Polystichum luteoviride Li Bing Zhang, Yi F. Duan, N.T.Lu & Liang Zhang, 2017

Polystichum luteoviride Li Bing Zhang, Yi F. Duan, N.T.Lu & Liang Zhang View in CoL , sp. nov. ( Figure 1 View FIGURE 1 ).

Diagnosis:— Polystichum luteoviride is similar to P. deflexum Ching ex W.M.Chu (1992: 47) in having crenate pinna margins, but the former has laminae yellowish green and pinnae oblong, strongly reflexed, and acute to obtuse at apex, while the latter has laminae green and pinnae lanceolate, slightly reflexed or even angled acroscopically, and acuminate at apex.

Type:— CHINA. Guizhou Province: Ziyun County, Bandang Zhen, Cuihe Village, in the Chaotian (Sky-Facing) Cave ( Fig. 1 View FIGURE 1 : A), 25°54’40’’N, 106°12’59”E, elev. 1200 m, 14 Jun. 2016, Li Bing Zhang, Yi-Fan Duan, Ngan Thi Lu & Xin-Yuan Miao 9296 (holotype CDBI! GoogleMaps ; isotypes CDBI! GoogleMaps , MO! GoogleMaps , NF! GoogleMaps , herb. Pei-Shan Wang! GoogleMaps ).

Plants perennial, evergreen, 4–35 cm tall. Rhizomes ascending or subascending, 1.0– 2 cm long, 0.7–1.5 cm in diam., with remnant bases of old stipes; roots dark brown when dried, 2–10 cm long, ca. 0.5 mm in diam. Leaves fastigiate, 6–15 per rhizome, yellowish green; stipes 5–7.5 cm long, 0.4–1.0 mm in diam., adaxially sulcate, basal portions densely covered with scales, scales ovate-lanceolate to lanceolate, 1.5–3.5 × 1.0– 2.5 mm, chartaceous, darkish brown, margins irregularly ciliate, apex acuminate; distal stipe scales similar but narrower and shorter, 1.0–2.5 × 0.5–1 mm, margins slightly ciliate, long-acuminate. Laminae narrowly elliptic-lanceolate, 1–pinnate, 3–27 × 1.0– 4.5 cm, apices acute to acuminate, basalmost 2–4 pairs narrowed toward base, yellowish green or green when dried; rachises 0.3–0.9 mm in diam., adaxially sulcate, scales long lanceolate to ovate-lanceolate and linear, brown, 0.8–2.5 mm long, 0.2–1.0 mm wide at base, margins sparsely toothed, apices long-caudate. Pinnae 11–25 pairs, alternate, trapezoid, 0.5–2.5 × 0.2–1.0 cm, basalmost 1–4 pairs slightly smaller toward lamina base, 0.5–1.2 cm apart; pinna bases obviously asymmetrical, with auricles deltoid and sharp pointing ascendant, apex of auricles acute, sometimes acroscopic bases with 1 free pinnule; basiscopic pinna margins forming an angle of (20–)30–60(–70)° with rachis; all pinnae papery, margins crenate and without spinules, apices acute to obtuse, base cuneate, but asymmetric from midribs with acroscopic sides being much broader, short-petiolate (petioles 0.3–1.0 mm long), abaxially sparsely with ovate-lanceolate to lanceolate and light brown microscales, ca. 0.2–0.6 mm long, 0.1–0.4 mm wide at base; adaxially glabrous; abaxially with visible venation and somewhat obscure adaxially, lateral veins free, single or forked. Distal parts of almost all pairs of pinnae fertile, proximal parts sterile; sori usually terminal on shorter veinlets, 1 row on each side of midrib of pinna, close to margins, (1–)3–8(–11) on acroscopic side of fertile pinnae, 1–4(–5) on distal basiscopic side of fertile pinnae, 0.8–1.4 mm in diam., closer to pinna margins than to midrib (centers of sori 0.5–2.5 mm from pinna margins, 0.8–8 mm from midrib), centers ca. 0.8–2.5 mm apart from one another; indusia present, peltate, light brown, erose on margins.

Geographical distribution:— Polystichum luteoviride is only known from inside the Chaotian Cave, Cuihe Village, Bandang Zhen, Ziyun County, Guizhou Province. Our extensive fieldwork in Guizhou in 2016 did not find any additional occurrence of the species.

Ecology:— Polystichum luteoviride was observed to grow inside a large-sized kart cave at an elevation of 1200 m with humid and shady conditions. The cave is about 50 × 100 m in size.

IUCN Red List category:—The only population is known from the type locality and comprised about 200 plants. A mine ( Fig. 1 View FIGURE 1 : I) for construction material, located ca. 50 m away from the cave, seriously threatens the survival of the new species. The status of the new species clearly should be CE-Critically Endangered category based on current information and following IUCN (the International Union for Conservation of Nature and Natural Resources) guidelines ( IUCN 2015).

Etymology:—From the Latin prefix luteo-, yellow, and the Latin viride, green, referring the yellowish green leaves of the new species.