Polystichum zhijinense Li Bing Zhang, Yi F.Duan & Kropf, 2017

Duan, Yi-Fan, Kropf, Matthias & Zhang, Li-Bing, 2017, Polystichum zhijinense (subg. Haplopolystichum; Dryopteridaceae), a new cave species of Polystichum from Guizhou, China, Phytotaxa 331 (1), pp. 124-130 : 124-127

Polystichum zhijinense Li Bing Zhang, Yi F.Duan & Kropf , sp. nov. (Figs. 1 & 2).

Diagnosis:— Polystichum zhijinense is similar to P. fengshanense Li Bing Zhang & H. He (2011: 859) in having pinnae oblong and entire or shallowly repand (not aristate-spinulose on the margin), but the former has pinna apex acute, microscales ovate-lanceolate to lanceolate, and sori closer to the pinna margins and located only at acroscopic side of pinnae (rarely lower pairs of pinnae with one sorus at the basiscopic side), while the latter has pinna apex rounded, microscales lanceolate to linear, and sori closer to the midrib and located at both acroscopic and basiscopic sides of pinnae.

Type:— CHINA. Guizhou: Zhijin County, Houzhai Xiang , Pianyan Cun , Shuanglongtan Zu , Suoyichong , 26°38’13’’N, 105°36’41’’E, elev. 1760 m, at a cave entrance, 9 August 2017, Li Bing Zhang, Yi-Fan Duan & Matthias Kropf 9517 (holotype CDBI!; isotypes CDBI!, MO!, NF!) .

Figure 1. Polystichum zhijinense Li Bing Zhang, Yi F.Duan & Kropf. —A. Inside view of the cave where the new species was discovered.— B. Habitat at the cave entrance.—C, D. Habit of the new fern in the cave.—E. Abaxial view of lamina (dried specimen).—F. Equatorial view of spore.

Figure 2. Polystichum zhijinense Li Bing Zhang, Yi F.Duan & Kropf. —A. Habit.—B. Adaxial view lamina.—C. Portion of abaxial lamina showing sorus distribution.—D. Lower portion of abaxial lamina showing microscales.

Plants perennial, evergreen, 4–15 cm tall. Rhizomes ascending or subascending, 0.5–1.5 cm long, 0.1–1.2 cm in diam.. Leaves fastigiate, 6–11 per rhizome, green or greyish green; stipes 0.5–2.5 cm long, 0.3–1.0 mm in diam., adaxially sulcate, basal portions densely covered with scales, scales ovate-lanceolate to lanceolate, 0.5–2.5 × 0.3–1.5 mm, chartaceous, darkish brown, margins irregularly ciliate, apex acuminate; distal stipe scales similar but narrower and shorter, 0.3–2 × 0.2–1.2 mm, margins slightly ciliate, long-acuminate. Laminae narrowly elliptic-lanceolate, 1–pinnate, 3–12 × 1.0– 2.5 cm, apices acute to acuminate, basalmost 2–6 pairs narrowed toward base, greyish green when dried; rachises 0.2–0.9 mm in diam., adaxially sulcate, scales long lanceolate to ovate-lanceolate, brown, 0.2–1.8 mm long, 0.2–1 mm wide at base, margins sparsely toothed, apices long-caudate. Pinnae 8–22 pairs, alternate, oblong, 0.3–1.2 × 0.1–0.6 cm, basalmost 1–4 pairs slightly smaller toward lamina base, 0.2–0.8 cm apart; pinna bases obviously asymmetrical; all pinnae herbaceous, margins shallowly repand and with very short spinules, apices acute, bases cuneate, but asymmetric from midribs with acroscopic sides being much broader, short-petiolate (petioles 0.2–0.5 mm long), abaxially sparsely with ovate-lanceolate to lanceolate and light brown microscales, ca. 0.2–0.5 mm long, 0.1– 0.3 mm wide at base; adaxially glabrous; venation visible abaxially and slightly obscure adaxially, lateral veins free. Upper portions of all pinnae fertile, lower portions mostly fertile and sometimes lower 1–6 pairs of pinnae sterile; sori terminal on shorter veinlets, 1 row on acroscopic side of midrib of pinna, close to margins, (1–)2–4(–5) on acroscopic side of fertile pinnae, usually none or only one on distal basiscopic side of fertile pinnae, 0.8–2.0 mm in diam., closer to pinna margins than to midrib (centers of sori 0.5–2 mm from pinna margins, 0.8–3 mm from midrib), centers ca. 0.8–3 mm apart from one another; indusia present, peltate, light brown, erose on margins. Perispore sculpturing cristate with spinules.

Geographical distribution:— Polystichum zhijinense is only known from one locality in northwestern Guizhou, China. Our extensive fieldwork in Guizhou in and before 2017 did not find additional occurrences of the species.

Habitat:— Polystichum zhijinense was observed to grow inside a large-sized karst cave at an elevation of 1760 m with humid and shady conditions. The cave entrance is about 30 × 40 m in size.

IUCN Red List category:—Only one population is known from the type locality and comprised about 40 plants. The status of the new species clearly should be CR-Critically Endangered category based on current information available and following IUCN (the International Union for Conservation of Nature and Natural Resources) guidelines ( IUCN 2015).

Etymology:—Based on the Chinese pinyin, zhijin, the name of the county in northwestern Guizhou, China, and the Latin suffix, -ense, of origin, referring to the type locality of the species.