Pilea nonggangensis Y. G. Wei, L. F. Fu & A. K. Monro, 2017

Pilea nonggangensis Y. G. Wei, L. F. Fu & A. K. Monro View in CoL , sp. nov. ( Figs. 2–3 View FIGURE 2 View FIGURE 3 )

Most similar to P. basicordata from which it differs by being dioecious, having peltate leaf blades, membranous stipules inflorescences paired in each axil and longer bracts.

Type:— CHINA. Guangxi: Longzhou County, Nonggang National Nature Reserve , 331 m, 22.477778°N, 106.939444°E ( WGS84 ), 7 March 2014, in flower, S.L. Huang HSL149 (holotype IBK! GoogleMaps , isotypes IBK! GoogleMaps ).

Shrubs or subshrubs, terrestrial. Rhizomatous and stoloniferous, stem 50–300 × 5 mm, drying light green or yellowgreen or flushed red when fresh, glabrous, cystoliths fusiform, the internodes compact, 1–3 mm. Stipules 10–40 × 5–15 mm, oblong, drying brown, thinly papery.Leaves petiolate, distichous; petioles 20–200 mm, glabrous, cystoliths densely scattered; laminae at each node equal or subequal, 40–180 × 20–120 mm, length:width ratio 1.5–2:1, oblong, elliptic or ovate, peltate, succulent, chartaceous to subcoriaceous when dry, cystoliths densely scattered on both surfaces, <0.1 mm, linear or fusiform, 3-veined, secondary nerves 8–12 pairs, borne at 80–90° to the midrib; upper surface drying grey-green, dark green when fresh, glabrous; lower surface drying light green, green when fresh, glabrous; base obtuse or subtruncate; margin entire for basal 1/2 then weakly serrate, apex subcaudate. Inflorescences apical, borne in pairs, unisexual, staminate and pistillate inflorescences synchronous but born on separate stems; bracts triangular-ovate, ca 3 mm; bracteoles triangular-ovate, ca 2 mm. Staminate inflorescences 40–170 mm, bearing 110–130 flowers in a loose cyme; peduncle 20–125 × 1 mm, glabrous, cystoliths densely scattered on basal section, sparsely upside; pedicels ca 0.8 mm, glabrous. Staminate flowers 1 × 1 mm, red, drying brown; tepals 4, ca 1.4 mm; valvate, fused for their basal 1/2, elliptic, glabrous, the subapical appendage ca 0.2 mm, corniculate, glabrous; stamens 4. Pistillate inflorescences 40–130 mm, bearing 200–300 flowers in a loose cyme; peduncle 20–90 × 1 mm, cystoliths densely scattered on basal section, glabrous; pedicels ca 0.5 mm. Pistillate flowers ca 1 mm, tepals 4, equal, glabrous, triangular-ovate, ca 0.4 mm in length. Infructescences 80–130 mm; peduncle 50–90 mm; achenes ca 1.5 × 1 mm, ovoid, symmetrically.

Distribution:— Known only from the type locality, the Nonggang National Nature Reserve, Longzhou County, Guangxi Province. Pilea nonggangensis was observed growing on wet limestone in forest shade on a limestone mount at an elevation of 331 m.

Etymology:— Pilea nonggangensis is named after the type locality, Nonggang National Nature Reserve.

Discussion:— Our analyses of DNA sequence data suggest that Pilea nonggangensis falls within Pilea sect. Tetrameris (BP = 84), a clade demonstrated to be monophyletic by Monro (2006) and characterised by both staminate and pistillate flowers having four tepals. Within sect. Tetrameris Pilea nonggangensis most closely resembles P. basicordata from which it can be distinguished based on sexual system, leaf blade, stipule, inflorescence and bract morphology as summarized in Table 2 View TABLE 2 .

Conservation status:— A Global Species Conservation Assessment was undertaken using the IUCN methodology (2001, 2016) using criteria D. Pilea nonggangensis is known from a single locality (IUCN criteria D2) where the population comprises ca 200 individuals (IUCN criteria D1). Using the IUCN methodology for P. nonggangensis would be Endangered (EN), however no plausible threat could be found to confirm its status as the population is located within a protected area not under threat in the near future, in addition, considering surrounding area has not been completely explored there may be hitherto undocumented additional populations. For these reasons we have revised the Global Species Conservation Assessment for P. nonggangensis to Vulnerable (VU).