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The species limits of Cranoglanis remain controversial despite their relevance to freshwater fish conservation in southern China. We analyzed mitochondrial cytochrome b sequences from 203 individuals representing seven geographic populations across the Pearl, Red, and Nandujiang drainages to test species validity, assess genetic structure, and infer demographic history. Phylogenetic and haplotype network analyses recovered two deeply divergent lineages: a widespread Clade A distributed across all three drainages and a geographically restricted Clade B confined to the middle Xijiang system of the Pearl River Basin. The traditionally recognized Pearl River, Hainan, and Red River nominal taxa all fell within Clade A rather than forming three independent maternal lineages. Within Clade A, differentiation between the Yuanjiang–Red River and Pearl River populations was low, whereas the Nandujiang population showed significant differentiation and extremely low nucleotide diversity. Divergence dating estimated separation between Clades A and B at 4.9183 Ma. Both lineages showed signals consistent with historical demographic expansion. Our results support recognition of two evolutionarily significant units within Cranoglanis and identify the Nandujiang population as a priority for conservation, while the taxonomic status of Clade B requires further testing with nuclear and morphological evidence.
Huang et al. (Thu,) studied this question.