The mitochondrial genome of Syntormon pallipes (Diptera: Dolichopodidae)

Abstract

The long-legged fly Syntormon pallipes belongs to the subfamily Sympycninae of Dolichopodidae. The mitogenome of S. pallipes was sequenced as the first representative of the subfamily. The mitogenome is 15,583 bp long, consisting of 13 protein-coding genes, 2 rRNAs, and 22 transfer RNAs. Syntormon pallipes has the similar gene structures with other published species of Dolichopodidae. The nucleotide composition biases toward A, and T is 78.1% of the entirety. Bayesian inference analysis strongly supported the monophyly of Dolichopodidae, which was inferred from 14 species. It indicated that Sympycninae and Hydrophorinae were assigned to be the sister of the clade of ((Rhaphiinae + Neurigoninae) + (Dolichopodinae + Sciapodinae)).

Keywords:

• Mitochondrial genome
• Sympycninae
• Syntormon
• phylogenetics

Introduction

Sympycninae is a large subfamily of the family Dolichopodidae, and the genus Syntormon is the largest genus of the subfamily Sympycninae with 110 species known around the world (Yang et al. 2006, 2011; Grichanov 2017). The species of Syntormon are usually found in the habitats near freshwater with stones or plants.

The adult specimens of S. pallipes used for this study were collected from Lishan Mountain (35°44′814″N, 112°01′536″E, 1200 m) of Shaanxi in China in 2013. The specimens of S. pallipes were deposited in the Entomological Museum of China Agricultural University (CAU). The total genomic DNA was extracted from the whole body (except head) of the specimen using the QIAamp DNA Blood Mini Kit (Qiagen, Germany) and stored at −20 °C. The nearly complete mitogenome of S. pallipes is 15,583 bp long. It encoded 13 PCGs, 22 tRNA, 2 rRNA genes and the control region could not be sequenced entirely in this study, and was similar to related reports before (Kang et al. 2016; Li et al. 2016; Qilemoge et al. 2018; Wang, Ding, et al. 2016; Wang, Liu, et al. 2016; Wang, Wang, et al. 2016; Li et al. 2017; Zhou et al. 2017). The nucleotide composition of the mitogenome was biased toward A and T, with 78.1% of A + T content (A = 38.9%, T = 39.2%, C = 12.5%, and G = 9.4%). The total length of all 13 PCGs of S. pallipes is 11,104 bp. All PCGs in S. pallipes utilize the conventional translational start codons for invertebrate mtDNA. For example, six PCGs (ATP6, COII, COIII, CYTB, ND4, and ND4L) initiated with ATG codons, four PCGs (COI, ATP8, ND2, ND3, ND5, and ND6) initiated ATT codons, and ND1 initiated with ATA codons. Ten PCGs used the typical termination codons TAA; two PCGs (CYTB, ND3) used TAG and ND4 used T in S. pallipes.

Phylogenetic analysis was performed based on the nucleotide sequences of 13 PCGs from 14 Diptera species. Bayesian (BI) analysis (Figure 1) showed that monophyletic Empidoidea (Empididae + Dolichopodidae) was assigned to be the sister group to the clade of Xylophagidae and Asilidae. For the phylogeny of Empidoidea, monophyletic Empididae was assigned to the sister to monophyletic Dolichopodidae. For the phylogeny of Dolichopodidae, Sympycninae and Hydrophorinae were assigned to be the sister of the clade of ((Rhaphiinae + Neurigoninae) + (Dolichopodinae + Sciapodinae)). The phylogenetic relationship within Empidoidea is very clear: Empididae + (Sympycninae + Hydrophorinae) + ((Rhaphiinae + Neurigoninae) + (Dolichopodinae + Sciapodinae))). The phylogenetic position of Sympycninae was also supported by the morphological study (Yang et al. 2006, 2011). The mitogenome of S. pallipes could provide important information for the further studies of Dolichopodidae phylogeny.

Figure 1. The phylogenetic tree of Bayesian interface analysis based on 13 PCGs; the colors of leaves in phylogenetic tree represent their families showed on the left corner of picture above.

Disclosure statement

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

Additional information

Funding

This study was supported by National Key Research and Development Plan from the Ministry of Science and Technology of China [2017YFD0201000], the National Natural Science Foundation of China [31772497] and Ministry of Science and Technology of the People’s Republic of China [2005DKA21402].