Leptochilus locii Liang Zhang, N.T. Lu & Li Bing Zhang

Zhang, Liang, Lu, Ngan Thi, Zhou, Xin-Mao, Zhou, Zhuo, Thepkayson, Khamphanh, Luong, Thien Tam & Zhang, Li-Bing, 2024, Exploring the diversity of the Java fern genus Leptochilus (Polypodiaceae) in the Indo-Burma Biodiversity Hotspot, Phytotaxa 659 (3), pp. 213-235 : 222-224

5. Leptochilus locii Liang Zhang, N.T. Lu & Li Bing Zhang , sp. nov. ( Fig. 7 ).

Type: VIETNAM. Quang Binh: Phong Nha Ke Bang National Park, Tan Traih, elev. 700 m, 17.39°N /106.20°, on rocks in limestone mountains, 6 November 2014, Li Bing Zhang, Liang Zhang & Ngan Thi Lu 7352 (holotype VNMN, isotype CDBI!).

Diagnosis: Leptochilus locii is characterized by its dimorphic fronds, fertile fronds approximately four times longer or more than sterile fronds, fertile fronds long-petiolated, and laminae thickly chartaceous.

Plants perennial, evergreen, lithophytic. Rhizome long creeping, ca. 1.8–2.9 mm in diam., dorsiventrally flattened, scaled, with a few short phyllopodia and roots. Apex of rhizome and basal petiole densely scaly, scales lanceolate, base enlarged, (0.7–)1.2–3.3 × 0.4–1.4 mm, brown, basifixed, concolorous, margin entire, apex long acuminate. Fronds dimorphic, fertile fronds much longer than sterile fronds. Sterile fronds 9–12 cm tall, laminae slightly longer than or the same length as petioles; laminae triangular-ovate, base truncate, apex obtuse-acuminate, 4–7 cm long, 2.9–3.5 cm wide near base, thickly chartaceous, glabrous; petioles stramineous, grooved adaxially, glabrous, 0.7–0.9 mm in diam., 5–7 cm long. Fertile fronds 19–25 cm tall, petioles much longer than laminae; laminae ovate, margins entire, base cuneate, apex long acuminate, (1.6–) 3.9–4.5 cm long, (0.8–) 1.5–1.7 cm near base, thickly chartaceous, glabrous; petioles stramineous, grooved adaxially, glabrous, 0.9–1.1 mm in diam., 18–20 cm long. Veins anastomosing, lateral vein distinct, veinlets visible. Sori linear, ca. 0.5–1.1 mm from margins and 0–0.2 mm from midrib, 9–12 on each side of midrib, 0.8–1.1 cm long, 0.9–1.1 mm wide when mature, at angles of 42–50 degree with midribs, centers ca. 2–3 mm apart from one another. Paraphyses absent.

Additional specimens examined: VIETNAM. Quang Binh: Bo Trach District, Hung Trach, Phong Nha-Ke Bang National Park, 150–200 m, 17.50°N /106.28°, on limestone rock in slightly logged primary forest, 12 December 2004, S.-K. Wu, L.K. Phan, X. Gong, J.-Y. Xiang, V.T. Nguyen & K.S. Nguyen WP-1077 (KUN!, MO!).

Distribution and habitat: Three populations of Leptochilus locii were discovered in central Vietnam, and the species was exclusively observed growing on limestone rock.

Etymology: Named in honor of Professor Phan Ke Loc of Hanoi University of Science, in recognition of his significant contributions to the fern flora of Vietnam.

Note: Leptochilus locii is most similar to L. ovatus by sharing features such as dimorphic fronds, sterile fronds ca. 4–6 times larger than fertile fronds, and petioles of fertile fronds ca. 8–10 times longer than fertile laminae. However, the new species differs from the latter in having triangular-ovate sterile lamina, and lamina base slightly cordate to truncate. In contrast, L. ovatus has elliptic-ovate to broadly elliptic sterile lamina, and sterile lamina base gradually decrescent.

Figures

FIGURE 7. Leptochilus locii Liang Zhang, N.T. Lu & Li Bing Zhang,—A. Habitat.—B. Adaxial view of sterile frond.—C. Habit.—D. Abaxial view of sterile frond.—E. Abaxial view of fertile lamina.—F. Adaxial view of fertile lamina. Photo credit: Liang Zhang.