Polystichum gejiuense Li Bing Zhang, M.Q.Han & Yan Liu, 2018

Polystichum gejiuense Li Bing Zhang, M.Q.Han & Yan Liu View in CoL , sp. nov. ( Figures 3 View FIGURE 3 , 4 View FIGURE 4 )

Type:— CHINA. Yunnan: Gejiu City, Kafang Town , inside a limestone cave facing north, elev. 1950 m, 25 March 2017, Mengqi Han HMQ1301 (holotype IBK! , isotypes CDBI! , MO! ).

Diagnosis:— Polystichum gejiuense is most similar to P. fengshanense Li Bing Zhang & H.He (2011: 859) in having pinnae oblong, entire, and pinna apex rounded, but the former has pinnae up to 15 pairs, indistinct auricles, a ratio of length to width of pinnae ca. 2:1, and sori close to pinna margins, while the latter has pinnae up to 24 pairs, distinct auricles, a ratio of length to width of pinnae ca. 1.5:1, and sori closer to the costa.

Plants perennial, evergreen, 11–15 cm tall. Rhizomes ascending, ca. 0.7 cm long, ca. 0.6 cm diam., with remnant bases of old petioles; roots dull brown when dried, up to 11 cm long, ca. 0.3 mm diam. Leaves in tufts; petioles (1–) 3–7.5 cm long, ca. 0.5 mm diam., basal portions covered with scales, proximal scales ovate to ovate-lanceolate, 0.9–2.5 × 0.2–0.6 mm, papery, dark brown, acuminate, edges nearly entire; distal petiole scales sparse, lanceolate or subulate, up to 1.4 × 0.4 mm, membranous, margins with irregular teeth, apex caudate. Laminae elliptic-lanceolate, 1-pinnate, 5.5–8 × 1.7–2.2 cm, apex acuminate, green when dried; rachises ca. 0.5 mm diam., scales subulate, lanceolate to ovate-lanceolate, light brown, 0.25–1.7 mm long including tip, 0.07–0.36 mm wide at base, margins sparsely with teeth, apex long-caudate. Pinnae 13–17 pairs, oblong, 0.8–1 × 0.3–0.45 cm, basalmost 2–3 pairs slightly reduced toward lamina base, basalmost pairs ca. 3/4 as large as middle ones, basalmost two pairs 0.4–0.7 cm apart, middle pairs 0.3–0.45 cm apart, all pinnae papery, alternate, slightly overlapping rachis or not, basiscopic margins slightly curved, entire, acroscopic margins with small teeth or nearly entire, basiscopic margins forming a (70–)80–90(–110)° angle with rachis, apex rounded, base cuneate and asymmetric, acroscopic sides much broader, pinna petiolues ca. 0.2 mm long, auricles rounded at apex, abaxially with microscales, microscales narrow-type, lanceolate, whitish brown, 0.2–0.7 mm long, 0.09–0.15 mm wide at base, margins entire; adaxially glabrous; veins visible abaxially but somewhat obscure adaxially, lateral veins free, single or forked. All pinnae fertile or lowest 1–3 pairs sometimes sterile; sori terminal on lateral veins of fertile pinnae, 5–8 on acroscopic side of fertile pinnae, 0–2 on distal basiscopic side of fertile pinnae, ca. 1 mm diam., closer to pinna margins than to costa (centers of sori 0.5–0.9 mm from pinna margins, 0.7–3.2 mm from costa), centers 1–1.3 mm apart from one another; indusia peltate, light brown, ca. 1 mm diam., margins nearly entire. Spores rounded or slightly deltoid in polar view and elliptic in equatorial view; perispore sculpture cristate with numerous spinules and granules.

Geographical distribution:— Polystichum gejiuense is only known from a single cave in southeastern Yunnan, Southwest China. It is likely endemic to the cave in Gejiu City.

Ecology:— Polystichum gejiuense grows inside a limestone cave at an elevation of 1950 m with humid and shady conditions.

IUCN Red List category:—CR-Critically Endangered: Only one population with about 30 plants was seen in the field. The natural vegetation on the mountain was mostly replaced by plantation of Cryptomeria japonica (Thunberg ex Linnaeus f. 1782: 421) D. Don (1839: 167) . Similar habitats to that of the new species were not seen in the nearby areas.

Etymology:—The species epithet is based on the Chinese pinyin, gejiu, the county name in southeastern Yunnan, and the Latin suffix- ense, of origin, referring to the type locality and the current known distribution of the species in Gejiu County, Yunnan.

Vernacular name:—ṪDzHẄ(ge jiu er jue).

Notes:—In addition to the differences between Polystichum gejiuense and P. fengshanense listed above, the new species has relatively longer petioles, the ratio of length of lamina to length of petiole is up to 0.7:1, and only 1–2 pairs of basal pinnae are shortened toward the lamina base. In contrast, P. fengshanense has relatively shorter petioles, the ratio of length of lamina to length of petiole is up to 5:1, and up to 9 pairs of basal pinnae are shortened toward the lamina base.