The mitochondrial genome of a rare Chinese stag beetle Kirchnerius guangxii (Coleoptera: Lucanidae)

Abstract

We sequenced the mitochondrial genome of a rare Chinese stag beetle Kirchnerius guangxii using the next-generation sequencing. The mitochondrial genome is 14,562 bp in length, containing 13 protein-coding genes (PCGs), 2 ribosomal RNA genes (rRNAs) and 22 transfer RNA genes (tRNAs). The phylogenetic analyses showed that K. guangxii was sister to the clade of Epidorcus gracilis and Serrognathus platymelus, and had a relatively low genomic affinity to Prosopocoilus. Thus, K. guangxii had a more close relationship with Epidorcus, Serrognathus and Dorcus than Prosopocoilus, which was different from previous morphological study. Our result can provide more available mitogenomic data for discussing the phylogeny of Kirchnerius and facilitate the phylogenomic research of the family Lucanidae.

Keywords:

• Mitochondrial genome
• Kirchnerius guangxii
• phylogenetic analysis

Stag beetles (The family Lucanidae Latreille) are one of the most popular insects due to their large size and decorative mandibles in males that resemble the antlers of stags, which has long received focus from taxonomists and collectors in terms of their fascinating appearance and interesting male–male fighting behavior (Tournant et al. 2012; Kim and Farrell 2015). So far, about 1800 species and subspecies within more than 100 genera are known worldwide (Krajcik 2001; Fujita 2010). The genus Kirchnerius was originally described by Schenk (2009), inferring from the type species Kirchnerius guangxii due to its unique mandible trait in large male. So far, this species is rarely noticed in the field distributed around the region of Mt. Damingshan in Guangxi. However, there were some different opinions about the systematic position of Kirchnerius because the diagnosed characters of K. guangxii at generic level partly overlapped with those in Prosopocoilus (Huang and Chen 2011, 2013; Schenk 2012). The genetic data, as different datasets, could provide new point of view to deeply understand the systematics and future conservation of this stag beetle (Lin et al. 2017; Chen et al. 2018).

In this study, we sequenced a male specimen of K. guangxii collected from Daming Mountain, Guangxi, China (108°2′E, 23°2′N), in July 2011. The sample was stored in 99% ethanol at ‒20 °C. Total genomic DNA was extracted using Blood and Tissue Kit (Qiagen, Germany) and then sequenced using Illumina HiSeq 2500 platform (GenBank accession number. MK134567). The voucher specimen (D10) was stored in the Museum of Anhui University, Hefei, Anhui, China. High-quality reads were de novo assembled using IDBA-UD (Peng et al. 2012).

Preliminary annotations were done under MITOS Web Server (Bernt et al. 2013). The mitochondrial sequence of K. guangxii is 14,562 bp in length, containing 13 protein-coding genes (PCGs), 2 ribosomal RNA genes (rRNAs), 22 transfer RNA genes (tRNAs), and partial control region. All 13 PCGs composition of the K. guangxiiis 38.28% T, 16.71% C, 31.45% A, and 13.56% G, with a strong bias toward A + T (69.73%). Similar situation occurs in the tRNAs and rRNAs, their A + T content were more than 70%. Among 13 PCGs, 12 used ATN (N represents A, C, G, T) as initiation codons, whereas the initiation codon of COX1 was AAC. Nine PCGs terminated with the stop codon TAA or TAG, whereas COX2, NAD5 and NAD4 ended with T; COX3 with TA.

Phylogentic analysis was carried out using Bayesian inference (BI) method (Ronquist et al. 2012). The ingroup includes 16 lucanid species with the available mitogenomic data from the Genbank. Three scarab beetles (Cheirotonus jansoni, Protaetia brevitarsis and Rhopaea magnicornis) were used as outgroups. The topology showed that K. guangxii was a separated branch that was sister to the two species of Epidorcus gracilis and Serrognathus platymelus, and had a relatively low genomic affinity to those species of Prosopocoilus (Figure 1). The phylogenetic analysis supported the original placement of Kirchnerius, and determined the relationship with part of stag beetle species, which also suggested that mitogenomic data could provide useful signal for the phylogenetic study as they found in other beetle groups (Breeschoten et al. 2016; Timmermans et al. 2016; Nie et al. 2018, 2020). Furthermore, a large available mitogenomic data could be good molecular marker for resolving the phylogenetic argument about the placements of other species in Kirchnerius and the phylogenetic framework of the family Lucanidae.

Figure 1. The Bayesian inference tree of 16 stag beetle species with three scarab beetles as outgroups based on 13 PCGs. Genbank accession numbers were attached to the right of the species name.

Acknowledgements

We would like to thank Mr. Cheng Hui Zhan (Shan Tou City, Guangdong, China) for his generous donation of the studied specimens of K. guangxii. We also thank Dr. Rui-e Nie (Institute of Zoology, Chinese Academy of Science, Beijing, China), Dr. Fan Song, Dr. Yun Fei Wu (Department of Entomology, China Agricultural University, West Campus, Beijing, China) and the lab member, Dan Chen, Ying Ying, Jiao Jiao Yuan for their assistance in this study.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the National Natural Science Foundation of China [No. 31872276, 31572311, 31201745].