Characterization of the Complete Mitochondrial Genome of Liobagrus aequilabris: Phylogenetic and Taxonomic Insights into Liobagrus

Liobagrus (Siluriformes: Amblycipitidae) is a taxonomically challenging genus of torrent catfishes. Its morphological diagnoses are unstable and species boundaries contentious. Here, the complete mitochondrial genomes of two L. aequilabris individuals were sequenced, characterized, and compared with congeneric mitogenomes. The mitogenomes are double-stranded, circular molecules exhibiting the typical vertebrate organization (13 PCGs, 2 rRNAs, 22 tRNAs, and a control region), an AT-rich composition, and evidence of strong purifying selection (Ka/Ks < 1) across all PCGs, with codon-level analysis detecting episodic positive selection at only a few sites, mainly in ND4 and ND5. Maximum likelihood and Bayesian inference trees recovered Liobagrus as monophyletic, comprising two strongly supported clades: Clade I (Korea and Japan) and Clade II (Korea and northern China, subclade A; Yangtze and southeastern coastal species, subclade B). Within subclade B, the terminal assemblage of L. aequilabris and its close relatives remains poorly resolved; the two trees are topologically equivalent and differ only in displayed orientation, representing no genuine conflict. Among the nominal species examined here, conspecificity and misidentification warrant priority testing, although recent divergence (including rapid radiation with incomplete lineage sorting) and mitochondrial introgression cannot be excluded with mitochondrial data alone, underscoring the need for integrative taxonomy based on nuclear/genome-wide markers and voucher-based identification. The mitogenomes provide a molecular reference of L. aequilabris for future population, eDNA, and conservation studies.