The meiotic chromosome numbers of the species vary, n = 43_II, 44_II, 45 _II. The counts are incongruent with previous reports from Korean populations, 2n = 66, 72 (Chung and Im, 2018), 2n = 84 (Chung et al., 2018); and a Japanese population, 2n = 90 (Tanaka, 1948). The species has been considered as a Japanese endemic, but recently distributions of the species in Japan and Korea have been known (Im et al., 2008; Hoshino et al., 2011; Park et al., 2016). Although C. miyabei is distinctly characterized pubescent perigynia with long beaks, and pistillate scales with aristate apexes, the species has been often confused with C. glabrescens (Kük) Ohwi for similarity on female spike numbers (more than two), and sharing ecological habitats (Im et al., 2008). These species occur throughout South Korea, but the latter grows mainly middle parts of South Korea (Park et al., 2016). Because both favor sunny, sandy places along rivers, it is not hard to find populations of the two taxa close each other (Im et al., 2008; Park et al., 2016). Variations in morphological characters such as perigynium shapes and surface features have made it hard to distinguish them from each other. Chromosome numbers of C. glabrescens have not been reported. As proposed in the previous studies (Chung and Im, 2018; Chung et al., 2018), taxonomic and cytological research should be conducted to understand the two morphologically challenging taxa in the section with taxon sampling covering the distribution areas of the taxa.

The meiotic chromosomes of C. metallica from a Korean population is observed for the first time, n = 30_II, which is identical to a previous report from Japan (Hoshino et al., 2011). The species only occurs in Jeju Island, South Korea and is mainly distributed in southern parts of China and Japan (Park et al., 2016; Chen and Zhang, 2018; Masaki, 2018). Dai et al. (2010) reported distributions of the species in Fujian (China) and Taiwan. The Hymenochlaenae comprised of about 60 species in Africa, Asia, and Central and North America, and Europe, and many Asian species exhibit narrow distribution patterns (Dai et al., 2010). Thirteen taxa out of fifteen Chinese species in the section are endemic to China, and C. hondoensis Ohwi occurs only in Japan (Dai et al., 2010; Hoshino et al., 2011).

Chromosome number of n = 33_II for C. fernaldiana is identified, which is the first report on the taxon from a Korean population. In Japanese populations, the species exhibits a range of chromosome number variations, 2n = 66–74 (Tanaka, 1948; Hoshino et al., 2011). Although the species is distinguished from closely related taxa such as C. stenostachys Franch. et Sav. and C. polyschoena by long rhizomes and glabrous perigynia (Park et al., 2016; Nam, 2017), C. fernaldiana is considered as a synonym of C. pisformis Bott (Govaerts, 2019). Govaerts (2019) lists homotypic names of C. fernaldiana: C. sachalinensis var. fernaldiana (H. Lév. & Vaniot) T. Koyama, C. pisiformis var. fernaldiana (H. Lév. & Vaniot) T. Koyama, and C. sachalinensis subsp. fernaldiana (H. Lév. & Vaniot) T. Koyama. Nomenclatural synonyms need to be reevaluated. The evaluation should be conducted along with examinations on taxonomic synonyms covering the distribution areas of C. fernaldiana and C. pisiformis complex.

For the first time, chromosome number of C. appendiculata from a Korean population is revealed, n = 27_II. Previously, 2n = 76 and c. 80 were reported from Russia (Krogulevich, 1976; Zhukova and Petrovsky, 1976). The species is mainly distributed in northern areas of South Korea and is characterized with 1–2 terminal female spikes and broad perigynia (Park et al., 2016). Although taxonomic status and delimitation are not congruent among distributed countries, the species occurs in China (north east), Japan (north), Russia (east), and Korea (north) (Dai et al., 2010; Hoshino et al., 2011, Ji, 2013; Park et al., 2016; Chen and Zhang, 2018; Masaki, 2018).

Counts on three taxa are the first reports from Korean populations: Carex appendiculata (Trautv. & C. A. Mey.) Kük. (n = 27_II), C. fernaldiana H. Lév. & Vaniot (n = 33_II), and C. metallica H.Lév. (n = 15_II). The reports on the other species increase a range of variation in chromosome number within a taxon: C. miyabei Franch. (n = 43_II, 44_II, 45_II). The counts confirm that chromosome number variations within and/or among taxa resulted from aneuploidy/agmatoploidy, and connote high species diversity in Carex. The report updates chromosome number inventory on Korean Carex to 24 taxa out of 180 taxa. Accumulating chromosome number data in Carex contributes to understanding species diversity of the genus.