Polystichum paucicarpum 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 : 214-217

Polystichum paucicarpum Li Bing Zhang, M.Q.Han & Yan Liu , sp. nov. ( Figures 11 , 12 )

Type:— CHINA. Guizhou: Tongzi County, Shixi Town, Tangli Village, elev. 1170 m, 28°47 ′ 17 ″ N, 107°11 ′ 19 ″ E, 26 Jul. 2015, Mengqi Han & Shuwan Li HMQ705 (holotype IBK!, isotype CDBI!).

Diagnosis:— Polystichum paucicarpum is most similar to P. yuanum Ching (1958 : t. 235) in having slightly toothed pinna margins, but the former has lamina shorter than 13 cm, pinnae fewer than 25 pairs per lamina, most pinnae not reflexed, and lower pinnae sterile, while the latter has lamina up to 30 cm long, pinnae up to 30 pairs per lamina, most pinnae reflexed, and all pinnae fertile.

Plants perennial, evergreen, 10–15 cm tall. Rhizomes ascending, 1–1.5 cm long, ca. 1 cm diam., with remnant bases of old stipes; roots dull brown when dried, 4–8 cm long, ca. 0.5 mm diam. Leaves in tufts, 9–15 per rhizome; petioles 2–3 cm long, 0.8–1 mm diam., basal portions densely covered with scales, scales ovate to lanceolate, 1.5–2 × 1–1.5 mm, chartaceous, dull brown, margins with light color and toothed, apex caudate; distal petiole scales similar but narrower and shorter, 0.7–1.5(–2) × 0.3–0.8 mm, membranous, margins irregularly erose or short-ciliate, apex long-acuminate or caudate. Laminae oblanceolate, 1-pinnate, 8–13 × 0.8–1.8 cm, apex acuminate, dark green when dried; rachises 0.5–0.7 mm diam., scales ovate-lanceolate to lanceolate, dull brown, 1.1–1.8 mm long including tip, 0.5–0.7 mm wide at base, margins sparsely ciliate, apex long-caudate. Pinnae 16–25 pairs, oblong, 0.3–1 × 0.2–0.5 cm, basalmost 4–7 pairs gradually smaller toward lamina base, basalmost pair nearly 1/4 as large as middle ones, 0.4–0.6 cm apart, middle pairs 0.5–0.7 cm apart, all pinnae papery, alternate, basiscopic margins entire, acroscopic margins shallowly toothed and acute, teeth with 3–4(–5) spines of 0.4–0.7 mm long, basiscopic margins forming a nearly right angle with rachis, apex rounded, base cuneate and asymmetric with acroscopic sides being much broader, petioles 0.2–0.3 mm long, abaxially with microscales, microscales lanceolate to ovate-lanceolate, brown, ca. 1mm long, 0.3 mm wide at base; adaxially glabrous; veins visible abaxially but somewhat obscure adaxially, lateral veins free, single or forked. Lower 8–11 pairs of pinnae sterile; sori terminal on lateral veins of fertile pinnae, (1–)2–3(–4) on acroscopic side of fertile pinnae, absent on distal basiscopic side of fertile pinnae, ca. 1 mm diam., closer to pinna margins than to midrib (centers of sori 0.4–1.3 mm from pinna margins, 1–2.5 mm from midrib), centers 0.5–2 mm apart from one another; indusia rounded, nearly entire. Spores round in polar view and elliptic in equatorial view; perispore sculpture cristate and granulate.

Geographical distribution:— Polystichum paucicarpum is only known from northeastern Guizhou, Southwest China. It is likely that it is endemic to that limestone cave.

Ecology:— Polystichum paucicarpum grows inside a limestone cave at an elevation of 1170 m with humid and shady conditions.

IUCN Red List category:—CR-Critically Endangered: Only one population with about 200 plants was seen in the field.

Etymology:—The species epithet is based on the Latin prefix, pauci-, few, and the Latin noun, - carpum, fruit, referring to the few sori on fertile pinnae of the new species.

Taxonomic notes:— Polystichum paucicarpum is somewhat similar to P. cavernicola Li Bing Zhang & H. He (2011: 122) in having oblong pinnae, but the former has the majority of the pinnae sterile, pinna margins with sharp tips, and basiscopic pinna margins forming a nearly right angle with rachis, while the latter has the majority of the pinnae fertile, pinna margins with out sharp tips, and basiscopic pinna margins forming a 75–120° angle with rachis.

Figures

FIGURE 11. Polystichum paucicarpum.—A. Limestone mountains where the new species was discovered.—B, C. Habitats and plants.— D. Portions of adaxial laminae.—E. Portion of stipe showing scales.—F, G. Polar views of spores under SEM.

FIGURE 12. Polystichum paucicarpum.—A. Habit of plants.—B. Portion of abaxial lamina.