Channa gachus is a tropical and subtropical species of freshwater carnivorous fish, and they have highly or-namental and economic values in original origins.C. gachus usually live in slow-flow rivers, ditches and ponds.As for in China, they mainly inhabit in the Irrawaddy River, the Nujiang River and the Lancang River in Yunnan Province, as well as in some rivers in Hainan Province. Due to the extensive hydraulic construction, river pollution and overfishing, the number of the fish has sharply decreased. To develop effective strategies of protecting its germplasm, it is important to investigate the genetic variance and the structure of the population of this species. Previous studies have focused on the chromosome and the isoenzyme of C. gachus, as well as the phylogenetic relationship betweenC. gachusand other species in the same genus.However, the genetic backgound of this fish remains obsecure. In the present study, we sequenced 411 bp segments of mitochondrial DNA control regions of 74C. gachusindi-viduals collected from 9 populations in the Lancang River in Yunnan Province, and the Nandu River, the Wanquan River and the Changhua River in Hainan Province of China. We observed 52 mutations of nucleotide acids and 20 haplotypes. There were 3 haplotypes shared by 5 populations in Hainan Province, whereas all other haplotypes were unique in each population. We observed 3 distinct lineages in the Kimura2-parameter-based Neighbour-Joining tree. One of them was from Yunnan, and the other 2 were from Hainan—one was the Maoyang population from the Changhua River, another was from the Nandu River and the Wanquan River, and the rest two populations were from the Changhua River. The pairwise fixation indexFstwas 0.786—0.672, the gene flow was 0.153—0.244, and the inter-clade variation accounted for 74.352% of the total variation. These data indicated a significant genetic differentiation between the 3 clades. The differentiation time of the 3 clades was 2.070—0.350 Ma. The differentiation of the Hainan and Yunnan groups might have been affected by the uplift of Yunnan-Guizhou Plateau and the separation of Hainan Island from Mainland China. Following the isolation from the Maoyang population, the 2 distinct lineages in Hainan Island might be formed under the impact of the uplift of Wuzhi Mountains. Parameters such as theFst (0.765,P<0.01), the gene flow (0.149) and the genetic variation (70.360%) between the Yunnan and Hainan groups indicated a high degree of differentiation. In con-trast to the high overall genetic diversity (Hd=0.903±0.016,π=0.036±0.003), the nucleotide diversity within individual populations was much lower. The nucleotide diversity of the Qiongzhong and Shibi populations was the highest (0.008), and the Mengla population had the lowest diversity (0.000). The high overall genetic diversity might result from a mix-ture of multiple lineages. In the parsimony network ofC. gachus, the haplotypes from Yunnan Province were on one side, and the haplotypes from the Maoyan population were in the middle, and the remaining from Hainan Island were on the other side. The distribution of the haplotypes showed an atypical star-shape in the parsimony network diagram. The neutrality tests gave a non-significant negative value. Moreover, the mismatch distribution analysis displayed a multimodal distribution. These results suggested that there was no significant expansion in the population in recent history. Because there are 3 lineages of ChineseC. gachus, we recommended that they should be treated as 3 separate protected units.%为了解中国宽额鳢的遗传背景以更好地保护和开发利用资源,测定了云南澜沧江和海南岛南渡江、万泉河与昌化江等4个水系9个群体74尾宽额鳢线粒体控制区411 bp序列,发现52个变异位点和20个单倍型；在系统树上可分为云南、海南毛阳群体和海南其他群体等3个分支。谱系间Fst为0.786—0.672(P<0.01),基因流Nm为0.153—0.244；74.352%的变异来自谱系间,谱系间分化时间为2.070—0.350 Ma。推测海南与云南宽额鳢分化可能受云贵高原隆起和海南岛与陆地分离等地质事件影响；海南2个谱系的形成则可能是受到了五指山山脉隆起的影响。云南组群与海南组群间Fst为0.765(P<0.01),基因流Nm为0.149,70.360%的变异来自不同地理组群间,表明云南组群和海南组群间高度分化。相比同区域分布的鱼类,宽额鳢总体的单倍型多样性和核苷酸多样性均较高(Hd=0.903±0.016,π=0.036±0.003),其中海南琼中和石壁群体的核苷酸多样性(π)最高均为0.008；云南勐腊群体最低为0.000；但各个地理群体均比总体的遗传多样性低,可能是后者由多个谱系叠加所致。在简约性网络图中单倍型呈非典型星状分布,中性检验为非显著负值和核苷酸不配对分析呈现多峰分布,表明宽额鳢群体历史上较为稳定,没有出现显著种群扩张。
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