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Relationship between population genetic structure and riparian habitat as revealed by ISSR analysis of the rheophyte Acorus gramineus Soland. (Araceae) in Taiwan.
|摘要:||石菖蒲（Acorus gramineus Soland.）是臺灣原生的溪流植物之一，為天南星科（Araceae）的多年生宿根草本，分布在臺灣全島中低海拔約200∼2000公尺的河岸岩石上，因其族群局限在溪流環境內，呈現不連續的分布，基因流在不同水系間的交流機會較少，不同溪流間的族群遺傳結構可能會有較大的差異。ISSR是在串聯短重複序列SSR的3''或5''端，加上一至四個核酸後做為引子進行聚合連鎖反應，放大SSRs之間的序列，此方法具有RAPD省時省力花費較少等等的優點，但能得到比RAPD程度更高的多型性資料；目前關於以ISSR做為分子標記的報告多以栽培種為材料，以天然族群為研究材料的報告極少。本文使用ISSR研究臺灣西部六條溪流的石菖蒲族群遺傳結構，共採集十七個族群、255個樣本，採用六個ISSR引子，分析ISSR引子所放大的78條多型性條帶的變異。AMOVA分析的結果，在所有變方成分中，水系間變方成分佔36.86%，水系內族群間變方成分佔21.26%，族群內變方成分佔41.88%，顯示石菖蒲的族群在溪流間確有明顯的分化，水系內族群間的分化較少但仍然顯著；歸群以及主座標分析的結果，大致上依緯度分成兩大群，但大甲溪與其他水系的族群關係較遠，儘管如此，在主座標圖中，大甲溪與中南部的族群仍比與北部族群的關係近。|
Acorus gramineus Soland. (Araceae) is a native rheophyte in Taiwan. It is a perennial herbaceous plant and generally found on rocks and cliffs along river banks at the altitude from 200 to 2000 m. The distribution of the species is limited to the riparian habitat and thus discontinuous in pattern. The gene flow is therefore suspected to be restricted mainly within the same river system and we hypothesize that plants of different river systems might have rather distinct genetic structure due to limited gene flow among them. ISSR is a molecular marker using a few copies of short sequence repeat added with one to four nucleotides at the 3'' or 5'' end as a primer to amplified the sections between two SSRs in the genomic DNA. The method has the advantage of simplicity as RAPD but may produce more polymorphic information then RAPD. ISSR has been employed in some studies of cultivated plants and few studies of natural populations. In the present study, 255 individual samples from 17 sampling sites (populations) in six river systems were studied using ISSR markers. The variation of 78 polymorphic ISSR bands in the samples were recorded. The analysis of molecular variance (AMOVA) revealed that the variance components among river systems, among populations within river systems, among individuals within populations were 36.86%, 21.26%, and 41.88% of the total variance, respectively. The result indicated that there is a considerable genetic diversification among river systems. The diversification among populations within river systems is smaller but significant. The cluster analysis and principal coordinate analysis revealed two major general groupings of northern and central-southern groups. The river system Dagiashi was found to be a relatively isolated group by the cluster analysis. However, the result of principal coordinate analysis indicated that the river system Dagiashi was closer to the central-southern group.
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