ITS Sequence Variation and ITS2-Based Phylogenetic Analysis of Lesser Burnet (Sanguisorba minor Scop.) from Erzurum, Türkiye

Sanguisorba minor Scop. is a perennial forage species whose regional germplasm can be characterized using nuclear ribosomal sequence data. This study examined ITS sequence variation in an Erzurum collection and assessed the scope of single-locus inference. Extracted ITS2 sequences were evaluated using Bayesian and maximum-likelihood phylogenetic analyses and single-locus species delimitation. Separate ITS datasets were used for sequence diversity and pairwise distance analyses, and exploratory STRUCTURE clustering included 40 individuals. The primary diversity analysis included 40 study accessions, retained after excluding Sm2 and Sm11 due to insufficient sequence length and poor-quality raw sequencing reads. Across 545 sites retained by complete deletion, 16 haplotypes were identified, with haplotype diversity of 0.6154 and nucleotide diversity of 0.007789. The predominant haplotype comprised 25 sequences (62.5%), and each of the remaining haplotypes occurred once. Diversity estimates varied with sequence coverage and gap treatment. Full-ITS p-distances among the 40 Sm-coded samples in the distance dataset ranged from 0.00278 to 0.06863, with a mean of 0.02845. Exploratory clustering produced a dominant ΔK peak at K = 2, whereas mean LnP(K) was highest at K = 4. At K = 2, 31 individuals had higher membership in one cluster and nine in the other, with intermediate profiles in some individuals. These results describe ITS sequence variation in the analyzed collection but do not establish reliable separation of S. minor from the included congeners. Diversity estimates were sensitive to alignment coverage and gap treatment, while exploratory clustering requires further assessment for potential effects of read direction and missing data. The findings do not establish demographic admixture, gene flow, or environmental adaptation. Quality-controlled sequences, independent loci, and broader taxon sampling are required to evaluate the biological significance of the observed patterns.