Genetic Diversity and Population Structure of Wild Macrobrachium nipponense in the Pearl River Basin: A Treasury of Germplasm for Aquaculture and Conservation

This study evaluated the genetic diversity and population structure of wild M. nipponense populations in the Pearl River Basin based on mitochondrial DNA (mtDNA) D-loop sequences. A total of 14 wild populations were collected from the West River, North River, and Pearl River Delta, and genetic diversity and population differentiation were assessed using haplotype analysis, analysis of molecular variance (AMOVA), pairwise FST, and principal component analysis (PCA). A total of 351 variable sites were identified. The overall haplotype diversity (h) and nucleotide diversity (π) were 0.947 and 0.03665, respectively, indicating high genetic diversity across the Pearl River Basin. Significant genetic differentiation was detected among populations (FST = 0.3785, p-value < 0.001), with 37.85% of genetic variation occurring among populations. PCA revealed distinct genetic relationships among populations, supporting the presence of population genetic structure within the Pearl River Basin. Populations from Tian’e County, Xilin County, Dahua Yao Autonomous County, and other upper tributaries of the West River exhibited distinct genetic characteristics compared with populations from Zhaoqing City, Guiping City, Guangzhou City, and the middle and lower reaches of the West River and the Pearl River estuary. Among the 14 populations, those from Zhaoqing City, Guiping City, and Guangzhou City exhibited relatively high genetic diversity and distinctive genetic characteristics. These findings suggest that the complex hydrological structure and historical connectivity of the Pearl River Basin have contributed to the observed population genetic structure. The genetically diverse populations identified in this study represent valuable wild germplasm resources for the conservation and selective breeding of M. nipponense.