臺灣鬚鱲 (鯉形目: 鯉科) 的親緣地理及形態變異之研究

Phylogeography and Morphological Variation of Candidia barbatus (Cypriniformes: Cyprinidae) in Taiwan Rivers

王 晨 帆(Chen-Fan Wang)

指導教授 ： 于宏燦

國立臺灣大學/生命科學院/動物學研究研究所/碩士(2005年)

https://doi.org/10.6342/NTU.2005.01291

摘要

中文摘要

本研究以粒線體細胞色素 b 基因序列作為分子遺傳標誌，試圖瞭解目前臺灣鬚鱲族群的遺傳多樣性、族群間基因交流的程度和可能的族群結構。並利用其結果整合相關的地質事件探討臺灣初級性淡水魚類相之起源模式。我採集自臺灣西部及東北部21條河川的26個樣點，總計337隻個體，並定序粒線體基因組細胞色素 b 基因序列（全長1140 bp）。所有的序列可歸納出23型haplotype (H01-H23)。以最大簡約法（Maximum parsimony，MP)，最大相似法（Maximum likelihood，ML)，貝氏分析（Bayesian inference，BI）和鄰聚法（Neighbor-joining，NJ) 4種方法所重建的親緣關係樹，皆支持將23型haplotype區分成6群不同的系群，分別是 Candidia lineages A~F。系群間的遺傳分化程度相當大，顯示臺灣鬚鱲可能存在不同的隱蔽種。依據分子鐘估計系群間的分歧年代，我推測這六群系群分歧的地點應該在中國大陸，而後陸續藉由更新世內不同的冰期多次入侵至臺灣。由於F系群內haplotype數量明顯多於其他系群，故F系群很可能是最早入侵臺灣的系群。可能的播遷路徑應該侷限在過去臺灣海峽內非深海區（即無海底峽谷地形存在）的範圍內。

臺灣鬚鱲族群內的遺傳變異偏低，但族群間及不同地理區間確存在高度的遺傳分化。26個臺灣鬚鱲族群間的基因交流程度甚小（平均Fst = 0.76），範圍縮小至同一流域內的族群也是相同的現象。北臺灣的淡水河流域8個族群間平均的Fst = 0.44，現今南臺灣的高屏溪流域3個族群間平均的Fst = 0.93。分子變方分析（AMOVA, Analysis of Molecular Variance）結果指出臺灣鬚鱲的族群結構可分為北部、中部，南部（不包括隘寮溪）和屏東地區（包括隘寮溪）。

臺灣鬚鱲在形態上依側線鱗數和側線上鱗數的差異可區分為兩型，分別是北型（northern type，54-56，11-12；包括Candidia A~C系群）和南型（southern type，50-52，9-10；包括Candidia D~F系群）。由形態特徵並不能區別出特定的系群，系群間的形態變異以及是否有生殖隔離存在有待更深入之研究。

關鍵字

臺灣鬚鱲粒線體細胞色素 b ； 多次入侵 ； 海底峽谷 ； 更新世

並列摘要

Abstract

In the present study, I employed the mitochondrial cytochrome b (mtDNA cyt b) gene as a molecular marker to investigate the phylogeographical patterns and genetic diversity of Candidia barbatus in Taiwan. Integrating the geohistorical events with genetic differentiation within C. barbatus can provide an appropriate model to reconstruct the originating pattern of the primary freshwater ichthyofauna of Taiwan.

MtDNA cyt b sequences of 1140 bp in length were scored from 337 specimens collected from 26 localities covering 21 rivers in western Taiwan from among which 23 different haplotypes were identified. The maximum parsimony (MP), maximum likelihood (ML), neighbor-joining (NJ), and Bayesian inference (BI) revealed similar mtDNA cyt b genealogies designated as Candidia lineages A~F. The deep genetic divergences occurring among lineages A~F suggest that cryptic species may exist within C. barbatus. The approximate molecular dating among lineages A~F indicate differentiations between them occurring earlier on the Asian mainland with subsequent multiple invasions toward Taiwan via a land bridge in the shallow-water zone of the Taiwan Strait during several glacial periods of the Pleistocene (1.6~0.02 million years). Lineage F was probable the first settler of this kind of dispersal toward the southernmost part of Taiwan as evidenced by its possession of more haplotypes.

The low genetic variability within populations resulted in an extremely high genetic divergence between populations and between geographical regions. Moreover, this was associated with a relatively low gene flow among the 26 populations (average Fst = 0.76) or even within the same drainage (average Fst = 0.44 in the Danshui River drainage; average Fst = 0.93 in the Kaoping River drainage). AMOVA could subdivide the likely population structure of C. barbatus into northern, central, southern (excluding the Ailiao tributary), and Pingtung (including the Ailiao tributary) groups.

Pore lateral line scales and transverse scale rows can be used to separate C. barbatus into two morphs: the northern type designated as Candidia A~C, with respective scale formulae of 54-56 and 11-12, and the southern type of Candidia D~F with formulae of 50-52 and 9-10. The northern type is identical with that shown in the original description. In addition to scale counts, other morphological variants could not be used to distinguish Candidia lineages A~F. A more-detailed study of the morphology is necessary, and the“concept of reproductive isolation”should be borne in mind.

並列關鍵字

Candidia barbatus ； mtDNA cytochrome b ； multiple invasions ； Pleistocene

參考文獻

Chen I. S. and Fang L. S. (1999) The freshwater and estuarine fishes of Taiwan. National Museum of Marine Biology and Aquarium, Taiwan.

Huang, M. T. (2003) Population genetics analysis of Zacco in Taiwan: an application of microsatellite. Master Thesis. Institute of Zoology, National Taiwan University, Taipei, Taiwan. (in Chinese)

Alves M. J., Coelho H., Collares-Pereira M. J., and Coelho M. M. (2001) Mitochondrial DNA variation in the highly endangered cyprinid fish Anaecypris hispanica: importance for conservation. Heredity, 87, 463-473.

Avise, J. C. (2000) Phylogeography: the history and formation of species. Harvard University Press, Cambridge, MA.

Avise, J. C. (2004) Molecular markers, natural history and evolution, 2nd ed. Sinauer Associates, Sunderland MA.