A taxonomic revision of the rare genus <i>Pentactina</i> (Rosaceae) based on comparative phylogenetic analyses

The genus <i>Pentactina</i> (Rosaceae) has long been recognized as a rare monotypic genus endemic to Korea. The type species, <i>Pentactina rupicola</i>, is confined to small populations in the Kumgangsan Mountains of North Korea. However, a recent taxonomic study suggested a new status of <i>Pentactina schlothauerae</i> in the Russian Far East, which was formerly classified as a species of the genus Spiraea. In this study, comparative phylogenetic analyses using sequence datasets from nuclear ribosomal DNA and chloroplast genomes identified a robust sister relationship between <i>P. rupicola</i> and <i>P. schlothauerae</i> and substantiated that the genus <i>Pentactina</i> is distinct from other closely related genera. These results support the recent taxonomic reclassification of <i>P. schlothauerae</i> into the genus <i>Pentactina</i>, which discounted the taxonomic treatment of <i>Pentactina</i> as a monotypic genus endemic to Korea. Nevertheless, the oligotypic genus <i>Pentactina</i> remains crucial for biodiversity due to its distinct lineage with rare and narrowly endemic species.