Polystichum sunhangii Liang Zhang, Yong Ling Qiu & 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 : 21-22

Polystichum sunhangii Liang Zhang, Yong Ling Qiu & Li Bing Zhang , sp. nov. ( Fig. 2 )

Type:— CHINA. Xizang: Medog County, Motuo Town , Yarang , elev. ca. 1200 m, 29°14’N / 95°16’E, on slopes in evergreen forests, 26 June 2021, Liang Zhang, Xia Wan, Jianjun Yang & Wanglin Zhao 4582 (holotype KUN-1576004! ; isotype PYU!) .

Diagnosis: Polystichum sunhangii is most similar to P. attenuatum by having bipinnate laminae and bulbils on subapical rachis, but differs from later in the location of bulbils, which are found on the every distal costa.

Plants perennial, evergreen, terrestrial. Rhizome short, erect, ca. 10–15 mm in diam., lower part with many glabrous and dark brown roots, upper part densely scaly, scales concolorous or middle part slightly dark; scales dimorphic, large scales ovate or lanceolate, entire, apex acuminate, 5.1–7.2 × 1.1–3 mm, small scales lanceolate or linear-lanceolate, 2.3–3.5 × 0.6–1.3 mm. Frond caespitose, 60–100 cm tall; petiole stramineous, 26–35 cm, 1–3 mm in diam. at middle, adaxially canaliculated, base densely scaly, light brown or reddish brown; scales dimorphic, large scales ovate-lanceolate, 2.9–4.1× 1.1–2.1 mm, chartaceous, margins entire, small scales lanceolate or linear-lanceolate, 1.8–3.1 × 0.4–1.2 mm. Lamina bipinnate, oblong - lanceolate, 39–66 × 16–23 cm, thickly papery, apex acuminate, slightly contracted towards base; rachises stramineous, 36–63 cm long, ca. 1–3 mm in diam. at middle, adaxially sulcate, covered with lanceolate brown scales, scales dimorphic, similar to petiole scales, large scales spare, with 1 proliferous bulbil near apex. Pinnae 15–22 (–37) pairs, alternate, pinnate to pinnatifid upwards, shortly petiolate, lanceolate, apices acute, mostly attached at right angles to rachis, upper pinnae slightly ascendant, basal 1 or 2 pairs angled basiscopically with rachis, middle pinnae 9–13.5 × 1.8–3.8 cm, the upper basal pinnae longer than rest, the lower basal pinnae slightly shorter than rest; pinnules rhombic-ovate, 6–11 pairs, apices obtuse, acroscopic bases with distinct or indistinct deltoid auricles, basiscopic side slightly curved, margins shallowly toothed, teeth with aculeate tip or spinulose, acroscopic auriculate pinnules sometimes shallowly lobed, adaxially glabrous, abaxially sparsely covered with lanceolate or subulate microscales, microscales light brown or brown, apex acuminate; venation free, lateral veins pinnate, visible abaxially, indistinct adaxially. Sori large, round, terminal on shorter veinlets, in one row on each side of midrib, medial, centers of sori ca. 0.1–0.5 cm from pinnule margins, 2–10 on acroscopic side, 0–6 on basiscopic side; indusia present, round, membranous, entire.

Additional specimens examined (paratype):— CHINA. Xizang: Medog County, Motuo Town , elev. ca. 1920 m, 29°11’N / 95°19’E, open area in forests, 26 June 2021, Liang Zhang, Xia Wan, Jianjun Yang & Wanglin Zhao 4548 ( KUN!) .

Geographical distribution:—The species is currently only found in Medog County, Xizang, China, and may be endemic to the region.

Ecology:— Polystichum sunhangii was observed to be a terrestrial plant in open areas of evergreen forests, growing at elevations between 1200 and 1920 m.

Etymology:—In honor of Prof. Hang Sun, who has been working on plant diversity in Medog since 1992.

Vernacular name:—IJǟff̎ (sun hang er jue).

Notes:—While bulbils on the rachis are not uncommon in Polystichum , they were rarely found on the costae ( Fraser-Jenkins et al. 2018). In contrast, all mature pinnae of P. sunhangii have bulbils on distal costae, which has not been documented in any other species of Polystichum so far. Morphologically, P. sunhangii is also similar to P. chunii and P. lentum in the presence of bulbils on the rachis. Our reconstructed phylogeny confirmed the monophyly of P. attenuatum , P. chunii , P. lentum (three samples from Medog were added), although the support was weak (MLBS=56%, BIPP=0.73). The relationships among the three species remain unclear. Polystichum sunhangii is closely related to the three species with distinct divergence.

Figures

FIGURE 2. Polystichum sunhangii.—A. Habit.—B. Adaxial view of middle portion of lamina.—C. Fiddlehead (young leaf).—D. Distal rachis, showing a bulbil.—E. Abaxial view of portion of pinna, showing sori.—F. Abaxial view of pinnae, with blue arrows indicating bulbils on costae.