Phylogeography and chromosome number variation in Micranthes nelsoniana and related species (Saxifragaceae) in Northeast Asia.

This article focuses on the phylogeography, genetic diversity, and hybridization of *Micranthes nelsoniana* and its closely related species in Northeast Asia, particularly around the Kuril Islands. Using nuclear internal transcribed spacer (ITS) and chloroplast DNA (cpDNA) sequence analyses, the study identified distinct genetic groups corresponding to continental Arctic–Asian populations and marginal island populations, including highland, Kuril–Aleutian, southern Kuril, Japanese archipelago, and Primorye clades. Evidence of hybridization was found between *M. nelsoniana*, *M. fusca*, and *M. ohwii*, with chromosome numbers (notably 2n = 24 and 50) facilitating interspecific gene flow. Cloning of high-chromosome-count plants from Hokkaido revealed mixed genetic origins from both continental and marginal groups, highlighting the significant role of marginal islands in shaping the genetic structure and diversity of these species.