Leptochilus vietnamensis 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 : 230-231

10. Leptochilus vietnamensis Liang Zhang, N.T. Lu & Li Bing Zhang , sp. nov. ( Fig. 12 ).

Type: VIETNAM. Hoa Binh: Lac Son District, Ngoc Son Ngo Luong Nature Reserve, elev. 624 m, 20.43°N / 105.34°E, on a tree trunk in limestone mountains, 20 November 2013, Li Bing Zhang, Liang Zhang & Ngan Thi Lu 6334 (holotype VNMN, isotype CDBI!).

Diagnosis: Leptochilus vietnamensis differs from other species in the genus by the combination of having long petioles in both fertile and sterile fronds, sterile laminae that can reach up to 30 cm in length, and fertile laminae that are less than half the length of the sterile laminae.

Plants perennial, evergreen, epiphytic. Rhizome long creeping, robust, ca. 2.5–5.0 mm in diam., dorsiventrally flattened, scaled, with a few short phyllopodia and roots.Apex of rhizome and basal petiole densely scaly, scales subulatelanceolate, 1.8–2.9 × 0.4–0.7 mm, brown, basifixed, concolorous, clathrate, margins entire or sparely denticulate, apex acuminate. Fronds dimorphic, fertile fronds longer than sterile fronds. Sterile fronds (15–) 30–40 cm tall, petiole shorter than lamina; laminae ribbon-lanceolate, margins entire, slightly repand, base cuneate, apex acuminate, 21–30 cm long, (2.5–) 6–7 cm wide at middle, chartaceous, glabrous; petioles stramineous, grooved adaxially, glabrous, 1.5–2.2 mm in diam., (3–) 5–9 cm long. Fertile fronds 21–30 cm tall, petiole usually longer or the same length as lamina; laminae elliptic-lanceolate to ovate-lanceolate, margins entire, base cuneate, apex long acuminate, (8–) 10–15 cm long, 3–5.5 cm wide at middle, chartaceous, glabrous; petioles 1.4–2.1 mm in diam., (8–) 12–15 cm long. Veins anastomosing, lateral vein distinct, veinlets visible. Sori linear, reach lamina margins, 25–42 (–50) on each side of midrib, 1.8–3.2 cm long, 1.8–2.2 mm wide when mature, at angles of 44–62 degree with midribs, centers ca. 1.5–2.1 mm apart from one another. Paraphyses absent.

Additional specimens examined: VIETNAM. Cao Bang: Tra Tinh District, Quoc Toan Municipality, Trang Hen ( Lakes District ), elev. 666–831 m, 22.75°N / 106.28°E, on tree branches in disturbed forests in mountains with solid limestone rocks, 6 April 1998, Daniel K. Harder, P.K. Loc & T.T. Tai 4254 (MO-3200946!). Hoa Binh: Tan Lac District , Lung Van Municipality , Huop village , elev. 1095–1100 m, 20.54°N / 105.18°E, epiphytic, in heavily logged primary evergreen broad-leaved forest, 29 Nov 2003, Su-Gong Wu, L.K. Phan, J.Y. Xiang, X. Gong, V.T. Nguyen & K.S. Nguyen, WP-303 (MO-5980968) ; Tan Lac District, Tam Son Community , elev. 840 m, 20.53°N / 105.18°E, 22 November 2013, Li Bing Zhang, Liang Zhang & Ngan Thi Lu 6378 ( VNMN, CDBI!) ; Mai Chau District, Pa Co Municipality , elev. 1368 m, 20.74°N / 104.89°E, epiphytic, in wet, semi-deciduous and evergreen forest, 03 December 2002, Daniel K. Harder, P.K. Lôc, B. Hall & N.Q. Hung 7701 (MO-3321598!) ; Mai Chau District, Hang Kia Municipality, Thung Ang Village , elev. 1095–1300 m, 20.72°N / 104.89°E, epiphytic, 05 December 2002, Daniel K. Harder, B. Hall, N.Q. Hung & P.H. Hoang 7782 (MO-6082983!) ; Mai Chau District, Pa Co Municipality, near Na Pai Village , elev. 1094–1200 m, 20.74°N / 104.94°E, lithophytic and epiphytic on rocks, 09 December 2002, Daniel K. Harder, T.H. Nguyên & L. V. Averyanov 8020 (MO-3321599!). Tuyen Quang: Na Hang District , Nam Chang Forest , elev. 210 m, 22.33°N / 105.42°E, on tree branches, 1 m from ground, in primary forests on sandy quartz soils, 8 March 1994, D.K. Harder, N.T. Hiêp, H.H. Schmidt & N.Q. Biñh 2412 (MO-320056!) .

Distribution and habitat: Leptochilus vietnamensis was discovered in four localities within three provinces in northern Vietnam. The species is observed growing on tree branches, trunks or on rocks.

Etymology: The specific epithet is derived from the name of the country where the new species was discovered, Vietnam.

Note: Leptochilus vietnamensis shares similarities with both L. wui and L. chingii , as the latter two both have slightly dimorphic fronds and linear sori. However, L. vietnamensis can be distinguished from them by its fertile fronds, which are shorter than its sterile fronds, and the long, ribbon-like lamina of its sterile fronds. The phylogenetic analysis resolved L. vietnamensis as sister to L. luangprabangensis , and these two species together are sister to L. chingii ( Fig. 1 ).

Figures

FIGURE 1. Phylogeny of Leptochilus based on six plastid markers (modified from Zhang et al. 2024). Orange color indicates the new species described here.

FIGURE 12. Leptochilus vietnamensis Liang Zhang, N.T. Lu & Li Bing Zhang,—A. Habit.—B. Abaxial laminae.—C. Abaxial view of portion of sterile lamina.—D. Rhizomes and petioles.—E. Rhizome scales. Photo credit: Liang Zhang.