Phylogenetic Analysis of Some Species of the Group (Diptera: Culicidae) in China Based on Complete Mitochondrial Genomes.

Some species of the Hyrcanus group are vectors of malaria in China. However, the member species are difficult to identify accurately by morphology. The development of sequencing technologies offers the possibility of further studies based on the complete mitochondrial genome. In this study, samples of mosquitoes of the Hyrcanus group were collected in China between 1997 and 2015. The mitochondrial genomes of ten species of the Hyrcanus group were analyzed, including the structure and base composition, codon usage, secondary structure of tRNA, and base difference sites in protein coding regions. Phylogenetic analyses using maximum-likelihood and Bayesian inference were performed based on mitochondrial genes and complete mitochondrial genomes The mitochondrial genome of 10 Hyrcanus group members ranged from 15,403 bp to 15,475 bp, with an average 78.23% (A + T) content, comprising of 13 PCGs (protein coding genes), 22 tRNAs, and 2 rRNAs. Site differences between some closely related species in the PCGs were small. There were only 36 variable sites between and for a variation ratio of 0.32% in all PCGs. The pairwise interspecies distance based on 13 PCGs was low, with an average of 0.04. A phylogenetic tree constructed with the 13 PCGs was consistent with the known evolutionary relationships. Some phylogenetic trees constructed by single coding regions (such as COI or ND4) or combined coding regions (COI + ND2 + ND4 + ND5 or ND2 + ND4) were consistent with the phylogenetic tree constructed using the 13 PCGs. The phylogenetic trees constructed using some coding genes (COII, ND5, tRNAs, 12S rRNA, and 16S rRNA) differed from the phylogenetic tree constructed using PCGs. The difference in mitochondrial genome sequences between and was very small, corresponding to intraspecies difference, suggesting that the species was in the process of differentiation. The combination of all 13 PCG sequences was demonstrated to be optimal for phylogenetic analysis in closely related species.