Carex diaoluoshanica (Carex sect. Lageniformes, Cyperaceae), a New Species from Hainan, China

Carex diaoluoshanica, a new species of Carex sect. Lageniformes from Hainan, China, is described and illustrated. The new species is similar to C. breviscapa but differs in having wider leaves with the leaf base gradually narrowed, 5–10 cm long and petiolelike, culms subfiliform, with only two spikes, the lateral female spikes from near the culm base.

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 [14]. The variations in the structure of the perigynium are used as the key features in Carex. This is largely due to the subtle differences in shape, size, texture and nervation, which have been used as primary characters for the delimitation of many species in Carex [15]. Carex has been divided into subgenera in a number of ways based on the characters of stigma number, inflorescence structure and the distribution of staminate and pistillate flowers within the spikes. The most influential was Georg Kükenthal's classification which recognised four subgenera: Carex subg. Carex, C. subg. Indocarex, C. subg. Vignea and C. subg. Primocarex. Subsequently, C. subg. Indocarex and C. subg. Primocarex were corrected to C. subg. Vigneastra [16]. This classification was widely followed by most authors [3,8,17,18,22,23].
Carex sect. Lageniformes (Ohwi) Nelmes belongs the core Carex clade [23]. It is characterized by having leaves longer than the culm, the terminal spike male and lateral spikes female, the female glumes oblong-ovate or obovate, the perigynium fusiform or rhombic-fusiform, the nutlet rhombic or fusiform with the apex truncate or shallowly concave, and the style base cylindric, slightly thickened, and persistent. It consists of 12 species mainly distributed in eastern and southeast Asia, with 8 species reported in China, 4 of which are endemic [3,8]. Hainan Island is located at the southern part of China, at the northern edge of tropical Asia, with about 4100 vascular plants species [19][20]. To date, 24 species of Carex have been reported from Hainan Island [8,13,21].

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

Morphological observations
Morphological description of the new species was based on examination of fresh and pressed specimens. Details of the terminal spike staminate, lateral spikes pistillate, pistillate glume, perigynium and nutlet were examined and photographed under a stereomicroscope (Olympus SZX16-6156). The Perigynium and Nutlet shape of Carex diaoluoshanica, C. breviscapa and C. longipetiolata were observed using a Philips XL-30E scanning electron microscope (SEM). The studied specimens are kept in the Herbarium of South China Botanical Garden, the Chinese Academy of Sciences (IBSC), and the Tropical Crops Genetic Resources Institute, Chinese Academy of Tropical Agricultural Sciences (TCGRI).

Nomenclatural Acts
The electronic version of this article in Portable Document Format (PDF) in a work with an ISSN or ISBN will represent a published work according to the International Code of Nomenclature for algae, fungi, and plants, and hence the new names contained in the electronic publication of a PLOS ONE article are effectively published under that Code from the electronic edition alone, so there is no longer any need to provide printed copies.
In addition, new names contained in this work have been submitted to IPNI, from where they will be made available to the Global Names Index. The IPNI LSIDs can be resolved and the associated information viewed through any standard web browser by appending the LSID contained in this publication to the prefix http://ipni.org/. The online version of this work is archived and available from the following digital repositories: PubMed Central, LOCKSS.

Results
During an investigation of the flora of Diaoluo Shan Nature Reserve in 2013, a new species belonging to Carex sect. Lageniformes was found (Fig. 1). This species is similar to C. breviscapa C. B. Clarke, but differs sufficiently to be recognized as a new species. Nine specimens (one holotype, four isotypes and four paratypes) of the studied are kept in the Herbarium of South China Botanical Garden, the Chinese Academy of Sciences (IBSC), and the Tropical Crops Genetic Resources Institute, Chinese Academy of Tropical Agricultural Sciences (TCGRI). Based on the shape of the perigynium and nutlet, the new species is most similar to Carex breviscapa, but they differ distinctly as follows (the former is new species, the latter is C. breviscapa): culms subfiliform, ca. 0.5 mm thick (culms slightly scabrid, ca. 2-5 mm thick); leaf blades 7-15 mm wide with the base attenuate and petiolelike, ca. 5-10 cm long (leaf blades 6-7 mm wide, not attenuate at base); inflorescence with just 2 spikes (inflorescence 3-5-noded, with 3-5 spikes at each node); lateral spikes 1-1.5 cm long (3-4 cm long), lateral female spike solitary, arising from near culms base and enclosed within bladeless sheaths (lateral female spikes many, arising from well above culm base).

Conservation status
The population of Carex diaoluoshanica comprises approximately 2 500 caespitose individuals, covers an area of 1 000 m 2 , at altitudes of 800-900 m. According to the IUCN (2001) category and criteria, C. diaoluoshanica is a vulnerable species(VU). Fortunately, this locality is in a remote place in the Diaoluoshan Natural Reserve. palawanensis Kük. (endemic to Philippines); C. lageniformis Nelmes and C. pleurocaula Nelmes (all endemic to Thailand). The new species is placed in C. sect. Lageniformes because its perigynium and nutlet are fusiform, and cylindric, slightly thickened and persistent style base (Fig. 1, H and J; Fig. 3, A and B). But according to observation its differ from these above-mentioned, the main difference of morphological characters beweeen C. diaoluoshanica and its related species see the identification key. In Hainan Island, two members of this section, C. breviscapa and C. truncatigluma were recorded previously. The new species can be easily distinguished from these by the petiolelike leaf base 5-10 cm long, and the subfiliform culm with only 2 spikes. C. diaoluoshanica is most closely related to C. breviscapa by characters of the perigynium: longer than the female glumes, fusiform, obscurely trigonous, minutely pubescent, many-veined, and with the base cuneate and stipitate, but it differs from by the subfiliform culms, wider leafblade with a petiolelike base and by having only 1 lateral female spike inserted near the culm base. In addition, the species Carex longipetiolata Q.L. Wang, H.B. Yang & Y.F. Deng is also recorded from Diaoluo Shan Nature Reserve [13]. This is similar to C. diaoluoshanica because it also has a petiolelike leaf base. However, C. longipetiolata belongs to Carex sect. Rhomboidales Kükenthal and is characterized by the involucral bracts surpassing the inflorescence; the trigonous, rhombic to ovoid perigynia with columniform bidentate apical beaks, and by the elliptic-rhomboid, trigonous nutlets that are constricted in the middle part. According to the above characteristics C. longipetiolata and C. diaoluoshanica are clearly different ( Fig.1;  Fig. 3, A-B and E-F).

Relationships
C. diaoluoshanica can be distinguishing from its related species by the following key.