Leptochilus bolikhamsaiensis Liang Zhang, Khamphanh Thepkaysone & Zhuo Zhou, 2024

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 : 217-218

1. Leptochilus bolikhamsaiensis Liang Zhang, Khamphanh Thepkaysone & Zhuo Zhou , sp. nov. ( Fig. 3 ).

Type: LAOS. Bolikhamsai: Viengthong District, near Samsok Noi, elev. 977 m, 18.57°N / 104.62°E, on limestone rocks in disturbed rainforest, 30 April 2019, Zhuo Zhou, Khamphanh Thepkaysone, Mouachanh Xayvue, Kosorn Sorsoulithanh, Liang Zhang LZ156 (holotype KUN-1576320!, isotype KUN-1576319!).

Diagnosis: Leptochilus bolikhamsaiensis is distinguished from other species by its small habit with laminae 6‒15 cm, and oblong sori.

Plants perennial, evergreen. Rhizome creeping, ca. 2.1–2.9 mm in diam., dorsiventrally flattened, densely scaled, with many short roots; scales brown, clathrate, membranous, margins entire or sparely denticulate, slightly spreading, 0.6–1.6 × 0.4–0.7 mm. Fronds monomorphic or slightly dimorphic, (0.3–) 0.9 to 1.8 cm distant, 16–23 cm long; petioles stramineous, 6–14 cm long, ca. 0.5–0.8 mm in diam. at middle, slightly winged at distal part; rachis distinctly winged, 2.1–2.6 mm wide at the distal part, 1.7–1.9 mm at base. Laminae oblong-ovate, deeply 1-pinnatifid, 6–15 × 7–10 cm, widest at middle or below middle of lamina, chartaceous, brown when dry, glabrous, margins of lobes entire, slightly repand. Lobes (1–)5–6 pairs, narrowly lanceolate, apex acuminate, 4.3–5.2 × 0.7–0.9 cm, basal portions of lobes narrowed, ascending upward, midribs of lobes at angles of 47–72(–90) degree with rachis, distal pair of lobes slightly narrowed, opposite or slightly alternate, lobe base ca. 0.4–0.9 cm distant with each other. Midribs slightly raised, lateral veins invisible. Sori oblong, (4–)9–11 on each side of midrib, 1–3 × 0.7–1.0 mm, centers ca. 3–5(–9) mm apart from one another.

Additional specimen examined: LAOS. Na be, Provincia, December 1930, collectors unknown, a number labeled as “4.107” may be the collecting number ( US 1595356!).

Distribution and habitat: Leptochilus bolikhamsaiensis was initially collected in Laos in 1930, but its exact location was not specified. Currently, only one population in Viengthong District of Bolikhamsai Province is known to us. The individuals of the species were observed growing exclusively on limestone rocks in the rainforest. It is likely that the species occurs in other karst regions in central Laos.

Etymology: The species epithet is derived from the name of Bolikhamsai Province, Laos, where the species is found.

Note: Leptochilus bolikhamsaiensis is morphologically the smallest species, regarding to the “ L. ellipticus complex”. However, according to the phylogenetic analysis, this species forms an isolated clade within the genus, and its relationships to other species of the genus, particularly to the L. ellipticus clade, remain unclear.

Figures

FIGURE 3. Leptochilus bolikhamsaiensis Liang Zhang, Khamphanh Thepkaysone & Zhuo Zhou,—A. Habitat.—B.Adaxial lamina.—C. Abaxial lamina with five pairs of lobes.—D.Abaxial lamina with three pairs of lobes.—E. Rhizome with a fiddlehead. Photo credit: Liang Zhang.