Polystichum wusugongii Liang Zhang, Xin M. Zhou & Li Bing Zhang, 2023

Qiu, Yong-Ling, Yang, Jian-Jun, Zhou, Xin-Mao, Ju, Wen-Bin, Zhang, Li-Bing, He, Zhao- Rong & Zhang, Liang, 2023, Three new species of Polystichum (Dryopteridaceae) from Xizang, China based on morphological and molecular evidence, Phytotaxa 618 (1), pp. 18-30 : 22-24

Polystichum wusugongii Liang Zhang, Xin M. Zhou & Li Bing Zhang , sp. nov. ( Fig. 3 )

Type:— CHINA. Xizang: Medog County, Motuo Town , elev. ca. 2240 m, 29°17’N / 95°22’E, near a stream at forest margins, 18 June 2021, Liang Zhang, Xia Wan, Jianjun Yang & Wanglin Zhao 4219 (holotype KUN-1575998! ; isotype!) .

Diagnosis: Polystichum wusugongii is most similar to P. hookerianum by having pinnate laminae and lanceolate pinnae often longer than 5 cm. However, it can be distinguished by the presence of only one row of sori on each side of the midrib and the free venation.

Plants perennial, evergreen, terrestrial. Rhizome short, erect, ca. 6–15 mm in diam., with many glabrous and dark brown roots; densely covered with ovate-lanceolate brown scales, scales 4.0–6.1× 1.1–2.0 mm. Frond caespitose, 2–5 per rhizome, 46–97 cm tall; petiole stramineous, 11.5–39.5 cm, 1–3 mm in diam. at base, adaxially canaliculated, base scaly, scales light brown, linear-lanceolate, 3.1–4.2 × 1.0– 2.1 mm, scattered, margins entire. Lamina once pinnate, lanceolate, thickly papery, 21–64 × 9–12 cm, apex acuminate, slightly shortened at base; rachises stramineous, 19–60 cm long, ca. 1.1–3.2 mm in diam. at middle, sparsely covered with lanceolate brown scales, adaxially sulcate. Pinnae 21–27 pairs, middle pinnae 3.9–9.5 × 0.8–1.5 cm, alternate, slightly ascendant, shortly stalked, lanceolate, apices acuminate or rarely caudate, bases cuneate and asymmetrical, basiscopic proximal margins entire, acroscopic margins and basiscopic distal margins irregularly to othed or repand, teeth 0.7–1.2 mm, acroscopic base of pinna distinctly auriculate; adaxially glabrous, abaxially slightly scaly; venation pinnate, lateral veins free, visible or distinct abaxially, indistinct adaxially. Sori round, terminal on shorter veinlets, in one row on each side of midrib, medial, centers of sori ca. 0.5–0.7 cm from pinna margins, 18–24 on acroscopic side of middle pinnae, 14–20 on basiscopic side of middle pinnae; indusia present, round, membranous, entire, white when young, dark brown when mature; 64 spores per sporangium.

Additional specimens examined (paratype):— CHINA. Xizang: Medog County, Beibeng Xiang, near Hanmi lodge, elev. ca. 2100 m, 29°21'N / 95°7'E, terrestrial in evergreen forests, 24 October 2021, Liang Zhang 4709 ( KUN! & PYU!) .

Geographical distribution:—Currently, Polystichum wusugongii is only found in Medog County, Xizang, China and may represent a species endemic to Xizang, China.

Ecology:— Polystichum wusugongii was observed to be terrestrial in the evergreen forests or near stream at forest margins, at elevations between 2100 and 2240 m.

Etymology:—In honor of the late Prof. Sugong Wu, one of the authors of Flora Xizangica, who had started exploring plant diversity in Xizang since 1960.

Vernacular name:—Îffiff̎ (su gong er jue).

Notes:—Morphologically, Polystichum wusugongii is most similar to P. hookerianum by having larger habit compared to other species of the genus with one pinnate lamina. However, P. hookerianum is unique by its anastomosing venation and more than one row of sori on either side of the midrib. Phylogenetically, these two species were resolved as sister to each other but with distinct divergence between them. In Medog, P. hookerianum was found at elevations below 1500 m, while P. wusugongii has been found at elevations above 2000 m.

Figures

FIGURE 3. Polystichum wusugongii.—A. Habit.—B. Fiddlehead (young leaves).—C. Lower portion of plant.—D.Abaxial view of lower portion of lamina.—E. Adaxial view of portion of lamina.—F. Abaxial view of upper portion of lamina.—G. Abaxial view of portion of lamina showing sori.