Cyperaceae tribe Cariceae is characterized by both species richness and habitat diversity, making it an ideal system to study ecological specialization and niche differentiation. We present a phylogenetic hypothesis for the tribe based on nuclear and chloroplast DNA sequence comparisons (ETS-1f, ITS, trnL intron, trnL-trnF intergenic spacer) for 140 representative species from five continents, and use this hypothesis to suggest patterns of both niche conservatism and niche differentiation, particularly within the large subgenus Carex. We identify a new major clade, comprising forest species of East Asian Carex section Siderostictae (subgenus Carex) as sister to the rest of tribe Cariceae. Within Carex subgenus Carex, species tolerant of water-saturated habitats occur in only a few, apparently derived groups, with varying species richness. Clades of predominantly wetland species tend to have broad geographic distribution, often with sister species on different continents, suggesting recent dispersal. In contrast, species within several clades are predominantly forest specialists with distinct Asian and North American lineages. Niche segregation along environmental gradients, such as soil moisture or acidity, is quite common among closely related wetland species, but more difficult to demonstrate within upland forest groups. More complete sampling of species within both wetland and forest groups, combined with comparable sampling of environmental preferences and testing against null models, will be needed for more rigorous exploration of the observed patterns.

Phylogenetic studies of Carex L. (Cyperaceae) have consistently demonstrated that most subgenera and sections are para-or polyphyletic. Yet, taxonomists continue to use subgenera and sections in Carex classification. Why? The Global Carex Group (GCG) here takes the position that the historical and continued use of subgenera and sections serves to (i) organize our understanding of lineages in Carex, (ii) create an identification mechanism to break the~2000 species of Carex into manageable groups and stimulate its study, and (iii) provide a

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.

Carex (Cyperaceae), with an estimated 2000 species, nearly cosmopolitan distribution and broad range of habitats, is one of the largest angiosperm genera and the largest in the temperate zone. In this article, we provide argument and evidence for a broader circumscription of Carex to add all species currently classified in Cymophyllus (monotypic), Kobresia (c. 60 species), Schoenoxiphium (c. 15 species) and Uncinia (c. 70 species) to those currently classified as Carex. Carex and these genera comprise tribe Cariceae (subfamily Cyperoideae, Cyperaceae) and form a well‐supported monophyletic group in all molecular phylogenetic studies to date. Carex as defined here in the broad sense currently comprises at least four clades. Three are strongly supported (Siderostictae, core Vignea and core Carex), whereas the caricoid clade, which includes all the segregate genera, receives only weak to moderate support. The caricoid clade is most commonly split into two clades, one including a monophyletic Schoenoxiphium and two small clades of species of Carex s.s., and the other comprising Kobresia, Uncinia and mostly unispicate species of Carex s.s. Morphological variation is high in all but the Vignea clade, making it extremely difficult to define consistent synapomorphies for most clades. However, Carex s.l. as newly circumscribed here is clearly differentiated from the sister groups in tribe Scirpeae by the transition from bisexual flowers with a bristle perianth in the sister group to unisexual flowers without a perianth in Carex. The naked female flowers of Carex s.l. are at least partially enclosed in a flask‐shaped prophyll, termed a perigynium. Carex s.s. is not only by far the largest genus in the group, but also the earliest published name. As a result, only 72 new combinations and 58 replacement names are required to treat all of tribe Cariceae as a single genus Carex. We present the required transfers here, with synonymy, and we argue that this broader monophyletic circumscription of Carex reflects the close evolutionary relationships in the group and serves the goal of nomenclatural stability better than other possible treatments. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 179, 1–42.