Summary Chromosome numbers of seven Carex taxa collected from the Korean peninsula are reported. This study is the first observations of meiotic chromosomes for Carex species from Korean populations. A univalent is observed in C. ischnostachya Steud. var. fastigiata T. Koyama (n=26II+I), and two different chromosome numbers are observed in an individual of C. leucochlora Bunge (n= 27II, 29II). For the first time, the chromosome number for C. polyschoena H. Lév. & Vaniot (n=26II) is reported here. The results of diverse chromosome numbers suggest that polyploidy and aneuploidy including agmatoploidy and symploidy (increases and decreases in chromosome number due to fission or fusion, respectively) have played an important role for Carex species diversity in Korea.

Carex L. is one of the most species-rich genera in the flora of Korea with about 157 taxa. Somatic or meiotic chromosome numbers of eight Carex taxa from the Korean Peninsula are reported, including first counts for C. macrandrolepis H. Lév. (n=37II) and C. splendentissima U. Kang & J. M. Chung (2n=12). Furthermore, there are first chromosomal investigations from Korea populations: C. bostrychostigma Maxim. (n=22II), C. capricornis Meinsh. ex Maxim. (n=35II), and C. breviculmis R. Br. (n=33II). None of the chromosomes has distinct primary constrictions. Carex sect. Mitratae exhibits high variation in chromosome numbers with aneuploidy (chromosome number increases with genomic duplication) and/or agmatoploidy (chromosome number increases without genomic duplication) whereas C. sect. Siderostictae shows polyploidy. Chromosome dynamics have played an important role in Carex species diversity in the Korean Peninsula.

Due to substantial population decline, the Korean orchid P . scolopendrifolia is considered endangered and highly threatened. Like many endangered species, it is vulnerable to biological and anthropogenic threats that can lead to the loss of genetic diversity and, ultimately, extinction. Therefore, the assessment of genetic diversity and population genetic structure is imperative for conservation. In this study, we newly developed 15 polymorphic microsatellite markers. Analyses of genetic diversity and population genetic structure that included 182 samples from 11 populations were conducted using microsatellite markers and four noncoding regions of chloroplast DNA. Our study revealed a relatively low level of genetic diversity ( Ho = 0.529, He = 0.356), albeit harboring with private alleles based on microsatellite genotyping data, and high haplotype diversities based on chloroplast DNA sequences data. The results of STRUCTURE and PCoA based on microsatellite genotyping data showed population differentiations. An AMOVA based on chloroplast DNA sequence data further corroborated these conclusions, indicating about 70% of variations found among populations. Low genetic diversity and divergence among the population might have been caused by factors, such as asexual reproduction, demographic events (bottleneck and population expansion), geographic isolation, and low gene flow. The development and implication of conservation strategies and management of P . scolopendrifolia are proposed based on these results.

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The meiotic chromosome numbers of six Carex species in three sections are counted; C. miyabei Franch. (n=42 II ) in sect. Carex, C. breviculmis R. Br. (n=31 II , 32 II , 33 II ), C. polyschoena H. Lév. & Vaniot (n=36 II , 37 II ), C. sabynensis Less. ex Kunth (n=27 II , 28 II ) in sect. Mitratae Kük., and C. heterolepis Bunge (n=37 II , 38 II , 40 II ) and C. forficula Franch. & Sav. (n=25 II , 27 II ) in sect. Phacocystis Dumort. The chromosome counts for C. miyabei, C. heterolepis, and C. forficula from Korean populations are verified for the first time.Considered with previous reports, all the species exhibit variations in chromosome number from n=4 to n=36. Contiguous variation in chromosome numbers and non-constricted meiotic chromosomes with holocentromeric nature suggest that aneuploidy and/or agmatoploidy and/or symploidy should have played an important role in the sections.