# Comparative Analyses Reveal Mitogenome Characteristics of Halictidae and Novel Rearrangement (Hymenoptera: Apoidea: Anthophila)

## TL;DR

This study sequenced four new bee mitogenomes, revealing gene rearrangements and phylogenetic relationships in Halictidae, a key pollinator group.

## Contribution

The discovery of a novel gene rearrangement pattern in bees and the sequencing of four new Halictidae mitogenomes.

## Key findings

- Five gene rearrangement patterns were identified, including one novel pattern in bees (ND4-trnP-ND4L-trnT).
- Phylogenetic analysis showed Rophitinae as the basal group within Halictidae.
- Mitogenomes had high AT content (82.55–86.44%) and specific codon usage preferences like UUA and UCA.

## Abstract

Species of Halictidae are renowned for their outstanding pollination function and variable social behavior, while our understanding of the evolutionary history of this group has been hindered by the scarce molecular data. In this study, we newly obtained four mitogenomes of Halictidae. Using comprehensive comparative genomic methods, we analyzed the mitogenome base composition and codon usage of Halictidae which are similar to published bee species. We found five gene rearrangement patterns, including one novel pattern of bees. Furthermore, we combined published data to reconstruct phylogenetic relationships based on Bayesian Inference and Maximum Likelihood methods. Our study enriches molecular databases for research on bees and provides resources for further study on the evolutionary biology of Halictidae.

Halictidae, as a major pollinator family in bees, has significant ecological value. However, the insufficient molecular data for this group has limited our understanding of the evolutionary history of this group. Herein, we newly sequenced and assembled four mitogenomes of Halictidae, including three species of Nomiinae and one species of Rophitinae. We analyzed the characters of the newly obtained mitogenomes, including nucleotide composition, sequence length, and gene rearrangements. The length of the newly sequenced mitogenomes ranged from 16,492 to 21,192 bp, and all newly obtained mitogenomes contained 22 tRNAs, 13 protein-coding genes, two rRNAs, and one control region. Their AT content (%) ranged from 82.55 to 86.44. Relative synonymous codon usage analysis showed that UUU, UUA, and AUU were the preferred codons. The relative synonymous codon usage > 2 of mostly newly sequenced species was as follows: UUA > UCA > CGA. All newly obtained mitogenomes show gene rearrangement; we found five gene rearrangement patterns in total. Notably, ND4-trnP-ND4L-trnT was the first reported gene rearrangement pattern in bees. In addition, we reconstructed the phylogenetic relationships of Halictidae based on 10 species (eight ingroups and two outgroups), using Bayesian Inference and Maximum Likelihood approaches. Phylogenetic analysis showed that Rophitinae was the basal group within Halictidae.