Sedum diversiflorum sp. nov. (Crassulaceae), a new species with variable merosity from the Satsunan Islands, Kagoshima, Japan

We re‐examined the taxonomic status of a plant previously identified as Sedum formosanum subsp. formosanum from four islands in the Satsunan Islands, Japan. To clarify its taxonomic identity, we conducted morphological and phenological comparisons and performed molecular phylogenetic analyses based on nuclear internal transcribed spacer (ITS) and three chloroplast DNA regions using closely related species of Sedum in East Asia. Morphologically, the plants share traits with S. danjoense , S. formosanum subsp. formosanum , S. formosanum subsp. miyakojimense , S. plumbizincicola and S. tetractinum , but differ in key features such as their perennial life cycle, greenish to yellowish stem, presence of lateral branches, spatulate leaves with rounded apices, variation in sepal shape, yellow anthers, oblique fruits and autumnal flowering (October–December). Notably, the plants exhibit remarkable variation in floral merosity – in the number of petal, stamen, and pistils – a unique trait absent in other East Asian Sedum species. Phylogenetic analyses revealed inconsistency between the nuclear ITS tree and the chloroplast DNA tree: the nuclear ITS tree clustered the plants with S. danjoense , whereas the chloroplast DNA tree grouped them with S. formosanum subsp. miyakojimense . This finding suggests that the plants experienced chloroplast capture due to introgressive hybridization between the two species. Considering their distinct morphological, phenological and genetic features, we described these plants as a new species, Sedum diversiflorum .