Polystichum menglaense Z.L.Liang & Li Bing Zhang, 2021

Liang, Zhen-Long, He, Zhao-Rong & Zhang, Li-Bing, 2021, Polystichum dongchuanense and P. menglaense (subg. Haplopolystichum; Dryopteridaceae), two new ferns from Yunnan, China, Phytotaxa 479 (1), pp. 114-120 : 117-119

Polystichum menglaense Z.L.Liang & Li Bing Zhang , sp. nov. ( Fig. 3 ).

Type:— CHINA. Yunnan: Mengla County, Mengyuan Town , elev. 700 m, 21°42’43.50”N, 101°22’50.87”E, on rocks in shade, 8 August 2018, Z.- L . Liang, D. Wang LZL1294 (holotype PYU!; isotype PYU!) .

Diagnosis:— Polystichum menglaense is most similar to P. deltodon ( Baker 1880: 494) Diels (1899: 191) in plant size, but the former has oblong-lanceolate pinnae with a rounded apex, and sori are terminal at the upper part, whereas the latter has deltoid-lanceolate pinnae with an acuminate apex, and sori are distributed on whole fertile pinnae

Plants perennial, evergreen, (20–) 25–28 cm tall. Rhizomes erect, ca. 2 cm long, ca. 1.2 cm in diam.; roots dark when dried, up to 10 cm long, ca. 0.3 mm in diam. Leaves in tufts; petioles 5–7 cm long, ca. 0.8-1 mm in diam, stramineous basal portions covered with scales; proximal petiole scales ovate, 1–2 × 0.7–1.2 mm, membranous to papery, brown, margins irregular, apex acuminate, cells rectangular in the middle, twisted in the margins; distal petiole scales ovate-lanceolate, 0.8–1.2 × 0.4–0.8 mm, membranous, margins fimbriate, apex long-acuminate or caudate. Laminae lanceolate, abaxially green, adaxially light green; 1-pinnate, 18–20 cm long, 3–3.5 cm wide, apex acuminate; rachises ca. 0.7 mm in diam., stramineous brown, adaxially sulcate; rachis scales narrow lanceolate, light brown, up to 0.8 mm long including tip, 0.3 mm wide at base, margins fimbriate, apex long-caudate. Pinnae in 26 pairs, alternate, separate from each other, 1–3 mm distance, oblong lanceolate, basal cuneiform, margins sinus, apex acuminate, papery, maximal pinnae 2.1–2.4 × 0.4–0.6 cm, basal pinnae narrowing toward lamina base and basal 1 pair reflexed, largest pinnae located at middle part of lamina, proximal margins slightly overlapping rachis, upward, forming a 70° angle with rachis; pinna petioles invisible; adaxially glabrous; abaxially with microscales; microscales narrowly lanceolate, whitish brown, margins entire; costa sunken abaxially and protruding adaxially, veins obscure and invisible on adaxial side, bulgy and thickened on abaxial side, lateral veins free, forked. All but basal 5–8 pairs of pinnae fertile; sori terminal on lateral veins, ca. 1 mm in diam., in the middle between pinna margins and midribs or slightly closer to pinna margins, 1–3 on acroscopic side and 0–1 on distal basiscopic side, centers 2–3 mm apart from one another. Indusia peltate, orbicular, margins erose. Perispore ornamentation unknown.

Geographical distribution:— Polystichum menglaense is only found in Mengla County, Yunnan Province , and may represent an endemic species to southern Yunnan.

Ecology:— Polystichum menglaense was observed to grow on limestone rocks under tropical rain forest, at an elevation of about 700 m.

IUCN Red List category:—Only one population of Polystichum menglaense was found in Mengla. Based on current information and following the IUCN (The International Union for Conservation of Nature and Natural Resources) guidelines ( IUCN, 2017), this new species should be classified as Critically Endangered (CR).

Etymology:—The species epithet is based on the Chinese pinyin, mengla, the county name in southern Yunnan, and the Latin suffix -ense, of origin, referring to the type locality and the current known distribution of the species in Mengla County, Yunnan. The Chinese name is suggested as ‘©腊耳蕨 (meng la er jue)’.

Notes:—In Mengla, the southernmost part of Yunnan, there are only three species belonging to Polystichum sect. Haplopolystichum : P. acutidens , P. paradeltodon L.L. Xiang (1994: 265) , and the new species being described here. Polystichum menglaense is distinguishable from P. acutidens by having rounded pinna apices (vs. acute pinna apices) and different from P. paradeltodon by having oblong-lanceolate pinnae (vs. oblong pinnae) and partially fertile frond (vs. fully fertile frond). Both Polystichum menglaense and P. paradeltodon are calciphiles and very rare in Mengla, Yunnan, whereas P. acutidens grows in both acidic and basic soils and is more common.

Figures

FIGURE 3. Polystichum menglaense.—A. Habitat.—B. Portion of abaxial lamina from a dry specimen.—C. Habit of the plant on the rock in the shade.—D. Basal petiole scale.—E. Microscale from abaxial lamina surface.—F. Rachis scale.—G. Portion of abaxial lamina from a freshly collected specimen.