分化不一致的原因可能是粒線體受到天擇影響，保育層面，演化顯著單位 (ESU) 可能需要重新省視；短吻小鰾鮈在粒線體與核基因序列的族群分化情形較為一致，可分成兩主要支系群，距今約 0.14 百萬年前，可能發生過族群擴張，保育上應注重兩支系群的相異遺傳特性。本研究的重要性為第一次以分子證據證實高身小鰾鮈與短吻小鰾鮈在後龍溪共域分布；也呈現出粒線體基因可能並非中性的分子標記，可能受到天擇壓力，影響族群分化。

關鍵字

小鰾鮈屬 ； 親緣地理 ； 天擇 ； 粒線體 DNA

並列摘要

Freshwater fishes are ideal model species for studying phylogeographical patterns due to their limited dispersal capabilities and colonization histories. In the previous studies, vicariance events are often considered as the causes of population differentiation. However, this can not completely present the history of population differentiation, especially for differentiation of different species in different time. The mechanism of differentation in populations is still debating. Microphysogobio is a genus of small-sized freshwater fishes, belonging to the cyprinid subfamily Gobioninae distributed in East Asia. Twenty six species of Microphysogobio are considered valid in the world, and two species of which, M. alticorpus (MA) and M. brevirostris (MB) , are endemic to Taiwan. They are allopatrically distributed in, north and south of the Miaoli Plateau, respectively. In this study, I employed the mt cytb gene and eight nuclear genes as molecular markers to unravel the colonization and divergent histories of these two species. The results showed that there were different patterns of intraspecific differentiation in these two species. In MA, mt cytb revealed distinct lineages for samples collected from different localities. The nuclear genes, however, clearly showed gene flow between distinct mtDNA defined lineages. The mito-nuclear discordance may be caused by selection in mitochondrial genome. For conservation, evolutionarily significant units (ESU) should be rechecked. In MB, mtDNA and nuclear genes revealed two major lineages, and there may be population expansion in 0.14 million years ago. Different genetic basis of two lineages should be considered for conservation. The importance of this study is presenting molecular evidence of MA and MB were sympatric in Houlung river. Furthermore, the study suggested mitochondrial genome may not be neutral, and it may reveal signature of selection, which affected differentiation of populations.

並列關鍵字

Microphysogobio ； phylogeography ； selection ； mtDNA

參考文獻

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