Asplenium cyrtosorum K.W.Xu, Li Bing Zhang & W.B.Liao, 2018

Xu, Ke-Wang, Jiang, Lei, Zhang, Li-Bing & Liao, Wen-Bo, 2018, Asplenium cyrtosorum (Aspleniaceae), a new fern from Yunnan, China, Phytotaxa 351 (2), pp. 176-180 : 176-179

Asplenium cyrtosorum K.W.Xu, Li Bing Zhang & W.B.Liao , sp. nov. ( Figs. 1 , 2 ).

Diagnosis:— The new species is most similar to Asplenium trapezoideum Ching (1931: 209) in having laminae deltate and often with a gemma below the terminal pinna, but the former has rhizomes erect, rhizome scales up to 4.5 mm long, laminae once imparipinnate, pinnae (2–)4–7(–9) pairs, rachises without narrow wings below apex, and veins 1- or 2-forked, while the latter has rhizomes short-creeping, rhizome scales up to 3 mm long, laminae 1-pinnate, pinnae 12–20 pairs, rachises with narrow wings below apex, and veins 2- or 3-forked, greyish.

Type:— CHINA. Yunnan: Pu’er City, Pu’er Sun River National Forest Park, elev. ca. 1200 m, 22°34’51.74”N, E 101°6’31.57”E, in wet soil or on wet rocks in tropical seasonal rainforest, 20 April 2017, Ke-Wang Xu & Lei Jiang XKW318 (holotype SYS!; isotypes MO!, SYS!) .

Plants (20–) 30–40 cm tall. Rhizomes erect, short, densely scaly, scales narrowly triangular, dark brown to black, ca. 1 × 4.5 mm, margins entire. Fronds caespitose; stipe robust, semiterete, (5–)12–20(–25) cm, adaxially green and sulcate, abaxially dull greyish brown, the grey colour often extending to rachis, with brown and narrowly triangular scales. Laminae deltate, 20–30(–40) × (5–) 6–10 cm, 1-imparipinnate; pinnae (2–)4–7(–9) pairs, subopposite at base, alternate above, shortly stalked, (1–)2–3(–5) mm, lower pinnae hardly reduced, ovate-lanceolate, (3–)4–6(–7) cm, base nearly symmetrical, cuneate, acroscopic side round, basiscopic side narrowly cuneate, margins serrate, apex acute, terminal pinnae similar to lateral ones but usually wider and more rhombic, 1–4 × 3–7 cm. Costae abaxially flat to slightly raised, adaxially with a longitudinal furrow (grooved), veins slender, ca. 0.15 mm in diameter, 1- or 2-forked. Fronds firmly herbaceous, papery or subcoriaceous, yellowish green at abaxial side, dark green at adaxial side, glaucous to yellowish green or greyish green when dry, abaxially with minute, brown, hair-like scales; rachises semiterete, greyish-green to stramineous abaxially, sparsely scaly, often gemmiferous below terminal pinnae. Sori narrow, slightly curved, (0.8–) 1–2 cm, usually on acroscopic veins, at an angle of 10°–25° with costa; indusia yellowish green when young, greyish brown when old, linear, membranous, margins entire, usually opening toward costa, persistent.

Geographical distribution:— Asplenium cyrtosorum is currently known only from the type locality in Pu’er Sun River National Forest Park, Pu’er City, southwestern Yunnan, China. We found only a small population and did not find additional occurrences of the species nearby or anywhere else.

Habitat:— Asplenium cyrtosorum was observed to grow in humid and shady conditions on a cliff by a cement road at Pu’er Sun River National Forest Park in the tropical seasonal rainforest.

IUCN Red List category:— During our expedition, we found one population only distributed in a 10,000 m 2 area. The population included 40–50 individuals. This species is easily affected by natural hazard or anthropogenic activities, such as road construction. The narrow distribution in the single locality and the small population size of the new species justify its current status of CR-Critically Endangered, following IUCN guidelines ( IUCN 2015).

Etymology:— Based on the Greek prefix, cyrto- [kyrtos], curved, and the Greek suffix, -sorum, of sorus, referring to the slightly curved sori of the new species.

Vernacular name:—ẈPṩffdz (wân-guǒ tiě- jiǎo-jué).

Additional specimens examined:— CHINA. Yunnan: Pu’er City, Pu’er Sun River National Park, elev. ca. 1200 m, 22°34’51.74”N, E 101°6’31.57”E, 18 May 2016, Lei Jiang & Hua Peng JL00363 (SYS!).

Figures

FIGURE 1. Asplenium cyrtosorum.—A. Habit.—B. Abaxial view of portion of frond.—C. Adaxial view of lamina.—D. Adaxial view portion of lamina showing shape and color of adaxial side of rachis.—E. Abaxial view portion of lamina showing shape and color of abaxial side of rachis.—F. Abaxial view of upper portion of lamina.—G. Adaxial view of pinnae showing venation.—H. Abaxial view of pinnae showing sori distribution.—I. Upper portion of lamina showing gemma.—J. Fiddlehead.—K. Lower portion of petiole showing petiole scales.

FIGURE 2. Asplenium cyrtosorum.—A. Habit.—B. Lateral pinna.—C. Terminal pinna.—D. Rhizome scale (Drawn by Lei Jiang & Ke- Wang Xu based on the isotype at MO).