长江流域两种新银鱼分子生态学初步研究

【作者】 史洁蔷；

【导师】 王忠锁；

【作者基本信息】 首都师范大学 ， 生态学， 2008， 硕士

【摘要】 银鱼是东亚特有的一年生淡水鱼类,在长江中下游及其附属湖泊具有丰富的多样性。其中太湖新银鱼(Neosalanx taihuensis)和寡齿新银鱼(N.oligodontis)为两种常见淡水经济银鱼。本文选择长江流域天然银鱼分布区内的9个太湖新银鱼地理种群和5个寡齿新银鱼地理种群,利用分子标记技术,对线粒体DNA Cytb等基因碱基序列进行了测定,揭示了两种银鱼种群内及种群间的遗传多样性、物种地理格局并推测了物种的进化分化关系。结果显示两物种均存在丰富的种内和种间遗传分化。太湖新银鱼具有15种单倍型,其中单倍型Ⅰ、Ⅱ、Ⅲ的样本比例分别为37.0%、26.5%和26.5%,其余单倍型比例不高于2.4%。各单倍型分布范围与其相对丰度呈正比例关系:Ⅰ型分布最广,全流域都有分布,Ⅱ型集中分布于泊湖以下区域,Ⅲ型在泊湖以上水域比例较高;而其它单倍型则主要表现为局域分布。TCS网图显示,Ⅰ型应为基型,而Ⅱ、Ⅲ型平行衍生自Ⅰ型,其它单倍型分别由此三型分化而来。聚类分析结果表明,所有单倍型以Ⅰ、Ⅱ、Ⅲ型为核心聚为A、B、C三类。太湖新银鱼种群遗传多样性表现出上游低而下游高的趋势,其多样性最高的种群是位于长江中下游交界地带(古彭蠡泽区域)。寡齿新银鱼的单倍型组成特点与太湖新银鱼相似,Ⅰ、Ⅱ、Ⅲ三型分别占总样本数的39.2%、23.5%和25.5%,其它10个劣势单倍型仅占总样本数的11.8%。空间分布上,Ⅰ、Ⅱ型为广布型、Ⅲ型主要集中在梁子湖和洞庭湖区域。TCS网图显示单倍型Ⅲ为基型,Ⅰ和Ⅱ型为逐次分化出的单倍型,其它劣势单倍型分别由此三个优势单倍型分化而来。聚类分析结果表明寡齿新银鱼13个单倍型同样聚为以三个优势单倍型为核心的A、B、C三类。种群单倍型数明显呈现出下游丰富,上游匮乏的格局(洞庭湖除外),遗传多样性最丰富地区仍为中下游交界地带。两种银鱼遗传多样性空间分布格局的一致性规律表明,长江中下游交界地带应为流域淡水银鱼发生地或起源地,推测现淡水银鱼地理分布格局应是伴随着古彭蠡泽解体而分散扩布形成的。本文同时对S7核糖体基因第1内含子和AFLP两种分子标记进行了初步分析,结果显示二者均可应用于银鱼的种内遗传多样性和系统发育关系的研究。太湖新银鱼和寡齿新银鱼遗传多样性格局显示长江流域天然银鱼多样性和种质资源保护应当首先关注华阳河—鄱阳湖、梁子湖的长江中下游交界区域,以及洞庭湖湖群。在资源条件有限的情况下,应优先保护鄱阳湖和洞庭湖区域。更多还原

【Abstract】 Icefishes（Salangidae） are a group of annual economic fishes endemic to Eastern Asia.The Yangtze River basin of China shows the highest species richness of natural icefishes.The species of Neosalanx taihuensis and Neosalanx oligodontis are two popular icefishes occurred in the Mid-lower reaches of this river basin.This present study mainly focused on the genetic diversity and spatial distribution patterns of these two fish species,based on the base sequence analysis on mtDNA Cytb gene and other two genetic marks.Totally 9 populations of N.taihuensis and five populations of N.oligodontis were examined in our study.Results indicated that these two Neosalanx fishes are both enriched in intra- and inter-population genetic differentiations.Totally 15 haplotypes were checked out of 162 specimen of N.taihuensis by base sequence diversity of mtDNA Cytb gene.The three richest haplotypes ofⅠ,Ⅱ,Ⅲare predominant with percentage occurrences of 37.0%,26.5%and 26.5%,and the other haplotypes are all in much lower ratios（no more than 2.4%each）.The distribution ranges of the haplotypes indicate a positive relationship between the spatial ranges and relative abundances of haplotypes.The most predominant haplotype of typeⅠoccurred most widely along the whole river basin,haplotypeⅡoccurred in the lower reaches and typeⅢmainly in mid reaches,whereas the other rare haplotypes restricted highly in fewer local populations.The 15 haplotypes are clustered into three groups of A,B and C with a core haplotype ofⅠ,ⅡandⅢrespectively.This relationship is further supported by the network relationships deduced from TCS analysis,in which the haplotypes ofⅡandⅢgrow out of the base haplotypeⅠ,and the other 12 haplotypes evolved as the branches of typesⅠ,ⅡandⅢ.Similarly,the species of N.oligodontis has 13 haplotypes with three predominant types ofⅠ,ⅡandⅢ,which occurred in 39.2%,23.5%and 25.5%,respectively,out of 102 specimen.The types ofⅠandⅡare both diffusively inhabitated in the Yangtze River basin,but the typeⅢlimited in Lake Liangzi and Dongting in mid reaches.From TCS network,we can see that typesⅠandⅡgrow out of the base haplotypeⅢ,and the other 10 rare haplotypes further evolved from these three basic types.By cluster analysis,we get a similar relationship to TCS result.All 13 haplotypes cluster into three groups of A,B and C,with a core haplotype ofⅠ,ⅡandⅢrespectively.As result,genetic diversity of N.oligodontis populations is relatively lower in upper reaches and higher in lower reaches,and the highest population genetic diversity occurred at the joint region of the mid and lower reaches,where Lake Poyang,Liangzi and Pohu existed.The consistency of the spatial distribution patterns of these two Neosalanx populations reveals that the joint region between the mid-lower reaches must be the origin area of the freshwater icefishes in the Yangtze River basin,which further implys that current geographical distribution patterns of freshwater ice fishes in this river basin must be evolved from this region accompanied with the disaggregation of ancient Peli Lake in near history.Other two genetic marks of 1^st intron of S7 ribosome gene and AFLP（Amplified Fragment Length Polymorphism） are also used in our study.Preliminary results support our research purpose.Our results suggest that the conservation efforts on icefish diversity or genetic resource must be first focused on the key area of River Huayang,Lake Poyang and Liangzi,where the highest genetic diversity occurred.The lake area of Dongting with unique predominant haplotype must be taken as the so-called Evolutionarily Important Unit and must be also paid special attention to when we design conservation programme.更多还原