Phylogenetic analysis of 27 species of Neritidae based on mitochondrial genomes

The family Neritidae is one of the most diverse groups within the subclass Neritimorpha, attracting widespread attention for its phylogenetic relationships. This study aims to explore the evolutionary relationships, genetic distances, and selection pressures of 27 species of Neritidae through a phylogenetic analysis of their mitochondrial genomes, and to finally provide a theoretical basis for the systematic evolution and origin of Neritidae. Utilizing bioinformatics methods, the study analyzed the sequence base composition, selection pressure on protein-coding genes, and genetic distances of 27 Neritidae species. Using three different tree reconstruction methods (Astral, Bayesian inference, and maximum likelihood) for protein-coding genes, the study reconstructed the phylogenetic tree. Results revealed that the mitochondrial genomes of 27 Neritidae species were all double-stranded closed circular DNA molecules, containing 37 genes (13 protein-coding genes, 2 ribosomal rRNA genes, 22 transfer RNA genes, and a non-coding control region). There was no gene rearrangement among species. The full length of the mitochondrial genomes involved in this study ranged from 15 261 to 15 975 bp, displaying a noticeable AT bias in base composition. The results of relative synonymous codon usage (RSCU) indicated that the usage frequencies of UUA, CCU, CGA and UCU were high, while that of CCG was the lowest. Ka/Ks analysis indicated purifying selection on mitochondrial protein-coding genes in the evolutionary process. Among the 13 protein-coding genes, ATP8 exhibited the fastest evolutionary rate, while COX2 showed the slowest. All three tree construction methods yielded consistent results, revealing the average genetic distances of each protein-coding gene ranged from 0.16 to 0.29. Among them, the gene with the largest average genetic distance was ND6 and the one with the smallest average genetic distance was COX1. The 27 Neritidae species were grouped into three evolutionary branches. The first branch consisted of 15 species of genus Nerita, with a distinct evolutionary relationship compared to other genera. The second branch comprised 6 species of genus Clithon and one species of genus Vitta. Species of genus Neritina, Neripteron and Septaria formed the third branch. This study indicates that the mitochondrial genomes of the 27 Neritidae species exhibit high conservation in structure and gene arrangement but differ in evolutionary relationships due to variations in living environments and lifestyles. This research provides a detailed molecular biology foundation for understanding the systematic evolution of Neritidae.