Complete Mitochondrial Genome Analysis of Daphniopsis tibetana (Branchiopoda: Diplostraca): New Insights into the Taxonomy of the Genus and Its Phylogenetic Implications for Branchiopoda

Daphniopsis tibetana is widely distributed in Xinjiang, Qinghai, Tibet of China, as well as in Russia and India, which is the dominant zooplankton in many high-altitude (4000 m) salt lakes. D. tibetana can adapt to saline waters, whereas the other species of the superorder Cladocera can only inhabit in freshwater. However, the phylogenetic status of D. tibetanain Branchiopoda remains unclear primarily because of limited mitogenome. In this study, complete mitochondrial genome sequences of D. tibetanawere sequenced and annotated for the first time to obtain a comprehensive understanding of its phylogenetic status. The complete mitogenome of D. tibetanais 16196 bp in length. It contains 37 genes, including two ribosomal RNAs (12S and 16S rRNAs) genes, 22 transfer RNA (tRNA) genes, 13 protein-coding genes, and one non-coding region. The overall base composition is 29.6% A, 33.2% T, 19.0% G, and 18.2% C with a high AT bias (62.8%). Except for trnS1 (GCT), most tRNAs have a typical cloverleaf secondary structure. Phylogenetic analysis based on maximum likelihood and Bayesian inference generates identical phylogenetic topology and shows the phylogenetic status of D. tibetana, which reconfirm the distinction between the genera Daphniopsis and Daphnia. Meanwhile, the class Branchiopoda is clustered into three clades (Anostraca, Notostraca, and Diplostraca) with high support values. These results provide not only a comprehensive understanding of the characteristics of D. tibetana mitogenome and its phylogenetic position in Diplostraca, but also information for future research on the phylogeny of Branchiopoda.