Carex malipoensis, a new species from southeast Yunnan, China, is here described and illustrated. It is morphologically similar to C. trichophylla in sect. Euprepes, but differs from it by its longer inflorescences and peduncles, pendulous spikes, hispidulous female glumes, densely hispidulous utricles, and longer nutlets.

Carex sect. Euprepes, Carex trichophylla, morphology, taxonomy

As one of the largest angiosperm genera, Carex Linnaeus (1753) (Cyperaceae) comprises an extremely high diversity of about 2000 species (Roalson et al. 2021; WCSP 2021). The genus has a Cosmopolitan distribution. It was placed within the tribe Cariceae and divided into four subgenera by Kükenthal (1909): subg. Psyllophora (Degland 1828) Petermann (1849), subg. Vigneastra (Tuckerman 1843) Kükenthal (1899), subg. Vignea (P. Beauv. ex Lestiboudois 1819) Petermann (1849) and subg. Carex. This classification of Kükenthal had been widely adopted by subsequent researchers for a long time. Recent molecular phylogenetic studies revealed that Cariceae is a natural group, and the previously recognized genera of this tribe, i.e., Cymophyllus Mack. ex Britton & A.Br., Kobresia Willdenow, Schoenoxiphium Nees von Esenbeck, and Uncinia Persoon, should be merged into Carex (Yen and Olmstead 2000; Global Carex Group 2015; Starr et al. 2015; Léveillé-Bourret et al. 2018; Martín‐Bravo et al. 2019; Villaverde et al. 2020; Larridon et al. 2021; Roalson et al. 2021). A framework of the combined giant genus was urgently needed to increase our understanding of Carex. In order to solve this problem, Villaverde et al. (2020) conducted a robust phylogeny of Carex based on molecular data (308 nuclear exon matrices, 543 nuclear intron matrices and 66 plastid exon matrices) and six clades were recognized. Accordingly, Villaverde et al. (2020) proposed an updated infrageneric classification of Carex and classified it into six subgenera: subg. Siderosticta M.J. Waterway, subg. Carex, subg. Euthyceras., subg. Psyllophorae, subg. Uncinia (Pers.) Peterm. and subg. Vignea. However, the classification within the subgenera still remained unresolved, so a more systematic and friendly infrageneric classification system was required. A framework infrageneric classification of Carex was proposed recently which divided Carex into 62 formally named Linnean sections and 49 informal groups based on the current phylogenetic knowledge of Carex (Roalson et al. 2021).

A total of 527 Carex were recorded in Flora of China (Dai et al. 2010), the Catalogue of Life China (Chen and Zhang 2018) recorded 593 species, which represents the most complete and update list of the genus in China. The number of species of Carex continues growing in China as more new species have been reported in recent years (Lu and Jin 2018; Zhang et al. 2018; Jin et al. 2020; Lu et al. 2020; Yang and Liu 2020).

During our field investigations between 2016 and 2018, we collected specimens of an unknown species of Carex in Malipo County, southeast Yunnan Province, China. After careful morphological studies, examination of herbarium specimens and relevant literature, we concluded that it can be assigned to Carex sect. Euprepes based on a combination of some morphological characters: cauline leaves well-developed; leaf blades and involucral bracts elliptic to linear-elliptic, with prominent transverse veins; complex branched inflorescence; spikes androgynous; and presence of utriculiform cladoprophylls (Jiménez-Mejíias et al. 2016) at the base of spikes. Molecular phylogenetic studies indicated that C. sect. Euprepes belongs to the core Carex clade (Starr et al. 2015; Villaverde et al. 2020), and the most recent infrageneric classification framework placed it with the Indica Clade together with species traditionally placed in sections Euprepes and Mapaniifoliae (Roalson et al. 2021). Consisting of seven species, sect. Euprepes are restricted to South and Southeast Asia (Nelmes 1955). Only one species of the section, C. zizaniifolia Raymond (1959), was previously reported from China, distributed in southeast Yunnan Province (Dai et al. 2010; Chen and Zhang 2018). However, after our research on this section, we conclude that our new collections are different from all known species and represent a species new to science. We describe and illustrate it here below.

The new species was compared morphologically with specimens of other taxa of Carex sect. Euprepes from the following public herbaria A, BM, E, GH, HNU, IBSC, K, KUN, HUH, MO, MT, NY, P, PE, and US [acronyms follow Theirs (continuously updated)] as well as our new collections across China (especially with material collected from southeast Yunnan and neighboring area; herbarium specimens kept in KUN). Meanwhile, protologues and other related taxonomic literature were collated and reviewed. The characters’ data come from specimens measurements and the prologue (C. atrivaginata Nelmes and C. tricophylla Nelmes (1955), C. euprepes Nelmes and C. laosensis Nelmes (1939), C. tavoyensis Nelmes (1948), C. zizaniifolia Raymond and C. poilanei Raymond (1959)). The terminology used by Kükenthal (1909) for the morphological description of Carex species was adopted here. The distribution of the new species was compiled from the herbarium specimen records and our own collections, and shown on the distribution map.

A detailed morphological comparison of the potential new species and the seven species of C. sect. Euprepres is summarized in Table 1. Morphologically, the new species is most similar to C. tricophylla but can be distinguished by the characteristics of culms (70–105 cm long, 2–4 mm thick, sides ribbed in the new species vs. culms 45–65 cm long, 1–1.5 mm thick, sides concave in C. tricophylla); leaf sheaths (1.5–7 cm long vs. 1.2–2 cm long); inflorescences (20–45 cm long, peduncles up to 9 cm long vs. 3–15 cm long, more or less exserted), spikes (15–33 mm long, pendulous vs. 7–10 mm long, erect), female glumes (hispidulous vs. glabrous), utricles (densely hispidulous vs. glabrous below, adpressed-hispid above), and nutlets (4–4.5 mm long vs. 2.25–2.5 mm long). The new taxon can be distinguished from all the other seven species in this section by their culms (length, cross-sectional shape, sides and indumentum); leaves (shape, transverse veins), sheath (length, indumentum and the appendage of mouth); inflorescence bigger (20–45 × 3–5 cm in the new taxa vs. 3–25 × 1–5 cm in the other species) or with different shape (oblong in the new taxon vs. oblong, narrowly oblong or triangular-ovate in other species); peduncles longer (up to 9 cm long in the new taxon vs. scarcely or slightly exserted in other species; only C. atrivaginata has relative long peduncles not exceeding 5 cm); and the female glumes, utricles and nutlets (differences in shape, size and indumentum).

In comparison with other species of C. sect. Euprepes, C. malipoensis is morphologically most similar to C. trichophylla. Both species have obtusely trigonous culms and elliptic and subpetioleate leaf blades, inflorescences big and loose, and utricles longer than 6 mm, all characters that differ from all the remaining species of C. sect. Euprepes. Despite their shared similarities, C. malipoensis can be distinguished from C. trichophylla in the length of inflorescences and peduncles, and indumentum of sheath and utricles. Specifically, C. malipoensis has much longer culms and spikes, and larger leaves, panicles, and achenes compared with that of C. trichophylla. Moreover, the female glumes and utricles are hispidulous in C. malipoensis, but glabrous in C. trichophylla.

We would like to thank Dr. Chun-Lei Xiang and two anonymous reviewers for their constructive suggestions that greatly improved this paper. We are grateful to the staff of herbaria IBSC, KUN and PE for their kind assistance with research facilities. We also thank Dr. Xin-Xin Zhu for providing the photographs of the new species. This work was supported by the National Natural Science Foundation of China (Grant No. 31872649).