Polystichum xinfeniae Liang Zhang, W.B. Ju & 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 : 24-26

Polystichum xinfeniae Liang Zhang, W.B. Ju & Li Bing Zhang , sp. nov. ( Fig. 4 )

Type:— CHINA. Xizang: Medog County, Beibeng Xiang , from Aniqiao to Laohuzui , elev. ca. 1200 m, 29°19’N / 95°10’E, on wet cliffs in the dense forests, 25 June 2021, Liang Zhang, Xia Wan, Jianjun Yang & Wanglin Zhao 4538 (holotype KUN-1575999! ; isotype PYU!) .

Diagnosis: Polystichum xinfeniae closely resembles P. obliquum in terms of the shape of its pinnae and the irregularly toothed pinna margins. However, it can be differentiated from the latter by having up to 30 pairs of pinnae.

Plants perennial, evergreen, terrestrial. Rhizome short, erect, ca. 10–15 mm in diam., with many glabrous and dark brown roots, densely scaly, scales ovate-lanceolate, concolorous, reddish brown, 4–7 × 1.5–2.5 mm. Frond caespitose, 3–8 per rhizome, 36–71 cm tall; petiole stramineous, 11–22 cm, 1–3 mm in diam. at middle, adaxially canaliculated, base densely scaly; petiole scales similar to rhizome scales, light brown or reddish brown, ovate-lanceolate, 3.5–6 × 1–2 mm, margins entire. Lamina lanceolate, once pinnate, thickly papery, 25–54 × 3.5–5.1 cm, apex acuminate, base the same size or slightly contracted; rachises stramineous, 24–46 cm long, ca. 1–3 mm in diam. at middle, without proliferous bulbils, sparsely covered with lanceolate brown scales, adaxially sulcate. Pinnae 18–30 (–40) pairs, oblong or falcate-lanceolate, middle pinnae 2.5–3.5 × 0.6–1.1 cm, alternate, slightly ascendant, basal most pairs the same length as long as middle ones, shortly stalked, apices acute or obtuse, acroscopic margins irregularly toothed or slightly repand, basiscopic margins cuneate and entire, bases obviously asymmetrical, acroscopic base often with deltoid or nearly deltoid auricles, distal basiscopic margins slightly curved upward; adaxially surface green when fresh, dull green when dry, glabrous, abaxially sparsely covered with lanceolate or subulate microscales, microscales narrowly lanceolate, apex acuminate, brown, 0.5–1.1 × 0.1–0.2 mm, light brown or brown; venation pinnate, lateral veins free, visible or distinct abaxially, indistinct adaxially. Sori round, small, terminal on shorter veinlets, in one row on each side of midrib, medial, 3–9 on acroscopic side, 3–6 on basiscopic side; indusia round, peltate, membranous, brown, entire, fallen off early.

Additional specimens examined (paratypes):— CHINA. Xizang: Medog County, Beibeng Xiang , elev. ca. 1530 m, 29°20’N / 95°10’E, on wet cliffs in forests, 15 October 2017, Liang Zhang, Wenbin Ju & Hengning Deng 2111 & 2113 ( KUN!) .

Geographical distribution:—The species is currently only found two large populations with about 50 individuals in Medog County, Xizang, China, and may be endemic to the region.

Ecology:— Polystichum xinfeniae was observed to be lithophytic on wet cliffs in dense evergreen forests, growing at elevations between 1200 and 1530 m. The two populations are near the Duoxionghe river. Thus, the high humidity and shade are crucial for maintaining the two populations.

Etymology:—In honor of Prof. Xinfen Gao, who is one of the earliest female botanists to explore the plant diversity in Medog.

Vernacular name:—ÊḞff̎ (xin fen er jue).

Notes:— Polystichum xinfeniae is morphologically most similar to P. obliquum . The two species can be distinguished by the fact that P. xinfeniae has 18–30 pairs of pinnae, with pinnae close or even overlapping each other, while P. obliquum has 7–18 pairs of pinnae, and pinnae obviously spaced to each other. The two species were resolved as sister to each other in our reconstructed phylogeny but with distinct genetic divergence. Some individuals of P. xinfeniae (e.g., L. Zhang et al. 2113) have narrow pinnae, making them easily confused with P. acutidens Christ (1902: 259) . However, P. acutidens has long teeth regularly along pinna margins, while P. xinfeniae has short or long teeth irregularly along pinna margins.

Figures

FIGURE 4. Polystichum xinfeniae.—A. Habit.—B. Petioles.—C. Abaxial pinnae, showing sori.—D. Upper portion of adaxial lamina.— E. Middle portion of adaxial lamina.