Otolith Morphology of Bahaba taipingensis and Its Closely Related Species: Implications for Species Discrimination and Phylogenetic Signals

Otolith morphology has long been recognized as an effective tool for fish species discrimination; however, the extent to which it reflects phylogenetic relationships remains debated, particularly among closely related taxa. In this study, we investigated otolith and sulcus morphology in the critically endangered Chinese bahaba (Bahaba taipingensis) and four closely related sciaenid species to evaluate their taxonomic utility as well as phylogenetic and evolutionary significance. Otolith and sulcus outlines were quantified using wavelet coefficients, species discrimination was performed with a random forest classifier, and associations between morphological variation and genetic divergence were assessed through phylogenetic reconstruction based on the 13 mitochondrial protein-coding genes and Mantel tests. Otolith outlines exhibited significant interspecific variation and achieved a high classification accuracy of 90.32%, whereas sulcus morphology achieved 78.06%, demonstrating that both morphological traits are effective for species identification, with otolith outlines providing greater discriminatory power. Wavelet coefficient analyses further revealed that low-level coefficients, representing overall outline features, contributed most to species discrimination, whereas high-level coefficients, representing fine-scale marginal features, were more closely associated with genetic divergence. A significant correlation was detected between fine-scale otolith shape variation and mitochondrial genetic distance, indicating that otolith morphology retains a detectable phylogenetic signal among closely related sciaenid species. In contrast, sulcus morphology showed only a comparatively weak association with phylogeny, suggesting that otolith and sulcus morphology have followed partially independent evolutionary trajectories. Overall, our findings demonstrate that otolith outline and sulcus morphology provide complementary characters for species identification, and that detailed otolith morphology better reflects evolutionary history than sulcus morphology. This study establishes a practical identification framework for B. taipingensis and its closely related species and provides a morphological foundation for future investigations of archeological otoliths, historical population dynamics, and evolutionary diversification within Sciaenidae.