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Micranthes nelsoniana possesses multiple different variants and numerous chromosomes. Based on the internal transcribed spacer (ITS) and chloroplast (cp)DNA sequences, the phylogeography of M. nelsoniana and its relatives in Northeast Asia was investigated, with extensive sampling around the Kuril Islands. The Arctic–Asian continent and a clade of marginal islands were the two main groupings that comprised the ITS phylogenetic tree. The island clade was separated into five well-supported clades: Kamchatka and Hokkaido highlands, Kuril–Aleutian Islands, southern Kuril Islands, Japanese archipelago, and Primorye region. Micranthes fusca was found in Japan and in the southern Kuril Islands. It is a separate species that created several types of hybrids between M. nelsoniana in the centre of the Kuril Islands based on a comparison of the ITS and cpDNA networks. Micranthes nelsoniana and M. ohwii appear to have hybridized in the northern Kuril Islands. Cytological investigation on the local species of M. nelsoniana showed that the chromosomal numbers are: 2 n  = 24, 26, 28, 30, 50, and 80. Among them, two usual numbers to this area, 2 n  = 24 and 50, appear to encourage interspecific gene exchange. The genomes of Hokkaido plants with high chromosome counts were cloned, revealing that they contained genes of both continental and marginal origins. This study revealed the crucial role of marginal islands along Northeast Asia in the genetic diversity of M. nelsoniana and related species. [ABSTRACT FROM AUTHOR]

Commonly considered bispecific, Acorus is one of the most phylogenetically isolated angiosperm genera that forms the order Acorales sister to the rest of the monocots. The Acorus calamus group is widely distributed in the Holarctic regions of Eurasia and America and has strong medicinal and other practical uses since prehistoric times. Earlier studies interpreted native diploids and invasive triploids occurring in North America as two species that differed in morphology and distribution ranges. In contrast, diploids, triploids, and tetraploids occurring in Eurasia are commonly interpreted as one species because they reportedly cannot be distinguished in collections. We resolve the controversy over taxonomic concepts between Eurasia and America and provide the first detailed multidisciplinary account of Acorus in temperate Asia. We used plastid and nuclear markers, leaf anatomy, seed micromorphology, pollen stainability, flow cytometry, and direct chromosome counts. Diploids and tetraploids show stable molecular and micromorphological differences. Triploids are their sterile hybrids, with the plastid genome inherited from the diploid parent. Diploids of America and Asia tend to differ in leaf characters. Coadaptative coexistence with pollinating beetles Platamartus jakowlewi and Sibirhelus corpulentus (Kateretidae) is conserved between diploids and tetraploids and over a distance of 4700 km between Japan and Western Siberia. Diploids are self‐compatible and can set seeds in the absence of kateretid beetles. Tetraploids are self‐incompatible and/or cannot set seeds in the absence of Platamartus and Sibirhelus. Diploids (A. americanus) and tetraploids (A. verus) are two biological species; the former has two subspecies. Acorus calamus should be restricted to triploids; it apparently first evolved in temperate Asia. Diploids mostly occur in much cooler climates than triploids and tetraploids. Accessions of A. verus and A. calamus from tropical Asia are apparently derived from ancient introductions. Our data provide a new framework for the pharmacological use of Acorus. [ABSTRACT FROM AUTHOR]