# The Geographical Differences in the Morphology of Diptychus maculatus: Environmental Driving Factors and Adaptive Evolution

## TL;DR

This study explores how environmental factors and human impacts shape the physical traits of Diptychus maculatus fish in different regions of the Tarim River Basin.

## Contribution

The study integrates traditional and geometric morphometrics to reveal how environmental and human-induced factors drive morphological adaptation in Diptychus maculatus.

## Key findings

- 34 morphological traits showed significant differences among five populations of Diptychus maculatus.
- PCA explained 87.3% of the variance in morphological traits, highlighting adaptations to body energy, feeding, and sensory functions.
- Discriminant analysis achieved 90.6% accuracy in identifying key traits linked to environmental and human-induced adaptations.

## Abstract

As a typical cold‐water fish in the Schizothoracinae subfamily, Diptychus maculatus serves as an important model for understanding species adaptation through morphological differentiation and geographical environment interactions. This study characterized five geographical populations (Kizil River, Toshkan River, Muzati River, Karasu River, and Kyzyl River) in the Tarim River Basin. By integrating traditional morphology (12 traits measured with vernier calipers) and geometric morphometrics (21 landmarks), and using nonparametric tests, principal component analysis (PCA), cluster analysis (CA), and discriminant analysis (DA), we analyzed the environmental driving mechanisms of morphological variation. Results showed 34 morphological traits differed significantly (p < 0.01) among populations. The Kyzyl River population exhibited larger body size and expanded mouth cleft morphology, putatively adaptive to high altitude, low temperature, and food‐scarce feeding strategies. The Muzati River population showed greater caudal peduncle height and posterior dorsal fin origin, reflecting locomotor adaptation to rapid‐current habitats. The Kizil River population had reduced eye diameter, possibly linked to decreased visual dependence in reservoir slow‐flow environments. PCA revealed the first three components explained 87.3% of variance, reflecting body energy, cranial feeding, and sensory function modules. CA divided populations into two clades: Karasu‐Toshkan convergence due to moderate‐flow habitats, and Kizil River isolation. DA achieved 90.6% accuracy, identifying 19 key traits (e.g., interorbital distance, caudal peduncle height). This study reveals environmental and human‐induced (e.g., reservoir blockage) morphological adaptation, providing insights for plateau cold‐water fish research.

This study morphologically analyzed 385 Diptychus maculatus from 5 Tarim River Basin populations. Using traditional and geometric morphometrics, it revealed environmental (high‐altitude cold, rapids, reservoir flows) and human‐driven morphological differentiation. 34 traits varied significantly, PCA explained 87.3% of variation, discriminant analysis achieved 90.6% accuracy, aiding plateau cold‐water fish adaptive evolution research and conservation.