Abstract:

Aims: The Yellow River has played a crucial role in the development of Chinese civilization. However, it is now facing severe environmental challenges due to human activities, including soil erosion, water pollution, and the fragmentation of aquatic habitats. Under these circumstances, it is essential to investigate whether the aquatic organisms, particularly fish species, in the Yellow River basin have been affected. This study aimed to assess the genetic diversity and population structure of Pseudorasbora parva in the Yellow River.

Methods: In this study, we collected 153 individuals of P. parva from 15 sites across the Yellow River and sequenced their mitochondrial COI gene. Additional COI sequences from other river systems, including the Yangtze River, Pearl River, and Nujiang River, were retrieved from GenBank for comparison. Haplotype composition, haplotype diversity (h), nucleotide diversity (π), and the average number of nucleotide differences (k) were calculated. To evaluate population structure, we conducted an analysis of molecular variance (AMOVA) by grouping the Yellow River populations into upper, middle and lower reaches based on their geographical locations. Furthermore, we also performed Mantel tests, phylogenetic analyses, and Bayesian skyline plot (BSP) modeling to examine genetic differentiation and demographic history.

Results: A total of 34 polymorphic loci and 27 haplotypes were identified among the Yellow River populations. Eight haplotypes were shared with other river systems. The haplotype and nucleotide diversity of P. parva in the Yellow River were relatively high (h = 0.802 ± 0.030; π = 0.00508 ± 0.00035), suggesting a historically stable population. AMOVA results indicated that most genetic differentiation existed within populations (86.38%), with limited variation among groups (0.11%) and among populations within groups (13.51%). Genetic distances among the Yellow River populations ranged from 0.00060 to 0.00954. The Mantel test revealed no significant correlation between genetic distance and geographic distance. Phylogenetic trees and haplotype networks indicated no clear geographic structure, and neutrality tests and mismatch distributions suggested no recent population expansion. BSP analysis showed that the P. parva population experienced a slow increase from 0.175-0.005 Ma, followed by a decline to the present.

Conclusion: The P. parva populations from the Yellow River exhibited relatively high genetic diversity without significant genetic differentiation, indicating ongoing gene flow. While dam construction may pose barriers to dispersal, human-mediated activities such as aquatic trade and species introduction have likely mitigated the effects of isolation. However, population declines observed in recent history may be attributed to environmental degradation and water pollution. These findings highlight the need for enhanced conservation and ecological monitoring in the Yellow River basin.

Key words: Yellow River, Pseudorasbora parva, COI, genetic diversity, population demography