The Mitochondrial Genomes of 18 New Pleurosticti (Coleoptera: Scarabaeidae) Exhibit a Novel trnQ-NCR-trnI-trnM Gene Rearrangement and Clarify Phylogenetic Relationships of Subfamilies within Scarabaeidae

Simple Summary: The family Scarabaeidae is one of the largest families in the insect order Coleoptera and is comprised of two quasi-systematics groups, Pleurosticti and Laparosticti. Pleurosticti is an economically important scarab group comprising about 20,000 species, the majority of which are phytophagous. Despite the innumerable studies based on ecological, molecular, and morphological characteristics, their taxonomy is still unclear and subject to many scientific hypotheses. The mitochondrial (mt) genome can provide tangible information to resolve the phylogenetic relationships within the family Scarabaeidae. However, the available mt genomes of Scarabaeidae in GenBank are underrepresented. Thus, we sequenced and analyzed 18 new phytophagous Scarabaeidae mitochondrial genomes from two subfamilies, Cetoniinae and Dynastinae, to conduct phylogenetic analyses within Scarabaeidae. This study contributes to increasing our knowledge about phytophagous Scarabaeidae.The availability of next-generation sequencing (NGS) in recent years has facilitated a revolution in the availability of mitochondrial (mt) genome sequences. The mt genome is a powerful tool for comparative studies and resolving the phylogenetic relationships among insect lineages. The mt genomes of phytophagous scarabs of the subfamilies Cetoniinae and Dynastinae were under-represented in GenBank. Previous research found that the subfamily Rutelinae was recovered as a paraphyletic group because the few representatives of the subfamily Dynastinae clustered into Rutelinae, but the subfamily position of Dynastinae was still unclear. In the present study, we sequenced 18 mt genomes from Dynastinae and Cetoniinae using next-generation sequencing (NGS) to re-assess the phylogenetic relationships within Scarabaeidae. All sequenced mt genomes contained 37 sets of genes (13 protein-coding genes, 22 tRNAs, and two ribosomal RNAs), with one long control region, but the gene order was not the same between Cetoniinae and Dynastinae species. All mt genomes of Dynastinae species showed the same gene rearrangement of trnQ-NCR-trnI-trnM, whereas all mt genomes of Cetoniinae species showed the ancestral insect gene order of trnI-trnQ-trnM. Phylogenetic analyses (IQ-tree and MrBayes) were conducted using 13 protein-coding genes based on nucleotide and amino acid datasets. In the ML and BI trees, we recovered the monophyly of Rutelinae, Cetoniinae, Dynastinae, and Sericinae, and the non-monophyly of Melolonthinae. Cetoniinae was shown to be a sister clade to (Dynastinae + Rutelinae).