Ploidy Analysis of Two Lineages Within the Histiopteris incisa Complex in the Japanese Archipelago

In this study, we demonstrate the new base number of Histiopteris as x = 47, rather than previously reported x = 48, based on the observed chromosome numbers of 2n = 94 and 188 for Histiopteris incisa, representing the diploid and tetraploid states, respectively. Ploidy level analysis conducted in Japan reveals that all examined individuals of the “α” lineage, which is one of the two DNA lineages within this species, are tetraploid, whereas both diploid and tetraploid individuals are observed in the “β” lineage. Notably, tetraploid individuals of the β lineage are exclusively found in Yakushima, while diploid individuals are prevalent at other collection sites. Examination of herbarium specimens indicates that the localities of each DNA lineage of the specimens, which are identified based on morphological traits, correspond entirely to the localities of the α and β lineages of currently existing populations.