Multivariate and Geometric Morphometrics Reveal Morphological Variation Among Sinibotia Fish

Sinibotia species, investigated for morphology and species divergence owing to comparable body patterns and frequent sympatric occurrences, show high morphological similarity and close phylogenetic relationships, which challenge their accurate distinguishing via conventional morphological methods. Hence, multivariate morphometric (MM) and geometric morphometric (GM) analyses were used to assess the morphological differences between Sinibotia species (S. superciliaris, S. reevesae, S. robusta, S. pulchra, and S. zebra) habiting the Tuo River (Zizhong County) and Li and Lipu Rivers (Pingle County) based on 40 morphological traits and 34 landmarks. The morphological traits of S. robusta contrasted with those of S. pulchra and S. zebra, whereas S. superciliaris and S. reevesae showed similar morphologies, consistent with the cluster results. MM analysis using discriminant function analysis along with GM methods such as canonical variate analysis and relative distortion analysis enabled the differentiation between the Sinibotia species. Morphological variations were primarily reflected in snout length, nasal snout distance, head depth, body depth, caudal fin length, and dorsal fin length. MM effectively quantified linear size differences, whereas GM better captured and visualized complex variations in overall shape. The combined morphological evidence presented in this study contributes significantly to the identification of species, phylogenetic relationships, and ecological adaptations of Sinibotia species, thereby strengthening the theoretical rationale for the conservation and sustainable utilization of this genus.