Leptochilus khammouanensis 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 : 221

4. Leptochilus khammouanensis Liang Zhang, Khamphanh Thepkaysone & Zhuo Zhou , sp. nov. ( Fig. 6 ).

Type: LAOS. Khammouane: Kounkham District, Na Hin, on the way to Nam Sanam Waterfall, elev. 188 m, 18.21°N / 104.51°E, on rock in forest, 2 May 2019, Zhuo Zhou, Khamphanh Thepkaysone, Mouachanh Xayvue, Kosorn Sorsoulithanh & Liang Zhang LZ202 (holotype KUN-1576321!, isotype KUN-1576322!).

Diagnosis: Leptochilus khammouanensis is distinguished in the genus by its combination of characteristics, including small habit, simple fronds, and orbicular or elongated sori.

Plants perennial, evergreen. Rhizome creeping, 2.5–4.1 mm in diam., dorsiventrally flattened, scaly, with a few short roots; scales narrowly ovate or lanceolate, brown, 1.3–3.7 × 0.4–1.1 mm, margin entire, apex acute, clathrate. Fronds monomorphic, clustered, 8–14 cm long, winged stipes shorted or nearly the same length as lamina petiole. Laminae simple, margins entire, rarely lobed, elliptic-lanceolate, abaxially not scaly, 6–9 × 1.3–1.9 cm, chartaceous or thickly herbaceous, base narrowly decrescent; petioles (0.5–) 2–8 cm, winged, wings towards petiole base, slightly scaly abaxially, scales similar to but smaller than rhizome scales; midribs distinctly raised. Venation anastomosing, main veins distinct, veinlets slightly visible. Sori separate, irregularly scattered, 0.4–1.9 × 0.3–0.5 mm, forming 2–6 irregular rows between lateral veins, orbicular or elongate, superficial, absent in marginal areoles, present in costal areoles.

Additional specimens examined: Laos. Khammouane Province: Ban Xoang (Hin Nammo National Bio-Diversity Conservation Area), elev. 156 m, 17.46°N / 105.58°E, on limestone rock in primary forests, 16 February 2017, Yu-Min Shui, Wen-Hong Chen, Phetlasy Souladeth & Liang Zhang LK136 (KUN).

Distribution and habitat: Leptochilus khammouanensis is currently only documented in two locations within Khammouane Province, located in central Laos. The species was observed growing on limestone rock in disturbed primary forests. During the extended dry season, the fronds of this species tend to shrink.

Etymology: The species epithet is from the Laotian spelling, khammouane, the name of the province in central Laos where the type was collected, and the Latin suffix - ensis, of origin or place.

Note: Leptochilus khammouanensis is morphologically most similar to some individuals of L. pteropus ( Blume 1828: 125) Fraser-Jenkins (2008: 62) , which have simple fronds. However, L. khammouanensis differs the latter by having sparely scaly to nearly glabrous petioles and rachises. Zhang et al. (2019) recognized a monospecific L. pteropus clade, which is one of the earliest-diverging lineages within Leptochilus . Our new phylogeny resolved L. khammouanensis as sister to L. pteropus , thus adding one more species to the L. pteropus clade. Our observations of L. pteropus from both basic and acidic mountains showed similar morphological similarities: variable leaf shape but with dense scales on the petioles and rachises, which can be differentiated from L. khammouanensis .

Figures

FIGURE 6. Leptochilus khammouanensis Liang Zhang, Khamphanh Thepkaysone & Zhuo Zhou,—A. Habitat.—B. Habit.—C. Portion of abaxial lamina showing sori.—D.Adaxial lamina.—E. Abaxial lamina lacking sori.—F.Abaxial lamina with sori.—G. Rhizome. Photo credit: Liang Zhang.