Polystichum duyunense Li Bing Zhang, Xin Y.Miao & Chun X.Li, 2017

Polystichum duyunense Li Bing Zhang, Xin Y.Miao & Chun X.Li View in CoL , sp. nov. ( Figs. 1 View FIGURE 1 & 2 View FIGURE 2 )

Type:— CHINA. Guizhou Province: Duyun city, 26°2’36’’N, 107°26’60”E, in a limestone cave, elev. Ca. 840 m, 9 June 2016, Li-Bing Zhang, Yi-Fan Duan, Ngan Thi Lu & Xin-Yuan Miao 9217 (holotype CDBI! GoogleMaps ; isotypes CDBI! GoogleMaps , MO! GoogleMaps , herb. Pei-Shan Wang! GoogleMaps ).

Diagnosis:— Polystichum duyunense is somewhat similar to P. cavernicola Li Bing Zhang & H. He (2011: 122) in having oblong pinnae, but the former has pinnae larger, often angled basiscopically, and somewhat imbricate, while the latter has pinnae smaller, angled acroscopically, and apart from each other.

Plants perennial, evergreen, 27–47 cm tall. Rhizomes ascending, with remnant bases of old petioles; roots unseen (left undisturbed). Leaves fastigiate, 9–14 per rhizome; petioles 9–17 cm long, 1–1.2 mm diam., basal portions densely covered with scales, scales broad-lanceolate to ovate-lanceolate, 4.4–6.3 × 1.0– 2.8 mm, papery, blackish brown, edges with lighter color and entire with a few sparsely erose outgrowths several-cell wide at the base, apex acuminate; distal petiole scales similar but narrower and shorter, brown, lanceolate to ovate-lanceolate, 2.1–4.2(–6.0) × 0.9–1.5 mm, membranous, edges long-ciliate, apex long caudate. Laminae lanceolate, 1-pinnate, 17.7–29.5 × 3.8–5.5 cm, apex acuminate, yellowish green when dried; rachises 0.4–1.3 mm in diam., adaxially sulcate, scales of rachis similar to distal petiole scales but smaller, lanceolate to ovate-lanceolate, 1.5–2.4 mm long including tip, 0.4–1.3 mm wide at base, light brown, margins regularly ciliate, apex long caudate. Pinnae 17–26 pairs, dimidiate to oblong, 1.7–2.8 × 0.7–1.2 cm; basalmost 0–1 pair slightly smaller (smaller laminae) or slightly larger (larger laminae), 1.7–2.5(–2.7) cm apart, middle pairs 0.9–1.5 cm apart, all pinnae papery, mostly alternate, some basal pinnae opposite or subopposite, basiscopic proximal margins entire, acroscopic margins and basiscopic distal margins serrulate, auricles mucronate, 0–2.5 × 0–5.0 mm, apex acuminate, base cuneate and asymmetric from midribs with acroscopic sides being much broader, basiscopic margins forming about 60–85° angles with rachis, petioles ca. 0.65 mm long, abaxially sparsely with lanceolate to subulate microscales, light brown, 0.75–1.0 mm long, ca. 0.25 mm wide at base, apex caudate; adaxially glabrous; venation visible adaxially and abaxially, obviously raised abaxially, distinct adaxially, lateral veins free and forked. Lamina completely fertile (occasionally basal pairs of pinnae sterile); sori terminal on lateral veins of fertile pinnae, 1–9 on acroscopic side of fertile pinnae, 0–3 on distal basiscopic side of fertile pinnae, ca. 1 mm in diam., closer to pinna margins than to midrib (centers of sori 0.75–2.25 mm from pinna margins, 0.75–5.8 mm from midrib), centers 1.8–2.5 mm apart from one another; indusia peltate, margins shallow toothed, 0.4–0.9 mm in diam., membranous, light brown, deciduous.

Geographical distribution:— Polystichum duyunense is only known from the type locality in Duyun County, Guizhou Province, Southwest China.

Ecology:— Polystichum duyunense was observed to grow in a wet limestone cave at an elevation of ca. 840 m.

IUCN Red List category:—Only one population with about 20 plants are known from the type locality. The status of the new species clearly should be classified as CR- Critically Endangered category based on current information and following IUCN (the International Union for Conservation of Nature and Natural Resources) guidelines ( IUCN 2015).

Etymology:—The species epithet is from Duyun, the Chinese pinyin name of the city in southern Guizhou, where the new species was discovered.

Additional specimens examined (paratypes):— CHINA. Guizhou Province: Duyun city, Mochong Zhen, Shitou Zai , close to a concrete factory, 26°2’36’’N, 107°26’60”E, in a limestone cave, elev. ca. 840 m, 9 June 2016, Meng-Qi Han HMQ1051 ( CDBI!, IBK!) GoogleMaps .