Leptochilus wusugongii Liang Zhang & 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 : 231-233

11. Leptochilus wusugongii Liang Zhang & Li Bing Zhang , sp. nov. ( Fig. 13 ).

Type: LAOS. Luang Prabang Province: Luang Prabang District, state water supply protected area, outside Luang Prabang City, 500–700 m, on limestone rock in primary forest, 31 October 2011, Su-Gong Wu, Xun Gong, Bo Ding, Onevilay Souliya & Khamphanh Thepkaysone WS-2591 (holotype KUN-1229050!, isotype MO-6351014!).

Diagnosis: Leptochilus wusugongii is characterized by lamina thickly chartaceous, lobes large, 3.5–4.9 cm in width.

Plants perennial, evergreen. Rhizome creeping, ca. 0.6–1.2 mm in diam., dorsiventrally flattened, scaly; scales appressed, slightly spreading at rhizome apex, membranous, margins entire, brown, (1.6–)2.1–3.5 (–4.6) × (0.4–) 0.8– 1.2 mm. Fronds monomorphic, (43–) 70–120 cm long, petiole slightly longer than lamina; petioles stramineous, (26–) 38–66 cm long, ca. 2.5–4.1 mm in diam. at middle, wingless; rachises wingless, and only slightly winged at distal rachis and the connecting part between rachis and lobe. Laminae broad elliptic, deeply 1-pinnatifid, (15–)33–55 × 24–40 cm, widest at middle or below middle of laminae, thickly chartaceous, brown when dry, glabrous, margins of lobes entire, slightly repand. Lobes 2–6 pairs, lanceolate, apex acuminate, 14–18 × 3.5–4.9 cm, basal portions of lobes narrowed, ascending upward, midribs of lobes at angles of 39–79 degree with rachis, distal pair of lobes slightly narrowed, alternate or nearly opposite, lobe base ca. 3.7–4.2 cm distant with each other. Midribs distinctly raised, veins slightly visible. Sori linear, 18–25 on each side of midrib, centers ca. 5–7 mm apart from one another, 1.7–2.2 × 0.5–0.8 mm. close to midrib, ca. 3–7 mm distant to the lobe margins.

Additional specimens examined: LAOS. Luang Prabang Province: Luang Prabang District, state water supply protected area, outside Luang Prabang City, 610 m, 19.83°N / 102.15°E, on limestone rock, 13 May 2019, Zhuo Zhou & Liang Zhang LZ403 (KUN!). Vientiane Province: Vang Vieng District, Phou Houat Pha Tang Village, 600 m, 19.07°N / 102.41°E, in primary forest, 15 November 2007, Su-Gong Wu, Jian-Ying Xiang, En-De Liu, Somsanith Bouamanivong, Onevilay Souliya WS-424 (KUN!).

Distribution and habitat: Leptochilus wusugongii was discovered in two provinces in northern Laos. There is a possibility that this species is distributed in neighboring areas, such as northern Vietnam and southern Yunnan, China. This species was exclusively observed thriving on limestone in the primary forest.

Etymology: Leptochilus wusugongii is named in honor of Professor Su-Gong Wu, distinguished pteridologist and one of the collectors of the new species. Professor Wu diligently collected a significant number of fern specimens in Southeast Asia, contributing greatly to our understanding of the fern diversity in this region.

Note: Leptochilus wusugongii is morphologically most similar to L. sinovietnamica in having large habit, broad lobes, and typically 3–4 pairs of lobes. However, it differs from L. sinovietnamica by having a thicker texture of laminae. To better define the morphological boundaries between these two species, additional field observations and specimen examinations are necessary. Our phylogenetical study resolved L. wusugongii as sister to L. sinovietnamica , displaying distinct genetic divergence ( Fig. 1 ). This discovery adds a new species to the Vietnam clade, which is recognized as one of the earliest-diverging clades within Leptochilus , as defined in Zhang et al. (2019).

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 13. Leptochilus wusugongii Liang Zhang & Li Bing Zhang,—A. Habit.—B. Rhizome.—C. Rhizome scales.—D. Portion of abaxial lobe showing sori.—E. Portion of adaxial lobe. Photo credit: Liang Zhang.