Complete Mitochondrial Genomes of Three Rhinoceros Beetles (Coleoptera: Scarabaeidae: Dynastinae) and Phylogenetic Implications

The subfamily Dynastinae, commonly known as rhinoceros beetles, represents one of the most morphologically striking lineages within the Scarabaeidae. This distinctiveness arises from the elaborate horns present on the head and pronotum of many species, particularly in males. Despite their significant ecological and economic importance, the phylogenetic relationships within this subfamily remain poorly understood, and available mitochondrial genomic data are remarkably scarce, hindering comprehensive phylogenomic analyses. In this study, we sequenced the complete mitochondrial genomes of three dynastine species for the first time, including the first representatives for the tribes Pentodontini and Cyclocephalini. All three genomes contain the typical set of 37 mitochondrial genes; however, a rearrangement in the tRNA gene cluster trnQ-trnI-trnM was observed. Given that this rearrangement is also present in other lineages within the subfamily Dynastinae but not in any other subfamilies, we propose it as a potential synapomorphy for Dynastinae. Furthermore, all three newly sequenced genomes exhibit relatively large sizes, which may be attributed to their expanded control regions. By integrating these sequences with existing Scarabaeidae mitogenome data, we reconstructed the phylogeny of Dynastinae. Our results showed that the tribes Dynastini and Oryctini were not monophyletic, suggesting the need for a taxonomic revision of these tribes. Our results also support the three-subtribe hypothesis for the tribe Dynastini.