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

Han, Meng-Qi, Liu, Yan & Zhang, Li-Bing, 2018, Eight new species of Polystichum (subg. Haplopolystichum; Dryopteridaceae) from limestone caves in Guangdong and Yunnan, China, with reference to species diversity in the karst terrains at high elevations in subtropical areas, Phytotaxa 365 (2), pp. 145-168 : 164-166

Polystichum superum Li Bing Zhang, M.Q.Han & Yan Liu , sp. nov. ( Figures 15 , 16 )

Type:— CHINA. Yunnan: Mengzi City, Mingjiu Town, Shidong Village, the Stone Cave , alt. 1880 m, 23°29 ′ 21 ″ N, 103°37 ′ 10 ″ E, in a limestone cave, 22 September 2016, Mengqi Han, Yang Dong & Tianfeng Lü HMQ1160 (holotype IBK! , isotype MO! ).

Diagnosis:— Polystichum superum is most similar to P. cavernicola Li Bing Zhang & H.He in He & Zhang (2011: 122) in having lamina slightly reduced toward lamina base, pinnae oblong and with rounded apex, but the former has a ratio of pinna length to width greater (ca. 2.2:1), pinnae slightly imbricate, basiscopic base of pinnae often forming a 60–80-degree angle with rachis, and perispores with cristate sculpturing, while the latter has a lesser ratio of pinna length to width (0.9–1.2:1), pinnae not imbricate, basiscopic base of pinnae often forming a 75–120-degree angle with rachis, and perispores with verrucate sculpturing.

Plants perennial, evergreen, 5.5–16 cm tall. Rhizomes ascending, ca. 1 cm long, 0.5–0.8 cm diam., with remnant bases of old petioles; roots dull brown when dried, up to 13 cm long, ca. 0.3 mm diam. Leaves in tufts, 5–12 per rhizome; petioles 1–4.5 cm long, 0.5–0.8 mm diam., basal portions covered with scales, scales ovate or ovate-lanceolate, 0.25– 1.8 × 0.2–0.65 mm, papery, dull brown, edges with irregular teeth, apex acuminate; distal petiole scales ovate or ovate-lanceolate, 0.47–0.73 × 0.15–0.26 mm, membranous, margins irregularly short-ciliate, apex caudate. Laminae ellipticoblanceolate, 1-pinnate, 3.5–11.5 × 1.3–2.2 cm, apex acute to acuminate; rachises 0.4–0.6 mm diam., scales subulate, lanceolate or ovate-lanceolate, light to dull brown, 0.6–2.2 mm long including tip, 0.25–0.75 mm wide at base, margins sparsely ciliate, apex caudate. Pinnae 12–21 pairs, oblong, middle ones 0.8–1.3 × 0.3–0.5 cm, basal 3–6 pairs slightly reduced toward lamina base, basalmost pairs ca. 2/3 as large as middle ones, basalmost two pairs 0.3–0.7 cm apart, middle pairs 0.4–0.5 cm apart, all pinnae papery, alternate, not overlapping rachis, basiscopic margins straight, entire, acroscopic margins repand, basiscopic margins forming a 60–80° angle with rachis, apex rounded, base cuneate and asymmetric, acroscopic sides much broader, pinna petiolues 0.25–0.45 mm long, auricles acute at apex, abaxially with microscales, microscales narrow-type, lanceolate, light brown, 0.36–0.8 mm long, ca. 0.07 mm wide at base; adaxially glabrous; veins visible abaxially but somewhat obscure adaxially, lateral veins free, single or forked. Lowest 2–5 pairs of pinnae sterile; sori terminal on lateral veins of fertile pinnae, 1–5 on acroscopic side of fertile pinnae, 0–1 on distal basiscopic side of fertile pinnae, ca. 1 mm diam., closer to pinna margins than to costa (centers of sori 0.7–1.5 mm from pinna margins, 1.5–3 mm from costa), centers 1.5–2.2 mm apart from one another; indusia rounded, light brown, 0.9–1.2 mm diam., margins erose. Spores rounded in polar view and elliptic in equatorial view; perispore sculpture cristate with shallow cristae and granules.

Geographical distribution:— Polystichum superum is only known from northeastern Yunnan, Southwest China. It is likely endemic to the Stone cave in Mengqi City.

Ecology:— Polystichum superum grows inside a limestone cave at an elevation of 1880 m with humid and shady conditions.

IUCN Red List category:—CR-Critically Endangered: Only one population with about 80 plants was seen in the field.

Etymology:—The species epithet is based on the Latin, superum, upper, referring to the sori often borne at the acroscopic side of each pinna.

Vernacular name:—ŀfflHẄ(shang guo er jue).

Notes:— Polystichum superum and P. deltatum (see above) were discovered from the same cave with the former growing at the entrance and the latter deeper inside.

Figures

FIGURE 15. Polystichum superum Li Bing Zhang, M.Q.Han & Yan Liu.—A. Habitat and plant.—B. Petioles.—C–E, G, H. Portions of abaxial lamina.—D, E. Portions of rachises with pinnae.—F, L. Polar and equatorial views of spores under SEM.—J. Sporangium before dehiscence.—K. Outside view of the cave where the new species was discovered.

FIGURE 16. Polystichum superum Li Bing Zhang, M.Q.Han & Yan Liu.—A. Habit of plants.—B. Portion of abaxial lamina.