从线粒体控制区全序列变异看短颌鲚和湖鲚的物种有效性

Species validities of Coilia brachygnathus and C.nasus taihuensis based on sequence variations of complete mtDNA control region

经克隆测序获得我国七丝鲚(Coiliagrayii)、凤鲚(C.mystus)、刀鲚(C.nasus)和短颌鲚(C.brachygnathus)以及太湖湖鲚(C.nasus taihuensis)等4个种和1亚种32尾个体的mtDNAD-loop区全序列,以日本鳀(Engraulis japonicus)和秘鲁鳀(E.ringens)为外类群构建了中国鲚属的分子系统发育树,并讨论了短颌鲚和湖鲚的物种有效性。结果显示,七丝鲚的D-loop区全序列长1,208bp,凤鲚1,279-1,361bp,刀鲚1,252-1,290bp,短颌鲚1,214-1,252bp,湖鲚1,252-1,442bp,除七丝鲚外的其他种类个体间均表现出序列长度的多态性。短颌鲚、刀鲚和湖鲚三者间的平均K2-P遗传距离仅为0.011-0.020,明显小于它们与凤鲚、七丝鲚及外类群间的遗传距离(0.051-0.349)。以邻接法和最大简约法构建的系统发育树表明,刀鲚、短颌鲚及湖鲚均未各自构成单系,而是共同构成一个单系群,三者并未发生显著分化。研究表明,短颌鲚和湖鲚为刀鲚的淡水生态型种群,并非有效物种。系统发育分析表明,中国鲚属3个有效物种间以凤鲚最为原始,刀鲚和七丝鲚为姐妹群,处于较进化的位置。推测凤鲚可能是鲚属祖先种最早从起源中心扩散到西北太平洋的后裔,而刀鲚和七丝鲚则是凤鲚在演化过程中分别适应寒冷和温暖气候而分化出的物种。

We determined 32 complete mitochondrial control region （D-loop region） sequences of Coilia species, including C. nasus, C. grayii, C. mystus, C. brachygnathus and the so-called C. nasus taihuensis, to investigate the validity of disputed species C. brachygnathus and C. nasus taihuensis, and to discuss the phylogenetic relationships of Coilia in China. Engraulis japonicus and E. ringens were used as outgroups. Sequences length ofC. grayii, C. mystus, C. nasus, C. brachygnathus and C. nasus taihuensis were 1,208 bp, 1,279-1,361 bp, 1,252-1,290 bp, 1,214-1,252 bp, and 1,252-1,442 bp, respectively. Except for C. grayii, other Coilia species have length variations among individuals. The average K 2-P distances among C. brachygnathus, C. nasus and C. nasus taihuensis ranged from 0.011 to 0.020, while the average distances between these three species and the species of C. grayii, C. mystus and outgroups ranged from 0.051 to 0.349, thus showing significant difference between the former and latter species. The phylogenetic trees estimated by maximum parsimony （MP） and neighbor-joining （N J） methods indicated that the individuals of C. nasus, C. nasus taihuensis and C. brachygnathus failed to form monophyletic clades. These results revealed that C. nasus taihuensis and C. brachygnathus should be considered the same species and C. nasus is a valid species name. The phylogenetic result also suggests that C. mystus is the most basal among the three valid species of Coilia, while C. grayii and C. mystus are more derived and are sister groups. We presume that C. mystus is the earliest descendant of Coilia ancestor which dispersed from the original center to the northwest Pacific Ocean. C. nasus and C. grayii are the species diverged from C. mystus adapted to cold and warm environment, respectively.