西藏湖泊长刺溞复合种的系统进化关系

本文通过对西藏湖泊长刺溞复合种(Daphnia longispina complex)中分布最广的3个物种, 即长刺溞(D. longispina)、盔形溞(D. galeata)和颈齿溞(D. dentifera)线粒体COI基因序列以及GenBank中欧洲的长刺溞、加拿大的颈齿溞和我国东部低海拔地区的盔型溞COI基因序列的比较分析, 研究了西藏湖泊长刺溞复合种的系统进化关系, 发现西藏地区的盔型溞、颈齿溞和长刺溞均已出现较大分化。颈齿溞种群内遗传差异度为0.33-2.32%, 盔型溞为0.33-2.74%, 长刺溞的遗传差异度最高, 为1.31-5.50%。基于COI基因序列构建的最大似然树和贝叶斯系统树均表明, 长刺溞复合种由3个进化分支组成, 分别对应长刺溞、盔型溞和颈齿溞, 三者之间的遗传差异度为9.40-16.98%(Kimura 2-parameter双参数模型)。基于COI基因单倍型(haplotype)所构建的网络关系也支持上述3个分支的存在。早期记录虽然显示长刺溞在我国分布较广, 但本次调查只在班公错有发现, 相比之下, 盔形溞和颈齿溞则分布更广。我们的研究表明, 由于形态学鉴定上的局限性, 早期的长刺溞记录很可能混杂了容易引起混淆的盔型溞或颈齿溞。

Phylogenetics of the Daphnia longispina complex in Tibetan lakes

To understand the phylogeography of the Daphnia longispina complex (consisting of three species: Daphnia longispina, Daphnia galeata and Daphnia dentifera) in the lakes of Tibet, we amplified the mitochondria COI sequences of the Daphnia longispina complex from Tibetan lakes and compared these with sequences from GenBank (containing Daphnia longispina from Europe, Daphnia galeata from the low altitudes area of eastern China, and Daphnia dentifera from Canada). Results showed that there is significant differentiation within Daphnia longispina, Daphnia galeata and Daphnia dentifera in the lakes of Tibet. The genetic diversity within Daphnia dentifera is 0.33-2.32%, 0.33-2.74% for Daphnia galeata, and 1.33-5.50% for Daphnia longispina, representing the largest among the three species. Both Maximum Likelihood and Bayes trees based on mitochondria COI sequences showed that the Daphnia longispina complex was composed of three obvious clades, corresponding to Daphnia longispina, Daphnia galeata and Daphnia dentifera, respectively. The genetic diversity among the clades was 9.40-16.98%, according to a Kimura 2-parameter model. Haplotype network based on the mitochondria COI sequences showed that the Daphnia longispina complex was composed of three branches, corresponding to Daphnia longispina, Daphnia galeata and Daphnia dentifera, respectively. Early Chinese records showed that Daphnia longispina was widely distributed, but in this present study, Daphnia longispina only appeared in Lake Bangongcuo, and Daphnia galeata and Daphnia dentifera were more widely distributed. Because of the difficulty in morphological identification as well as the lack of molecular data in early investigations, the early records of Daphnia longispina in China were probably confused with Daphnia galeata or Daphnia dentifera.