Molecular Insights into the Genetic Diversity, Population Structure, and Evolutionary Relationships of Populus × canescens (Aiton) Sm. in Western Kazakhstan

Populus × canescens (Aiton) Sm. is a natural hybrid between Populus alba L. and Populus tremula L., but its genetic diversity and population structure in Western Kazakhstan remain poorly characterized. Here, we investigated 12 individuals representing five geographically separated populations in the West Kazakhstan Region using chloroplast matK and rbcL sequences. The concatenated 1318 bp dataset was analyzed to assess genetic diversity, haplotype relationships, population differentiation, demographic history, and phylogenetic relationships. Seven haplotypes were identified, with relatively high haplotype diversity but low nucleotide diversity. The predominant haplotype was shared among four populations, whereas several population-specific haplotypes were detected. Pairwise nucleotide divergence ranged from 0.000635 to 0.002096, with the highest value observed between Pop4 and Pop5. Significant negative Tajima’s D and Fu and Li’s statistics were detected; however, the predominantly unimodal mismatch distribution was interpreted cautiously because the low nucleotide diversity and limited sample size reduced its sensitivity for demographic inference. Therefore, the observed pattern should not be considered conclusive evidence of demographic expansion. Bayesian phylogenetic analysis revealed heterogeneous placement of P. × canescens individuals relative to P. alba and P. tremula. These findings provide the first molecular baseline for P. × canescens in Western Kazakhstan and contribute to understanding its chloroplast genetic diversity, population structure, and evolutionary relationships.