中文摘要

位於歐亞大陸邊緣的台灣島自形成後，許多物種從歐亞大陸播遷來台，主要生物相逐漸形成。棲息於島嶼的淡水魚類，是提供親緣地理研究的理想材料。鱨類Bagrus具有高度的形態多樣化並廣泛分布於亞洲，為適合研究生物地理學的一群。長期以來並無學者對台灣產鱨類的分子親緣關係做進一步的研究。
依外部型態之差異，可將台灣產鱨類分為兩群：（1）短臀擬鱨Pseudobagrus brevianalis與台灣擬鱨P. taiwanensis類群；（2）長脂擬鱨P. adiposalis。本研究用這兩類群，以PCR增幅粒線體DNA內變異速率最快的D-loop片段，結合傳統與現今分子演化探討其族群遺傳結構與地理親緣關係，並且釐清短臀擬鱨與台灣擬鱨的關係。
不論外部分類特徵或是分子遺傳證據都無法證明短臀擬鱨與台灣擬鱨同時存在。台灣產鱨類侷限在台灣西部的地理分布形態與中央山脈隆起造成的隔離有高度相關。依據親緣關係樹，這兩種擬鱨以苗栗丘陵為界，各自分為北部群與中部群兩個分群。不論是族群內或族群間，這兩種擬鱨的粒線體D-loop序列的歧異度都不是非常高，短臀擬鱨有10種基因型，遺傳距離為0.1%~1.6%，長脂擬鱨有三種基因型，遺傳距離為0.3% ~1.8%。
從分子的證據上顯示，本島現生的鱨類應存在兩種明顯有效種--短臀擬鱨與長脂擬鱨，雖然在形態上不足以說明短臀擬鱨與長脂擬鱨各自的分群是不同種，但每一種之不同地理區之間的遺傳距離相當明顯，因此可能是在亞種的階層。

Abstract

Taiwan island locates at the margin of Eurasia plate. Lots of species have dispersed from the mainland of Eurasia to Taiwan after the formation of the island. The main biota of Taiwan has formed consequently. Freshwater fishes dwelling in island-like habitats provide an ideal model for phylogeographical studies. Bagrids are an attractive group because of a great morphological diversity and wide distribution. But only a few studies focused on the phylogenetic relationships of Taiwan bagrids.
Based on the comparisons of their morphological characters, this group of fishes can be divide into two groups: (1) Pseudobagrus brevianalis and P. taiwanensis; (2) P. adiposalis . The aim of our present work are to sequence D-loop of thses two groups and then to analyse population genetic structures and the phylogeographical patterns and the relationships of P. brevianalis and P. taiwanensis.
No matter the morphological characters or genetic evidence can’t prove that P. brevianalis and P. taiwanensis are both existed . The biogeographical pattern of bagrid catfishes in Taiwan, with a distribution range restricted to western Taiwan, is highly correlated with the topographical isolation by the Central Mountain Range. According to the phylogenetic tree, the populations of the two species demarcated by Miaoli Plateau and fell into two clusters: (1) the northern group; (2) the central group. Genetic variability in the mitochondrial control region of the bagrid catfishes in Taiwan examined was low at both within- and among- population levels. P. brevianalis has ten haplotypes and the genetic distance is from 0.1% to 1.6%, and P. adiposalis has three haplotypes and the genetic distance is from 0.3% to 1.8%. According to the previous studies and this work, the low variability in bagrids should be explainable by some historical biogeographic reason or molecular evolutionary rate . Genetic distance between northern population and middle population is high, although the morphological characters are quiet similar. The results suggest northern population and middle population are possible subspecies.

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