Abstract
Primula beesiana is a perennial herbaceous plant predominantly distributed in the alpine wetland regions of Yunnan Province, China. This species faces dual threats from habitat fragmentation and climate change, but research into its genetic background is severely lacking. Consequently, systematic analysis of the genetic diversity and population structure of Primula beesiana is crucial in formulating scientific conservation strategies. In this study, 86 individuals from six natural populations in Lijiang City, Yunnan Province, were collected and genotyped using double-digest restriction site-associated DNA sequencing (ddRAD-seq). A total of 1537 high-quality SNP loci were identified and used for genetic diversity, principal component (PCA), population structure (STRUCTURE), and gene flow analyses. Analysis of base substitutions revealed twelve mutation types, with transversions accounting for 67.9% and a transition/transversion ratio (Ti/Tv) of 0.47, potentially indicating strong environmental selection pressure. Although high overall genetic diversity was observed, significant genetic differentiation may exist among populations (Fst = 0.0056-0.0407), with heterozygote deficiency detected across all populations. Genetic structure analyses consistently grouped the six populations into four distinct clusters. Populations MDJ, WH, and HS each formed independent clusters, exhibiting clear genetic isolation, whereas XHC2, XHC1, and NX clustered together, showing high genetic similarity and frequent gene flow. Mantel tests demonstrated a significant positive correlation between genetic and geographical distances (r = 0.854, p < 0.01), supporting an isolation-by-distance model. Gene flow estimates varied considerably among populations (5.90-44.69) and decreased with increasing geographical distance. This study provides the first genomic-level evidence of significant genetic differentiation and isolation based on distance in Primula beesiana populations, offering crucial scientific support in identifying evolutionarily significant units and developing zoned conservation management strategies for this species.