The complete mitochondrial genome of Melanostoma orientale (Diptera: Syrphidae).

The mitochondrial genome of Melanostoma orientale has been decoded by Illumina sequencing. The mitogenomic size is 16,229 bp with 40.96% A, 40.29% T, 10.60% C, and 8.15% G. It is encoded with 13 protein-coding genes, 2 ribosomal RNA, and 22 transfer RNAs. The phylogenetic tree showed that 10 species of Syrphidae, belonging to six genera, were clustered into two clades. This is the first mitochondrial genome for the genus Melanostoma.

Syrphidae is a large family of Diptera with more than 6200 species (Mengual et al. 2015; Young et al. 2016). They are known as hoverflies as their adults can pollinate for plants. Due to the lack of comprehensive identification keys, it is difficult to discriminate hoverflies by morphological characteristics (Jordaens et al. 2015; Adachi-Hagimori et al. 2018). Mitogenomic information could overcome the difficulty.

Specimens of Melanostoma orientale were collected from the campus of Guizhou Normal University (26°22′50.30″N, 106°38′11.72″E) on April 2019. The specimens (GZNU-cqq-10) were stored at the Museum of Guizhou Normal University. The mitogenome was sequenced using Illumina HiseqXten, and assembled with SOAPdenovo2 (Luo et al. 2012). Gaps were filled by Sanger sequencing. Protein-coding genes (PCGs) were identified by blasting with mitogenomes of Syrphidae. tRNAs were identified with MITOS2 (Bernt et al. 2013), and rRNAs and A + T-rich region were determined by the boundary of tRNAs. Phylogenetic tree was constructed with the whole mitogenome sequence of Syrphidae using PhyloSuite (Zhang et al. 2019).

The mitogenomic size of M. orientale (MN788095) is 16,229 bp. Melanostoma orientale shared similar gene distribution pattern with other Syrphidae species (Li et al. 2017; Pu et al. 2017; Li and Li 2019). A total of 168 bp intergenic spacers were distributed in 20 locations. The shortest intergenic spacer was 1 bp and the longest intergenic spacer was 31 bp, which was located between trnS2 and nad1. The shortest overlap, located between trnF and nad5, was 1 bp; the longest overlap, located between atp8 and atp6, nad4 and nad4l, was 7 bp. The A + T-rich region, located between rrnS and trnI, was 1270 bp. Six PCGs (cox2, atp6, cox3, nad4, nad4l and cob), four PCGs (nad2, nad3, nad5 and nad6), two PCGs (cox1 and nad1) and atp8 used ATG, ATT, ATA and ATC as start codon, respectively. Ten PCGs used TAA as stop codon. However, nad2, cox1 and nad3 used T as an incomplete stop codon.

At present, only 10 mitogenomic sequences of Syrphidae are available in NCBI. Phylogenetic tree showed that 10 species belonged to six genera (Figure 1). Eristalinus and Eristalis were clustered into one clade. The relationship of another clade was: Melanostoma + (Eupeodes + (Simosyrphus + Episyrphus)).

Figure 1.

Bayesian phylogenetic tree of 10 Syrphidae species. Bactrocera dorsalis (Diptera: Tephritidae) was selected as representative of the outgroup.