Polystichum hagiangense Li Bing Zhang, Ngan T. Lu & Liang Zhang, 2014

Lu, Ngan Thi, Zhang, Liang & Zhang, Li-Bing, 2014, Polystichum hagiangense (subg. Haplopolystichum; Dryopteridaceae), a new fern species from Ha Giang Province, northern Vietnam, Phytotaxa 175 (5), pp. 293-297 : 293-295

Polystichum hagiangense Li Bing Zhang, Ngan T. Lu & Liang Zhang , sp. nov. ( Figure 1 )

Polystichum hagiangense is most similar to P. minutissimum Li Bing Zhang & H.He (2009: 353) by having a small habit (lamina 3.6–5.8 × 1.0– 1.6 cm) and the leaves are appressed to the substrate, but the first has the widest part of the lamina close to the base and ovate and larger pinnae (5.3–8.2 × 3.2–5.8 mm). In contrast, the latter has the widest part of the lamina above the middle and nearly rectangular, smaller pinnae (2.9−5.8 × 2.8−4.5 mm).

Type:— VIETNAM. Ha Giang Province: Bat Dai Son Community, Bat Dai Son Provincial Protected Area , ridge north of Bat Dai Son border station, 23°09’11’’N / 104°59’06’’E, on sheer limestone cliff, 1290 m, 11 February 2001, D. K . Harder, N. T . Hiep, L. V . Averyanov & P. K . Loc 6162 (holotype HN!, isotypes LE, MO) .

abaxial lamina surface.

Plants perennial, evergreen. Rhizomes ascending, 0.4–0.7 cm, ca. 5 mm in diam., with remnant bases of old petioles, scaly; scales broad lanceolate, 1.3–1.8 × 0.50–0.72 mm, brown, margins nearly entire, with a few short outgrowths; roots not seen. Leaves caespitose, 6–10 per rhizome, appressed to substrate and slightly ascending, 5.5–9.5 cm long; petioles green, 1.8–5.5 cm, 0.5–1 mm in diam. at the middle, adaxially canaliculate, scaly; basal petiole scales lanceolate, chartaceous, 1.5–1.8 × 0.6–0.7 mm, brown, concolorous, apices acuminate, margins nearly entire or slightly ciliate, with irregular dentate outgrowths; distal petiole scales similar to basal petiole scales but narrower, 0.8–1.3 × 0.4–0.5 mm, chartaceous, brown, apices caudate, margins with short outgrowths. Laminae oblanceolate, once pinnate, 3.6–5.8 × 1.0– 1.6 cm, apices acute, basalmost two pairs of pinnae slightly narrowed toward base; rachises ca. 0.6 mm in diam. at middle, apices without proliferous bulbil, green (same color as pinnae) when fresh, turning yellowish green when dry, adaxially sulcate, scaly abaxially; rachis scales subulate to linear, brown, (0.4–)1.0– 1.4 mm long, base 0.11–0.25 mm wide, differing in length, chartaceous, margins sparsely toothed, apices caudate. Pinnae 8–10 pairs, ovate, 5.3–8.2 × 3.2–5.8 mm, basalmost 0–2(–3) pairs slightly smaller toward lamina base, nearly 1/2 to 4/5 as long as middle ones, papery, shortly petiolate (petioles ca. 0.3 mm long), basiscopic margins at angles of 80–100 degree with rachis, alternate, apices rounded, bases rounded, distal acroscopic margins shallowly undulate and densely covered with microscales similar to those on abaxial lamina surface, undulations 2–3, ca. 0.25 mm tall in middle and non-mucronate, acroscopic bases auriculate, auricles rounded and 0.5–1.1 × 0.1–0.3 mm, basiscopic margins shallowly undulate or nearly entire and densely covered with microscales similar to those on abaxial lamina surface, curved; adaxial surface green when fresh, dull green when dry, both adaxial and abaxial surfaces covered with microscales; microscales on adaxial surface sparse, linear, light brown, 0.2–0.5 mm long, 0.10–0.13 mm wide at base; microscales on abaxial surface dense, linear or subulate, brown, 0.35–1.50 mm long, 0.11–0.15 mm wide at base, basal portion with 0–2 short outgrowths; venation pinnate, visible abaxially and slightly obscure adaxially, lateral veins free, single or forked. Basal two pairs of pinnae sterile; sori terminal on lateral veins, 1–3 on acroscopic side of fertile pinnae, 0–3 on distal basiscopic side of fertile pinnae, ca. 1 mm in diam., closer to pinna margins than to midrib (centres of sori 1.0– 1.8 mm from pinna margins, 1.0– 1.8 mm from midrib), centers ca. 1.4–2.2 mm apart from one another; indusia not seen.

Geographical distribution:— Polystichum hagiangense is only known from Bat Dai Son Community in Ha Giang Province, northern Vietnam. It is possible that the species occurs in additional limestone mountains around Bat Dai Son in Ha Giang Province and even in adjacent Yunnan Province of China yet to be explored. However, our recent field investigation outside of the type locality in the same community failed to locate this species.

Ecology:— Polystichum hagiangense grows from slightly disturbed forest on lower slopes below limestone cliffs, to disturbed forest margin near agricultural fields, and to ridge tops of disturbed forest and rocky outcrops, at an elevation of 1150–1330 m.

IUCN Red List category:—Only a few individuals of Polystichum hagiangense were seen in the field (L. V. Averyanov and D. Harder; pers. comm. to L.-B. Zhang). The status of the new species clearly should be classified as CE – Critically Endangered category based on current information and following the IUCN (The International Union for Conservation of Nature and Natural Resources) guidelines (IUCN 2008), but a more extensive search is needed to accurately assess the conservation status.

Etymology:—The species epithet is from the Vietnamese spelling, hagiang, the name of the province in northern Vietnam where the type was collected, and the Latin suffix -ense, of origin or place.

Figures

FIGURE 1. Polystichum hagiangense—A. Habitat with appressed leaves shown as being erect. B. Portion of rachis with pinna. C. Scales from basal portion of the petiole. D. Scales from distal portion of the petiole. E. Scales from middle portion of rachis. F. microscales from