臺灣鮭魚(Oncorhynchus masou formosanus)的遺傳多樣性

Abstract

連續兩年( 2004 和2005 年) 使用擴增片段長度多樣性(Amplified Fragment Length Polymorphism ;簡稱AFLP)分子標記技術調查七家灣溪流域野生臺灣鱷魚、(Oncorhynchus masou formosanus)族群的遺傳多樣性。從58個樣本中擴增出196 個條帶， 其中多樣性條帶有58 條(29.59%) ，族群的遺傳多樣性指數(He)為0 . 0 5 7 '相似系數( Similarity values)為0.9692，平均遺傳距離(D)為0.0312，顯示臺灣鮭魚、族群極端缺乏遺傳變異， 而且族群擁有的稀有對偶基因也快速消失。以UPGMA 及NJ 法構建的歸類圖， 顯現七家灣溪流域的野生臺灣鮭魚是由三個主要的系群(clade)構成， 並以此維繫遺傳多樣性。我們推測臺灣鮭魚因應時空地理而分布，並以多樣化的行為模式產生關聯族群的現象。然而人類的開發不但改變野生鮭魚族群之大小、數目與組成，同時也瓦解關聯族群之結構和聯繫。保持各地域族群的暢通，重建野生臺灣鮭魚關聯族群之結構，可以減緩野生臺灣鮭魚遺傳多樣性的流失。We examined the genetic diversity of 58 wild Formosa landlocked salmon in Chichiawan Stream using AFLP(Amplified Fragment Length Polymorphism) markers for two consecutive years (2004 and 2005). One hundred and ninety six bands were detected using 3 primer pairs, of which 58 were polymorphic with a proportion of 29.59%. The population has a low genetic diversity (He = 0.057) with averagesimilarity values 0.9692 and average genetic distance0.0312, respectively. The rare alleles also disappeared rapidly. Both UPGMA and NJ dendrograms indicated the studied individuals can be divided into three main clades. The study of genetic variation of AFLP indicates a strong pattern of spatial and geographic structuring in the existing Formosa landlocked salmon. We hypothesize that Formosa landlocked salmon populations that existed historically in the mainstem of the Tachia River may have formed core populations for regional metapopulations. Human development has altered the organization of salmon populations , and consequently has changed metapopulation organization. Diversity within and among salmon populations has been substantially reduced due to the extinction of many local populations, as well as a reduction in population size of most extant populations. Re-establishment of metapopulation structure among Chichiawan Stream salmon populations would function to slow the loss of diversity in the presently isolated populations.