Profiling Genetic Variation: Divergence Patterns and Population Structure of Thailand's Endangered <em>Celastrus paniculatus</em> Willd

This study examined genetic diversity in the endangered medicinal plant Celastrus paniculatus across northern and northeastern Thailand to inform conservation strategies. Analysis of nuclear internal transcribed spacer (ITS) and ribulose-1,5-bisphosphate carboxylase/oxygenase large subunit (rbcL) markers in seven populations revealed 17 haplotypes (CpI1–CpI17), with 15 being population-specific. Genetic diversity varied significantly among populations: CMI showed the highest diversity (Hd = 0.944±0.070) while LEI and LPN displayed complete homogeneity. The haplotype network identified a central shared haplotype (CpI4), suggesting common ancestry, with the PLK population showing distinct genetic divergence through unique haplotypes separated by multiple mutation steps. Genetic distance calculations revealed close relationships between LEI and NPM populations (distance = 0.0004), with greater differentiation between PLK and other populations (distances &amp;gt; 0.005). Phylogenetic analyses confirmed species integrity while highlighting population clusters, especially PLK in ITS analyses and LPN in rbcL analyses. This genetic structure information provides a foundation for targeted conservation planning. Results suggest that conservation efforts should prioritize both genetically diverse populations (like CMI and MKM) and genetically distinct ones (like PLK) to preserve maximum evolutionary potential. This study delivers crucial molecular data for developing evidence-based conservation strategies to protect this valuable medicinal species from further decline.