Polystichum hanmengqii Li Bing Zhang & Yan Liu, 2018

Polystichum hanmengqii Li Bing Zhang & Yan Liu View in CoL , sp. nov. ( Figures 5 View FIGURE 5 , 6 View FIGURE 6 )

Type:— CHINA. Guangdong: Lianzhou City, Lianzhou Subterranean River Scenic Area, Chukoudong , alt. 200 m, 25°00 ′ 25 ″ N, 112°19 ′ 09 ″ E, in a limestone cave, 17 July 2017, Mengqi Han & Lin Huang HMQ1434A (holotype IBK!) GoogleMaps .

Diagnosis:— Polystichum hanmengqii is most similar to P. hainanicola Li Bing Zhang, Liang Zhang & X.F.Gao (2013: 10) in having ratio of length to width of pinnae 2.5–3:1, pinnae repand on margin and rounded at apex, and sori close to the pinna margins, but the former has lamina fertile on the upper part only, proximal basiscopic margins of pinnae straight, and sori above costa of middle pinnae fewer than 4 and borne at both distal and proximal parts of pinnae, while the latter has whole lamina fertile, proximal basiscopic margins of pinnae curved, and sori above costa of middle pinnae up to 7 and borne at distal parts of pinnae only.

Plants perennial, evergreen, 34–38 cm tall. Rhizomes not seen. Leaves in tufts; petioles 11–13 cm long, ca. 1 mm diam., basal portions covered with scales, scales broad-lanceolate, ovate-lanceolate to ovate, 0.4–3 × 0.2–0.6 mm, papery, dark brown, edges with irregular teeth, apex acuminate or caudate; distal petiole scales often subulate, up to 2.2 × 0.4 mm, membranous, light brown, margins short-ciliate, apex caudate. Laminae lanceolate, 1-pinnate, 23–27 × 3–3.7 cm, apex acuminate; rachises ca. 1 mm diam., scales linear, subulate, rarely lanceolate, light brown, 1–2.5 mm long including tip, 0.18–0.36 mm wide at base, margins sparsely ciliate, apex long-caudate. Pinnae 21–24 pairs, oblong, 1.2–1.9 × 0.5–0.7 cm, lowest 7–9 pairs slightly reduced toward lamina base, basalmost pairs 1.2–1.5 × 0.6–0.8 cm, 1.4–1.6 cm apart, middle pairs 0.9–1.1 cm apart, all pinnae papery, alternate, slightly overlapping rachis or not, basiscopic margins slightly curved, entire, acroscopic margins shallowly crenulate, basiscopic margins forming a (80–)90–130° angle with rachis, apex acute, base cuneate and asymmetric, acroscopic sides much broader, pinna petiolues ca. 0.4 mm long, auricles rounded at apex, adaxially and abaxially sparsely with microscales, microscales narrow-type, linear, light brown, 0.2–0.45 mm long; veins visible abaxially but somewhat obscure adaxially, lateral veins free, single or forked. Lowest 9–12 pairs of pinnae sterile; sori terminal on lateral veins of fertile pinnae, 1–9 on acroscopic side of fertile pinnae, 0–4 on distal basiscopic side of fertile pinnae, 1–1.3 mm diam., closer to pinna margins than to costa (centers of sori 0.5–1.1 mm from pinna margins, 1–4.5 mm from costa), centers 2–3 mm apart from one another; indusia rounded, blackish in center, light brown outside, ca. 1 mm diam., margins erose.

Geographical distribution:— Polystichum hanmengqii is only known from northwestern Guangdong, South China. It is likely endemic to the cave in Lianzhou City.

Ecology:— Polystichum hanmengqii grows inside a limestone cave at an elevation of 200 m with humid and shady conditions.

IUCN Red List category:—CR-Critically Endangered: Only one population with about 50 plants was seen in the field.

Etymology:—The species epithet is in honor of one of the collectors of the type of the species, Han Mengqi.

Vernacular name:—ĀdzHẄ(meng qi er jue).

Notes:— Polystichum hanmengqii is one of the four species known so far with a ratio of length to width of pinnae greater than 2.5:1, and pinna margins repand (without spinules) or nearly entire. Other three species include P. guangxiense W.M.Chu & H.G.Zhou in Zhou et al. (1996: 205), P. hainanicola , and P. peishanii Li Bing Zhang & H.He (2009: 102) . Polystichum hanmengqii can be distinguished from P. guangxiense by having a ratio of length to width of pinnae 2.5–2.7:1 (vs. ca. 3: 1 in P. guangxiense ), lamina fertile at upper part only (vs. nearly all pinnae in P. guangxiense ), and pinna margins repand (vs. nearly entire in P. guangxiense ). Polystichum hanmengqii is distinguishable from P. peishanii by having rounded pinna apices (vs. acuminate or acute pinna apices in the latter; Zhang & Barrington 2013).

Polystichum hanmengqii is the second cave fern of Polystichum described from Guangdong Province, China; the first was P. hastipinnum G.D.Tang & Li Bing Zhang in Tang et al. (2017: 66).