Genetic variations of three populations ( Liangzi Lake population of 19, Longwo Lake population of 19 and Huaihe River population of 18) of Plagutgnathops microlepis were studied by sequence analysis of mitochondrial cytochrome b(Cyt b) gene. Gene fragments of 1149 bp were acquired by PCR and DNA sequencing techniques. There were 10 haplotypes, 116 nucleotide variable sites and 10.09% of nucleotide polymorphic loci among three populations of Plagiognathops microlepis. As a base composition , the content of A + T( about 57% ) was obviously higher than that of C + G. Highest nucleotide diversity was observed in Huaihe River population(5 haplotypes, 111 nucleotide variable sites and 0. 031223 of nucleotide diversity index), and lowest nucleotide diversity was detected in Longwo Lake population(3 haplotypes, 2 nucleotide variable sites and 0.000550 of nucleotide diversity index). Genetic distances between populations of Liangzi Lake and Longwo Lake, between populations of Huaihe River and Liangzi Lake, and between populations of Huaihe River and Longwo Lake were 0.001530, 0.084682 and 0.084335, respectively. There was a closer genetic relationship between populations of Liangzi Lake and Longwo Lake than that between populations of Huaihe River and the other two. Genetic difference between populations of L iangm Lake and Longwo Lake has not risen to subspecies level, while genetic divergence between populations Huaihe River and L.iangri Lake and between populations Huaihe River and Longwo Lake may have arrived at subspecies level.%应用线粒体Cyt b基因序列分析法,研究了细鳞斜颌鲴三个群体(粱子湖群体19尾、龙窝湖群体19尾、淮河群体18尾)的遗传变异关系.结果显示:细鳞斜颌鲴线粒体Cyt b基因大小为1149 bp.三个群体共测出10种单倍型,116个核苷酸变异位点,多态位点百分率为10.09％,碱基组成中A+T含量(57％左右)明显高于G+C含量.淮河群体含5种单倍型、111个变异位点,核苷酸多样性指数为0.031223,核苷酸多样性最丰富；龙窝湖群体含3种单倍型、2个变异位点,核苷酸多样性指数为0.000550,核苷酸多样性最简单.梁子湖-龙窝湖、淮河-粱子湖、淮河-龙窝湖群体间的遗传距离分别是0.0015300.084682和0.084335.梁子湖-龙窝湖群体间遗传关系较近,群体间的遗传分化仍在亚种范围内；而淮河-梁子湖、淮河-龙窝湖群体间亲缘关系较远,群体间的遗传分化可能已达到亚种水平的分化.
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