Asplenium quangbinhense K.W.Xu, N.T.Lu & Li Bing Zhang, 2021

Xu, Ke-Wang, Lu, Ngan Thi, Zhou, Xin-Mao, Zhang, Liang & Zhang, Li-Bing, 2021, Asplenium quangbinhense sp. nov. and three new records of Asplenium (Aspleniaceae) from Vietnam, Phytotaxa 521 (2), pp. 113-120 : 114-116

Asplenium quangbinhense K.W.Xu, N.T.Lu & Li Bing Zhang , sp. nov. ( Figures 1 , 2 )

Diagnosis:—The new species is most similar to Asplenium oldhamii Hance (1866: 256) in having laminae ovate-triangular, pinna base cuneate, ultimate segments 1–2 pairs per pinna, veins not reaching pinna margins, sori 1–4 per segment, and sori and indusia linear, but the former has plants up to 35 cm tall, laminae pinnate-pinnatisect, pinnae (7–)10–15 pairs, and basal pinnae slightly reduced, whereas the latter has plants up to 20 cm tall, laminae pinnate-pinnatisect to nearly bipinnate, pinnae 5–9 pairs, and basal pinnae not reduced.

Type:— VIETNAM. Quang Binh:Minh Hoa district, Trung Hoa Commune, Hai Tien Phong Village, Nay Mountain, 530 m, 17°43’32.49”N, 105°59’36.79”E, 9 November 2014, Li-Bing Zhang , Liang Zhang & Ngan Thi Lu 7391 (holotype VNMN!, isotypes CDBI!, MO!).

Plants (20–) 32–35 cm tall. Rhizome erect, short, scaly, scales narrowly triangular to lanceolate, dark brown to black, margins entire. Fronds caespitose. Stipes slender, semiterete, 10–15 cm long, adaxially green or greyish brown near the base, sulcate, abaxially brown to blackish brown, with brown and narrowly triangular scales. Lamina ovate-triangular, (8–)12–14 × (4–) 5.5–7 cm, pinnate-pinnatisect; pinnae (7–)10–15 pairs, subopposite or alternate, shortly stalked, (0.5–) 1–3 mm, lower pinnae slightly reduced, triangular-lanceolate, 2–3 cm long, base nearly symmetrical, cuneate, margins serrate, apex acute. Costae abaxially flat to slightly raised, adaxially grooved, veins slender, green, 1–2- forked, not reaching the margin. Fronds herbaceous to papery, yellowish green on the abaxial side, dark green on the adaxial side, yellowish green or greyish green when dry, abaxially with minute, brown, lanceolate scales; rachis semiterete, brown to stramineous abaxially, sparsely scaly. Sori narrow, linear, (2.2–)2.5–6.5(–7) mm long, median to distal on subtending veins, at an angle of 5°–30° with costa; not reaching the margin, indusia yellowish green when young, greyish brown when old, linear, membranous, margins entire, usually opening toward costa, persistent.

Geographical distribution:— Asplenium quangbinhense is currently known from only two small populations in Quang Binh Province in central Vietnam. We did not find additional occurrences of the species in other provinces of Vietnam.

Habitat:—The new species grows epilithic on rocks in humid and shady conditions in an evergreen broad-leaved forests.

Etymology:—The species epithet is based on the name of the Vietnamese province Quang Binh, and the Latin suffix, -ense, of origin, referring to the type locality of the new species.

Additional specimens examined:— VIETNAM. Quang Binh: Phong Nha Ke Bang National Park: Tan Trach, limestone mountain, elev. 700 m, 17°23’32.11”N, 106°12’27.20”E, 6 November 2014, Li-Bing Zhang , Liang Zhang & Ngan Thi Lu 7353 (CDBI, MO, VNVM).

Note:—Morphologically, A. quangbinhense is most similar to A. oldhamii and could be easily misidentified as A. oldhamii in the field. Asplenium oldhamii was originally described from Taiwan Island and was reported in Vietnam by Pham (1999) and Phan (2010), but it was excluded from Vietnam by Lin & Viane (2013). The occurrence of A. oldhamii in Vietnam is suspicious. No populations were found in our three expeditions to Vietnam by us. Phylogenetically, the new species was resolved as sister to A. pseudopraemorsum ( Xu et al. 2020) , the latter being confirmed here as a new record of Vietnam. Asplenium quangbinhense can be distinguished from A. pseudopraemorsum by being a smaller plant (20–35 cm tall vs. 40–45 cm tall) and having fewer ultimate segments per pinna (1–2 vs. 4–5 pairs) and fewer scales on the abaxial side of the pinna.

Figures

FIGURE 1. Asplenium quangbinhense.—A. Habitat and habit.—B. Portion of abaxial lamina.—C. Portion of adaxial lamina.

FIGURE 2. Asplenium quangbinhense.—A. Habit.—B. Portion of lamina showing abaxial view of pinna.—C. Portion of lamina showing adaxial view of pinna.—D. Lower portion of stipe showing scales.