中国近海细鳞鯻线粒体控制区的遗传多样性

Genetic analysis of Terapon jarbua in coastal waters of China by using mitochondrial DNA control region sequencing

通过线粒体控制区序列的分析,研究采自中国南海及东海5个群体102尾细鳞鯻的遗传多样性。发现在962 bp序列中有205个变异位点,其中135个为简约信息位点,共定义102个单倍型。中国近海细鳞鯻总体呈现出较高的遗传多样性特征(Hd=1.000,Pi=0.022),其中博鳌最高(Hd=1.000,Pi=0.028),平潭最低(Hd=1.000,Pi=0.014)。不同地理群体间无明显分化,基因交流频繁(Fst=-0.014—0.041,P>0.05);中性检验均为显著负值,推测在16.9万年—5.06万年前,即中-晚更新世出现种群扩张。系统邻接树和单倍型网络图均出现3个显著分化的谱系(谱系间Fst=0.508—0.698,P<0.001;净遗传距离Da=0.024—0.031),且各谱系中均有不同地理来源的群体。3个谱系间分歧时间大约在1.07百万年—0.24百万年前,推测可能是更新世冰期边缘海的出现导致群体隔离而产生分化。谱系A(Lineage A)包含85.3%的个体,其总体遗传多样性较高(Hd=1.000,Pi=0.012),其中平潭最高(Hd=1.000,Pi=0.014),合浦最低(Hd=1.000,Pi=0.010);群体间Fst在-0.021—0.068之间,P>0.005;AMOVA分析显示只有1.97%的变异来自于种群间,表明群体间也无明显分化;中性检验均为显著负值,推测在25.4万年—7.6万年前出现种群扩张。中国近海细鳞鯻主要受到中-晚更新世海侵和海退的影响而出现种群扩张使得谱系间发生二次接触,最终形成具有显著谱系结构但无地理分化的情况。

Terapon jarbua is a commercially important coastal water fish widely distributed across the Indo-West pacific region. To assess the genetic diversity and population structure of this species in the coastal waters of China, sequence variation in 962 base pairs of the mitochondrial DNA control region （CR） of 102 individuals from five populations were analyzed. In total, 205 polymorphic sites defined 102 haplotypes. High levels of genetic diversity （total nucleotide diversity Pi was 0.022 ±0.002, ranged from 0.014 in Pingtan to 0.028 in Boao） and no significant genetic differentiation （Fst=-0.014-0.041, P 〉 0.005） were observed. The significantly negative value of Fu＇s Fs （-23.961, P 〈 0.001） suggested a T. jarbua population expansion of approximately 0.169-0.051 Ma BP in the coastal waters of China. The neighbor-joining tree and haplotype network revealed the existence of three monophyletic matrilineal lineages, with an inter-lineage genetic distance （range：0.024-0.031） considerably greater than that within lineages. Moreover, a remarkable genetic differentiation was observed among lineages （Fst=0.508-0.698, P 〈 0.001）, the deduced divergence time among the three lineages was 1.07-0.24 Ma BP, which might have been caused by the historical isolation of sea basins in the glacial period of Pleistocene epoch. However, no such geographic structure was found, as the three lineages were composed of individuals from different localities. Lineage A comprised 85.3% of samples and showed a high level of genetic diversity （total nucleotide diversity was 0.012 ±0.001, ranged from 0.010 ±0.001 in Hepu to 0.014 ±0.001 in Pingtan）. Pairwise Fst ranged from -0.022-0.068 （P 〉 0.005）, and analysis of molecular variance showed only 1.97% variation among populations, indicated that genetic differentiation in Lineage A was not significant. Values of neutrality tests （Tajimas＇D and Fu＇s Fs） of Lineage A were significantly negative （P 〈 0.001）, and deduced population expansion time was approximately 0.254-0.076 Ma BP. The fluctuating sea levels and temperature during the period of mid-late Pleistocene might have caused divergence among these three lineages, and the secondary contact would have likely contributed to genetic homogeneity among different localities, resulted in a significant lineage structure but no geographical differentiation.