Carex jianfengensis (Carex sect. Rhomboidales, Cyperaceae), a New Species from Hainan, China

A new species of Carex sect. Rhomboidales, C. jianfengensis, is described and illustrated from Hainan, China. The new species is similar to C. zunyiensis but differs in having involucral bracts sparsely hispid and with ca.1 cm long sheaths; inflorescence with 4 spikes, terminal spike ca. 2.5 cm long, lateral spikes 2–3.5 × 0.7–1 cm; staminate glumes narrowly ovate, ca. 5 mm; pistillate glumes triangular-lanceolate, 5–7 mm; perigynia 6–8 × 3 mm and pubescent on veins; nutlet 4–5 mm long, rhombic-ovoid, trigonous, base with shortly stipitate, apex abruptly contracted into a erect short beak, and not expanding into an annulate orifice.

The genus Carex is clearly distinguished from other genera of the Cyperaceae in having consistently unisexual flowers and a perigynium, the latter a sac-like structure of prophyllar origin that surrounds the naked gynoecium [19]. Carex has been divided into subgenera in a number of ways based on the following characters: stigma number, inflorescence structure and distribution of staminate and pistillate flowers within the spikes. The most influential classification was that of Georg Kükenthal who recognized four subgenera: Carex subg. Carex, C. subg. Indocarex, C. subg. Vignea and C. subg. Primocarex. Subsequently, C. subg. Indocarex and C. subg. Primocarex were reclassified as C. subg. Vigneastra [20]. This classification was widely followed by most authors [2,[21][22][23][24][25].
Carex sect. Rhomboidales belongs to C. subg. Carex and is characterized by long-sheathing bracts with short blades, trigonous, rhombic to ovoid perigynia with columniform bidentate beaks at the apex, and obovoid or ovoid, trigonous nutlets that are constricted in the middle part and mitrate or hastate at the apex [5,20]. The section consists of 41 species, mainly distributed in eastern Asia, with 36 species being native to China and 4 species in Hainan Island. [2, 7-9,11-14,16, 21,26-28,]. Hainan Island is located at the southern part of China, at the northern edge of tropical Asia, with about 4 100 vascular plant species. To date, 27 species of Carex have been reported from Hainan [6,14-16,29,].
During an investigation of the flora of Jianfeng Ling Nature Reserve in 2014, a novel species of Carex was collected and is here recognized as a new species in sect. Rhomboidales. Morphologically, the new species has affinities with Carex zunyiensis Tang & F.T. Wang.

Ethics statement
The new species reported in this work is collected from Jianfeng Ling Nature Reserve which is protected by the Forestry Bureau of Hainan. Permissions to visit location and field activities were obtained from Jianfeng Ling Nature Reserve Administration Bureau.

Morphological observations
The morphological description is based on examination of fresh and dried specimens. Details of the staminate terminal spike, the pistillate lateral spikes, the pistillate glume, the perigynium and the nutlet were examined and photographed under a stereomicroscope (Olympus SZX16-6156). The shapes of perigynium and nutlet were observed using a Philips XL-30E scanning electron microscope. The studied specimens (one holotype, four isotypes, two paratypes) were deposited in the herbaria of the South China Botanical Garden, the Chinese Academy of Sciences (IBSC), and the Tropical Crops Genetic Resources Institute, Chinese Academy of Tropical Agricultural Sciences (TCGRI; not listed in Thiers 2008 [30]).

Nomenclatural Acts
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Results
The new species is most similar to C. zunyiensis based on the shape of the leaves, the very short culms and the subbasal and approximate spikes, but differs sufficiently to be recognized as a new species in morphological features (

Distribution and Habitat
Carex jianfengensis was collected from Jianfeng Ling Nature Reserve, Hainan, China. It grows under the tropical mountain rain forest at altitudes of 700-900 m. Associates include Polyspora Table 1. Morphological comparison between Carex jianfengensis and C. zunyiensis. (Figs 1 and 2).

Phenology
Flowering occurs from January and usually seeds mature in March to May.

Etymology
The epithet "jianfengensis" refers to the type locality, Jianfeng Ling Natural Reserve.

Conservation status
So far, this species is known from only one population and comprises approximately 2800 caespitose individuals, covers an area of 1000 m 2 . According to the IUCN (2001) category and criteria, Carex jianfengensis is a vulnerable species (VU).

Relationships
The new species belongs to Carex sect.  [14,16]. In addition to the  Simpson & C.Z. Zheng [9,[11][12][13]26]. However, C. jianfengensis can be easily distinguished from species mentioned above by its short culms less than 5 cm and its subbasal and approximate spikes. It is similar to C. zunyiensis based on the short culms, but differs have been mentioned in above Table 1.