Mitochondrial phylogeny of two ball-rolling dung beetles, Gymnopleurus mopsus and Gymnopleurus geoffroyi (Coleoptera: Scarabaeidae: Scarabaeinae), with notes on the phylogenetic relationships within Scarabaeinae

The tribe Gymnopleurini is a well-known group within Scarabaeinae, characterized by its diurnal ball rolling behavior. While mitochondrial genomes have been reported for numerous Scarabaeinae species, those of Gymnopleurini remain unexplored. Mitogenomic phylogenetic analysis can provide a better understanding of the phylogenetic relationships within Scarabaeinae. In this study, we document the mitochondrial genome sequences of two ball-rolling dung beetles, Gymnopleurus mopsus (Pallas, 1781) and G. geoffroyi (Fuessly, 1775) and infer the phylogenetic relationship and position of Gymnopleurini. The mitochondrial genomes of the two species are circular DNA molecules, 15,591 bp and 15,460 bp in size, respectively, and consist of 37 genes, with an identical gene order in Scarabaeinae. Mitochondrial phylogeny, based on the sequences of 13 protein-coding genes (PCGs) from 72 Scarabaeinae species, recovered monophyly of Scarabaeinae and a sister relationship between Gymnopleurus (Gymnopleurini) and Sarophorus. This finding is the first to suggest a potential sister relationship between two groups, but like previous studies, the lack of strong synapomorphic characters implies further phylogenomic analysis is needed to confirm their relationship. Notably, the monophyly of the Onthophagini + Oniticellini linenage was supported, reflecting its biogeographic history and highlighting the need for a taxonomic revision of this species-rich and cosmopolitan group, incorporating additional suprageneric groups. Our mitochondrial genome information of G. mopsus and G. geoffroyi can also contribute to future conservation efforts by providing insights into the genomic diversity and population structure of these two threatened species.