Intraspecific Karyotypic Differentiation in the Lycoris aurea Complex Revealed by Fluorochrome Banding and rDNA Fluorescence In Situ Hybridization

The Lycoris aurea (L’Hér.) Herb. complex—valued for its medicinal properties and horticultural applications—is characterized by extensive intraspecific dysploidy. However, a comprehensive molecular cytogenetic framework elucidating intraspecific karyotypic differentiation and the underlying evolutionary mechanisms has yet to be established. By integrating fluorochrome banding with 5S and 45S rDNA fluorescence in situ hybridization (FISH), we performed a comparative molecular cytogenetic karyotyping of 20 natural populations and synthesized these results with previously published cytogenetic data to conduct a rigorous cytogeographic analysis of this species complex. Three distinct cytotypes were identified: cytotype A (2n = 14), cytotype B (2n = 15), and cytotype C (2n = 16). Both multivariate karyomorphometric analyses and comparison of DAPI banding and rDNA FISH patterns revealed high inter-population karyotypic uniformity in cytotype A, yet pronounced intra-cytotypic karyotypic polymorphism in cytotype C. Integrated cytogenetic evidence supports a working hypothesis wherein cytotype C likely represents the ancestral karyotype, while cytotypes A and B appear to have originated from cytotype C through two and one Robertsonian fusion events, respectively—thereby implying two independent, parallel evolutionary pathways: C → A and C → B. The evolutionary biogeographic framework for this species complex—derived from hypothesis-generating integrative inference—proposes that Quaternary climate oscillations, topographic barriers, and ecological niche divergence may have acted synergistically to shape the current parapatric distribution pattern of the three cytotypes.