Exploring the Complete Mitochondrial Genome of Schizothorax biddulphi via PacBio HiFi Sequencing: Phylogenetic Insights and Molecular Evolutionary Implications

This study presents the first complete and fully assembled mitochondrial genome (mitogenome) of Schizothorax biddulphi derived from PacBio HiFi sequencing technology, providing novel insights into its phylogenetic relationships within the Cyprinidae family. The mitogenome of S. biddulphi exhibits a canonical structure typical of teleost fishes, comprising 13 protein-coding genes (PCGs), 22 transfer RNA (tRNA) genes, 2 ribosomal RNA (rRNA) genes, and a control region (D-loop). Most PCGs initiate with the standard ATG codon, and termination is achieved through TAA, TAG, or truncated T stop codons, suggesting a potential influence of selection pressure on these regions. Comparative genomic analysis indicates high conservation of gene order and nucleotide composition with other Schizothorax species. Phylogenetic analyses using both maximum likelihood (ML) and Bayesian inference (BI) methods reveal that S. biddulphi and Schizothorax eurystomus form a well-supported clade, indicating a close phylogenetic relationship between these two species. These results contribute novel insights into the phylogenetic relationships within the genus Schizothorax and underscore the evolutionary divergence of S. biddulphi from other congeneric species. The newly characterized mitogenome enhances the available genetic resources and offers a valuable reference for future phylogenomic studies. This research provides a foundation for understanding the evolutionary dynamics driving diversification and adaptive radiation within Schizothorax . Furthermore, it underscores the significance of mitogenomics in elucidating the ecological adaptations and biological success of these freshwater fishes.