Hyeonjin KimP, Bokyung Choi, Tae-Soo Jang

Department of Biological Science, Chungnam National University, Daejeon 34134, Korea

The genus Veratrum L. (Melanthiaceae), consisting of sections Veratrum and Fuscoveratrum, is widely distributed across the Northern Hemisphere. Reflecting different taxonomic perspectives, the genus includes between 16 and 48 taxa, as continuous morphological variation complicates interspecific delimitation. This study examined 11 Veratrum taxa native to Korea and Japan using scanning electron microscopy for micromorphological analyses, molecular phylogenetic analyses based on ITS, matK, trnL–F, and psbA–trnH, karyotype and genome size estimation, and fluorescence in situ hybridisation, with the aim of identifying informative diagnostic characters and reassessing taxonomic boundaries. As a result of microscopic investigation and molecular phylogenetics, leaf micromorphological characters (trichomes and calcium oxalate crystal) and molecular phylogenetics analyses supported the current sectional classification, although interspecific resolution remained limited. In contrast, pollen and orbicule micromorphology showed limited variation and low taxonomic resolution. Cytogenetic analysis reveals that section Veratrum is tetraploid (2n = 4x = 32; 3.58 ± 0.12 pg/1C), while section Fuscoveratrum is diploid (2n = 2x = 16; 2.21 ± 0.38 pg/1C). These differences are mirrored in stomatal and pollen sizes, which serve as reliable micromorphological markers for ploidy levels. Notably, V. nigrum (section Fuscoveratrum) is distinguished by its broadly elliptical leaves, short pedicels, and a unique cytogenetics traits (2.95 ± 0.12 pg/1C; haploid karyotype length 41.95 μm), confirming these as diagnostic characters. This integrative study highlights the necessity of molecular cytogenetic data for clarifying the evolutionary and taxonomic framework of the genus.