# Mitochondrial Genome Comparison and Phylogenetic Analysis of Four Species of Dung Beetles (Coleoptera: Scarabaeidae: Scarabaeinae)

## TL;DR

This study analyzes the mitochondrial genomes of four dung beetle species, revealing new gene arrangements and evolutionary relationships within the Scarabaeinae subfamily.

## Contribution

The study reports novel mitochondrial gene rearrangements in dung beetles and provides phylogenetic insights into Scarabaeinae tribes.

## Key findings

- Mitochondrial genome sizes ranged from 14,977 bp to 18,425 bp across four dung beetle species.
- Unique gene rearrangements were identified in Copris magicus and Liatongus bucerus.
- Phylogenetic analysis supported monophyly for Onitini and Oniticellini tribes and multilineage origins for Coprini and Onthophagini.

## Abstract

Dung beetles, despite their well‐documented ecological significance, remain surprisingly underrepresented in molecular biology research, with a notable paucity of genomic and molecular data available for this ecologically crucial insect group. We sequenced and analyzed the whole mitochondrial genomes of four species of dung beetles, including Catharsius molossus, Liatongus bucerus, Copris magicus, and Onitis falcatus from the Scarabaeinae subfamily. The results showed that the mitochondrial genome sizes of the four dung beetle species ranged from 14,977 bp to 18,425 bp. Among them, the mitochondrial genome structure, base composition, codon usage, and gene arrangement of
L. bucerus
and C. magicus were relatively conserved, consistent with other Coleoptera species. However, C. magicus exhibited a unique rearrangement, with the trnT and trnP genes undergoing positional swapping, resulting in the formation of a trnP‐trnT tRNA gene block. In
L. bucerus
, a long‐distance translocation of the trnI gene and rearrangement between the trnS2 and nad1 genes occurred, leading to the formation of a trnS2‐trnI tRNA gene block. This represents the first identification of such rearrangements in Scarabaeidae. The phylogenetic reconstruction of mitochondrial protein‐coding genes in 63 species of Scarabaeinae revealed significant insights into their evolutionary relationships. It supported multilineage for the tribes Coprini and Onthophagini, and monophyly for the tribes Onitini and Oniticellini. Coprini maintained close affinities with Deltochilini, Dichotomiini, Phanaeini, Ateuchini, and Eurysternini, with Phanaeini as a sister group to each other, and the phylogenetic relationships among the tribes supported the existing findings. It clarified the position of four dung beetles in their respective clades and genera. This study could enrich the genetic data of Scarabaeidae and establishes a foundation for further understanding of the evolutionary relationships of dung beetles.

Dung beetles have important ecological and economical values; however, the molecular research of the taxonomic group is very limited. We sequenced mitochondrial genomes of four Scarabaeinae species, with sizes from 14,977 to 18,425 bp, and identified novel gene rearrangements. Phylogenetic analysis of 63 Scarabaeinae species supported multilineage origins for Coprini and Onthophagini tribes, monophyly for Onitini and Oniticellini, and clarified evolutionary ties between tribes, aligning with existing classifications. This work enriched Scarabaeidae genetic data and advanced understanding of dung beetle evolution, and provided a foundation for future molecular and ecological studies.