Polystichum multispinulosum Li Bing Zhang, M.Q.Han & Yan Liu, 2016

Han, Meng-Qi, Liu, Yan & Zhang, Li-Bing, 2016, Seven new species of Polystichum (subg. Haplopolystichum; Dryopteridaceae) from southern China, Phytotaxa 280 (3), pp. 201-221 : 209-212

Polystichum multispinulosum Li Bing Zhang, M.Q.Han & Yan Liu , sp. nov. ( Figures 7 , 8 )

Type:— CHINA. Guizhou: Zhijin County, Houzhai Town , Chuandong Village , elev. 1980 m, 26°37 ′ 22 ″ N, 105°35 ′ 12 ″ E, inside a limestone cave, 25 May 2015, Mengqi Han & Jinquan Huang HMQ482 (holotype IBK!; isotypes CDBI!, MO!) .

Diagnosis:— Polystichum multispinulosum is most similar to P. lanceolatum ( Baker 1880: 494) Diels (1900: 193) in having long spinules on the pinna margin, but the former has pinnae of 0.4–0.5 cm wide and blackish brown rachis scales, while the latter has pinnae of 0.2–0.3 cm wide and brown rachis scales.

Plants perennial, evergreen, 20–23 cm tall. Rhizomes ascending, 1.4–1.8 cm long, ca. 1 cm diam., with remnant bases of old stipes; roots dull brown when dried, 3–8 cm long, ca. 0.3 mm diam. Leaves in tufts, 10–15 per rhizome; petioles 1.5–2.5 cm long, ca. 1 mm diam., basal portions densely covered with scales, scales ovate-lanceolate, 3–4.5 × 1–2 mm, papery, darkish brown, margins lighter in color and with short outgrowths to nearly entire, apex caudate; distal petiole scales similar but narrower and shorter, deltoid or ovate-lanceolate, 2–3.5 × 0.4–0.8 mm, membranous, margins irregularly erose or short-ciliate, apex caudate. Laminae oblanceolate, 1-pinnate, 15–20 × 2.3–2.7 cm, apex acuminate, green when dried; rachises 0.7–1 mm diam., scales deltoid, subulate or ovate-lanceolate, dull brown, 2–2.7 mm long including tip, 0.4–0.6 mm wide at base, margins sparsely ciliate, apex long-caudate. Pinnae 25–30 pairs, oblong, 0.7–1.3 × 0.4–0.5 cm, basalmost 4–6 pairs smaller toward lamina base, basalmost pair nearly half as large as middle ones, 0.6–0.7 cm apart, middle pairs 0.5–0.6 cm apart, all pinnae papery, alternate, basiscopic proximal margins entire, acroscopic margins and basiscopic distal margins toothed, teeth with spines of 0.6–0.8 mm long, basiscopic margins forming a 60–90° angle with rachis, apex acute, base cuneate and asymmetric with acroscopic sides being much broader, petioles ca. 0.6 mm long, abaxially sparsely with microscales, microscales subulate, light brown, 1–1.7 mm long, 0.4–0.6 mm wide at base, margins with irregular outgrowths; adaxially glabrous; veins visible abaxially but somewhat obscure adaxially, lateral veins free, single or forked. Lower 1–3 pairs of pinnae sterile; sori terminal on lateral veins of fertile pinnae, 1–6 on acroscopic side of fertile pinnae, 0–3 on distal basiscopic side of fertile pinnae, ca. 1.5 mm diam., approximately in middle of pinna margins and midrib (centers of sori 0.8–1.8 mm from pinna margins, 0.8–1.1 mm from midrib), centers 1.6–2 mm apart from one another; indusia rounded, ca. 0.4 mm diam., margins lacerate. Spores round in polar view and elliptic in equatorial view; perispore sculpture cristate and shallowly reticulate.

Geographical distribution:— Polystichum multispinulosum is only known from a single cave in northwestern Guizhou, Southwest China. It is likely endemic to that limestone cave.

Ecology:— Polystichum multispinulosum grows inside a limestone cave at an elevation of 1980 m with humid and shady conditions.

IUCN Red List category:—CR-Critically Endangered: Only one population with about 100 plants was seen in the field.

Etymology:—The species epithet is based on the Latin prefix, multi-, many, and the Latin adjective, spinulosum, spinulose, referring to the many spinules the species has on pinna margin.

Taxonomic notes:—Morphologically Polystichum multispinulosum has no close relatives in P. subg.

Haplopolystichum. It is superficially similar to P. lanceolatum in having long spinules on the pinna margin. It is also somehow similar to P. liui Ching in Ching & Liu (1983: 28) but it has longer spinules on the pinna margin. The blackish scales on the rachis distinguishes the new species from all other similar species too. In addition, the perispore sculpture is cristate with numerous shallow reticular formation, not known in any other species of the genus.

Figures

FIGURE 7. Polystichum multispinulosum.—A. Inside view of the cave where the new species was discovered.—B, C. Habitats and plants.—D. Portion of abaxial lamina.—E. Portion of adaxial lamina.—F. Lower portion of plant.—G. Portion of pinna showing sori.—H. Equatorial view of spore under SEM.—I. Polar view of spore under SEM.

FIGURE 8. Polystichum multispinulosum.—A. Habit.—B. Portions of abaxial and adaxial lamina.