First complete mitochondrial genome from the genus Coptodryas (Coleoptera: Curculionidae: Scolytinae) and its phylogenetic implications.

The complete mitochondrial genome (mitogenome) of Coptodryas elegans was determined, which represents the first sequenced mitogenome from Coptodryas. This mitogenome is 15,959 bp in size and comprises 36 typical coding genes and a control region, the tRNAIle was not detected in this mitogenome, as observed in other species of Curculionidae. The monophyly of the family Scolytinae and the sister relationship between C. elegans and Cyclorhipidion bodoanus is supported by maximum likelihood analysis derived from the protein-coding gene sequences.

Coptodryas Hopkins, 1915 is a small genus, belonging to Xyleborini within Scolytinae, which is mainly distributed in tropical Asia and rare in Melanesia (Smith et al. 2020). Here, we described the complete mitogenome of Coptodryas elegans (Sampson, 1923), representing the first mitogenome from the genus Coptodryas, which will contribute to the molecular identification of this important pest and phylogenetic study of the Scolytinae.

The sample was collected from Chaozhou, Guangdong, China (N 23°85′11″ and E 116°63′26″) on 7 July 2019. Voucher specimen is stored at the Department of Entomology, South China Agricultural University (voucher no. X1, Xingmin Wang, wangxmcn@scau.edu.cn). Genomic DNA extraction was performed using the DNeasy Blood and tissue kit. An Illumina TruSeq library was prepared with an average insert size of 350 bp and sequenced using the Illumina Hiseq 2500 platform with 150 bp paired-end reads. High quality reads were used to produce a de novo assembly using IDBA-UD (Peng et al. 2012). Genomic annotations were performed using MITOS2 (Bernt et al. 2013) and tRNAscan-SE 2.0 (Lowe and Chan 2016), and the result was further confirmed using NCBI-BLAST (Figure 1).

Figure 1.

Phylogeny analysis of Scolytinae based on the concatenated nucleotide sequences of protein-coding genes. The newly sequenced C. elegans mitogenome is highlighted using bold and black.

The complete mitogenome of C. elegans is 15,959 bp in size, including 13 protein-coding genes (PCGs), 21 transfer RNA genes (tRNAs), two ribosomal RNA genes (rRNAs), and a control region. The tRNA was not detected in the C. elegans mitogenome, as observed in other species of Curculionidae (Yang et al. 2018). The A + T content of the mitogenome is 73.7% (A = 40.7%, T = 33.1%, C = 16.7%, G = 9.5%) which is significantly biased toward AT. All PCGs initiate with ATN codons (four with ATA, four with ATG, three with ATT, and two with ATC). There are 21 tRNA genes, ranging from 63 to 72 bp in length. As in most other insect mitogenomes (Huang et al. 2021), the large and small rRNAs in C. elegans were located between tRNA and and between tRNA and the control region, respectively. The length of lrRNA and srRNA was determined to be 1301 bp and 783 bp, respectively.

Sequences of 13 PCGs from 18 Scolytinae species and two outgroup taxa from Curculioninae, were aligned by MAFFT 7.0 (Katoh and Standley 2013) and concatenated for phylogenetic analysis. Phylogenetic tree was inferred under the maximum-likelihood analysis using IQ-TREE 1.6.5 (Trifinopoulos et al. 2016). The monophyly of the Scolytinae is recovered with high supported (BS = 96) and the newly sequenced species C. elegans shows close relationship with Cyclorhipidion bodoanus (BS = 66).