洱海鲤属鱼类同域分化形成的分子遗传学证据

The Genetic Evidence for Sympatric Speciation Pattern of Cyprinus from Erhai Lake

对洱海的 3种鲤鱼———洱海鲤 (C .barbatus)、春鲤 (C .longipectoralis)和杞麓鲤 (C .carpiochila)线粒体DNA(mtDNA)进行了限制性片段长度多态 (RFLP)分析和mtDNA控制区 (D loop)序列测定。RFLP分析结果表明 ,16种酶在洱海鲤、春鲤和杞麓鲤 3个种共 14个个体上 ,仅DraⅠ在春鲤的一个个体上检出一个位点的限制性片段长度多态 ,独立为单倍型Ⅱ ,3个种的其余 13个个体共享单倍型Ⅰ ,种间遗传距离为 0 %～ 0 0 0 75 % ,此种间差异值比已报道的鱼类的种间差异甚至种内差异都低得多。D loop区的序列测定结果表明 ,长为 4 4 9bp的序列共显示有 7个变异位点 ,均为碱基替换 ,变异比例为 1 5 6 % ,在 14个鲤鱼个体中共检出 6种单倍型 ,种间的遗传距离为 0 0 82 %～ 0 171% ,与已研究的其他几种异域分布的鲤鱼相比 ,也至少小一个数量级。mtDNA的RFLP及D loop区的序列比较都揭示出洱海 3种鲤鱼之间的遗传差异远小于异域分布的鲤属鱼类物种之间及其他鱼类的同属种间的遗传差异。对洱海鲤属鱼类种间如此小的遗传差异唯一合理的解释就是 :它们确是由同域分化而形成的。

In the present paper,mtDNA RFLP and mtDNA D-loop sequencing were investigated in three species of Cyprinus from Erhai Lake.The results indicated that two mtDNA haplotypes were identified in three species of Cyprinus from Erhai Lake by using 16 restriction endonucleases.All individuals share the dominant type Ⅰ except one individual of C.longipectoralis shows type Ⅱ just with only one cleavage site polymorphism when tested by Dra Ⅰ.Compared to the reported interspecific and intraspecific sequence divergence in fishes,the present divergence values of 0% ～ 0.0075% from the Cyprinus species native to Erhai Lake were too much lower.Furthermore,449 bp of mtDNA D-loop region sequencing was investigated in these three Cyprinus species.There were six mtDNA haplotypes indicated by seven variation sites.The interspecific sequence divergence were 0.082% ～ 0.171%.It is also at least one degree lower than some allopatric Cyprinus species we studied.A remarkably low level of genetic divergence detected among the three species of Cyprinus species in Erhai Lake both by mtDNA RFLP and D-loop region sequencing provides direct genetic evidence for its sympatric speciation pattern,which could occurred without progressive adaptive genetic variation.