Selliguea wusugongii Liang Zhang, X.P.Fan & Li Bing Zhang, 2021

Fan, Xue-Ping, Zhang, Lin, Zhang, Li-Bing & Zhang, Liang, 2021, Selliguea wusugongii (Polypodiaceae), a new fern species from southeastern Xizang, China based on morphological and molecular evidence, Phytotaxa 480 (1), pp. 57-68 : 59-63

Selliguea wusugongii Liang Zhang, X.P.Fan & Li Bing Zhang , sp. nov. ( Figs. 2 & 3 ).

Type:— CHINA. Xizang: Medog County, Beibeng Xiang , Deergong Village , elev. 1700–1800 m, 29°10’N / 95°08’E, on tree trunk in broadleaved evergreen forests of primary vegetation, 24 November 2018, Liang Zhang 2955 (holotype KUN1497728 !; isotypes KUN & CDBI!) .

Diagnosis:— Selliguea wusugongii is most similar to S. stenopteris by having narrow lamina and marginal and rounded sori, but differs the latter in having scales considerably more scattered on the rhizome and a monomorphic graminiform frond up to 40 cm long.

Plants perennial, evergreen, epiphytic. Rhizome long creeping, ca. 0.8–1.2 mm in diam., dark brown when dry, with many hairy roots and a few short phyllopodia, internodes of phyllopodia 0.8–1.4 cm long, cross section of rhizome with 4–10 vascular strands (amount of vascular strands are quite variable from different individuals, see C, D, E of figure 3), sclerenchyma strands 13–25; rhizome and phyllopodia distinct scaly, rhizome scales lanceolate, scattered and exserted, 1.6–4.2 mm long, 1.1–1.3 mm wide at the widest, light brown, peltate, basal parts appressed, upper middle parts spreading, apex acuminate, margin entire, scales of phyllopodia similar to rhizome scales but smaller. Frond monomorphic, (11–) 25–40 cm tall, 0.8–1.1 mm wide; petiole stramineous, wingless part (1.2–) 3.5–9 cm long, 0.4–0.6 mm wide, with a few scales on base, slighted grooved, gradually winged at distal part. Lamina long needlelike, simple, slightly grooved adaxially, margins entire and revolute when dry, (9–) 21–32 cm long, 0.8–1.1 mm wide, widest at middle of lamina, papery, dark green in the wild, light green when dry, glabrous; midrib stramineous when dry, slightly raised, up to half width of laminae, sometimes partially covered by revolute laminae. Veins invisible. Sori on upper part of lamina, oblong, (4)6–8 on each side of midrib, 2.0– 2.3 mm long, 0.6–0.8 mm wide, at least covering half width of laminae, slightly out of lamina margins, basal pairs of sori nearly opposite, upwards alternate and distant, ca. 0.4–1.1 cm apart from one another. Paraphyses absent.

Geographical distribution:— Currently, Selliguea wusugongii is found in Medog County, Xizang, China , and nearby regions, may represent a species endemic to southeast Xizang.

Ecology: — Selliguea wusugongii was observed to grow on tree trunks in primary forests, at elevations between 1700 and 1800 m. The rhizomes are partially covered by some mosses such as Metzgeria conjugata Lindberg (1875: 495) .

IUCN Red List category: —Only two populations with about 22 individuals of Selliguea wusugongii were found. The status of the new species can be classified as Critically Endangered (CR), based on current information and following the IUCN (The International Union for Conservation of Nature and Natural Resources) guidelines ( IUCN, 2019), but more extensive fieldwork focusing on the tree trunks in the nearby mountains is needed to accurately assess its conservation status.

Etymology: — Named in honor of Prof. Wu Sugong, pteridologist based at KUN, for his contributions to the taxonomy of ferns, and especially to the fern flora of Xizang.

Taxonomic notes: — Two collections from a single locality (R.S. Rao 17766 & 1766A) from the adjacent area of Medog County were referred to Selliguea bisulcata by Dixit & Nair (1977), which should be conspecific to S. wusugongii . These were discussed by Fraser-Jenkins (2008, 2012) and re-identified as either S. enervis or S. subsparsa , and were assigned the IUCN category of Critically Endangered (CR). Fraser-Jenkins (pers. comm. 11.2020) now identifies them as being the same as S. wusugongii .

Figures

FIGURE 2. Selliguea wusugongii.—A. Habitat.—B. Rhizome and scales.—C. Upper part of adaxial lamina.—D. Portion of adaxial lamina.—E. Upper part of abaxial lamina.—F. Portion of abaxial lamina showing sori.

FIGURE 3. Selliguea wusugongii.—A. Fronds from holotype.—B. Scale of phyllopodium.—C. Rhizome scale.—D-F. Cross sections of rhizome showing vascular tissues and sclerenchyma strands.