Leptochilus tridigitatus H.J. Wei

Wei, Hong-Jin, Qiu, Yong-Ling, Huang, Yi & Bin, Chen, 2024, Leptochilus tridigitatus (Polypodiaceae), a new fern species from Guangdong, China, Phytotaxa 650 (2), pp. 148-156 : 150-153

Leptochilus tridigitatus H.J. Wei , sp. nov. ( Figs. 2 & 3 ).

Type:— CHINA. Guangdong: Yangchun City, Huatan Forest Farm, epilithic on rocks beneath evergreen broad-leaved forests or bamboo forests, 111°46′56"E, 22°17′30"N, elev. 216 m, 18 May 2021, She-Lang Jin, Bin Chen, Yi Huang & Xiao-Sa Huang JSL8008 (holotype: CSH 0149666 !; isotypes: CSH!, IBK!, KUN!, PE!)

Diagnosis:— Leptochilus tridigitatus is similar to L. poilanei in frond dimorphism and lamina division pattern, but differs by the lobes of fertile fronds elliptic-lanceolate to narrowly elliptic-lanceolate (vs. linear in the latter), 4–22 mm (vs. 1.5–3 mm) wide and with obtuse (vs. acuminate) apex.

Description: Plants perennial, evergreen, lithophytic. Rhizome 1.5–2.7 mm in diam., dorsiventrally flattened, apex covered with many scales; scales ovate-lanceolate, with expanded base, 3–4 × 0.8–1.3 mm, brown to grayish brown, peltate, clathrate, abaxially with a tuft of stiff brown hairs at insertion position, margins obtusely toothed. Fronds dimorphic, distant; fertile fronds longer, often 2× as long as sterile ones. Sterile fronds: 9–18(–21) cm long; stipe stramineous, 0–8 cm long, 0.5–0.9 mm in diam. near middle. with a few ovate-lanceolate scales at base, upward smooth and glabrous, shallowly grooved adaxially; lamina simple or trifid, sometimes 1 lateral lobe absent, occasionally pinnatifid and with 2 pairs of lateral lobes, papery, green adaxially, light green abaxially, glabrous on both surfaces, simple lamina lanceolate or oblong-lanceolate, 5–12 × 1.5–3 cm, broadest near middle, base cuneate and decurrent more or less, with narrow wings along all or upper part of stipe, margins entire or slightly repand; lateral lobes elliptic, broadest at middle, narrowed toward base, acute or subacute at apex, 2–5 × 1–2 cm, basiscopic base decurrent into narrow wing along rachis or upper stipe, midribs stramineous; apical lobe similar to lateral ones but larger, broadest at or below middle, 4–9 × 1.6–3.7 cm; lateral veins more or less straight or zigzag and dichotomous distally, forming 2 or 4 irregularly arranged areoles, invisible, veinlets anadromous, thinner than lateral veins, included veinlets simple or forked. Fertile fronds: 24–44 cm long; stipe stramineous, 10–30 cm long, 0.6–1.1 mm in diam. near middle. with a few scales at base, smooth and glabrous above base, shallowly grooved adaxially; lamina simple or tripartite, sometimes 1 lateral lobe absent, occasionally pinnatifid and with 2 pairs of lateral lobes, papery or thinly papery, green adaxially, light green abaxially, glabrous on both surface, simple lamina elliptic-lanceolate or narrowly elliptic-lanceolate, 9–12 × 0.8–1.5 cm, broadest at or below middle, acuminate at apex, base narrowly cuneate and decurrent more or less, margin entire or slightly repand; lateral lobes narrowly elliptic-lanceolate, broadest at middle, acuminate at apex, 2.5–9 × 0.4–1.7 cm, basiscopic base decurrent to narrow wing along rachis or upper stipe, midribs stramineous; apical lobe similar to lateral ones but larger, broadest at or below middle, 8–13 × 0.9–2.2 cm; lateral veins more or less zigzag and ill defined, dichotomous distally, forming 2 or 3 irregularly arranged areoles, slightly visible, included veinlets usually simple. Sori long linear, sometimes interrupted, touching midrib, at an angle of 5°–30° with midrib, lower parts of sori often J-shaped; paraphyses absent. Spores 64 per sporangium.

Geographical distribution and Ecology:— Leptochilus tridigitatus was found in Guangdong Province and the Hong Kong Special Administrative Region, South China ( Fig. 4 ). It may be distributed to Hainan Province. Most of the individuals of L. tridigitatus were observed to be epilithic on rocks beneath evergreen broad-leaved forests, bamboo forests or bamboo and broad-leaved tree mixed forests. Some individuals occasionally can extend their rhizomes to parts of the rocks covered with soil or to lower portion of tree trunks.

Etymology: —The epithet of Leptochilus tridigitatus is derived from the Latin “ tridigitatus ,” meaning “threefingered,” referring to the shape of the fronds.

Chinese name:— 三Dzäǟ (sān zhǐ xiàn jué)

Additional specimens examined: —Guangdong: PE01049429, PE01049415, PE01049564, NAS00070019, PE01923034, SZG00033765, SZG00034331, SZG00034334, IBSC0916965; Hong Kong: IBSC0685980, IBSC0685981.

Figures

FIGURE 2. Leptochilus tridigitatus H.J. Wei.—A. Habitat.—B. Habit.—C. Rhizome with sterile fronds and lower portions of stipes of fertile fronds.—D. Adaxial view of sterile frond.—E. Abaxial view of fertile lamina.—F. Portion of apical lobe of fertile frond.—G. Rhizome scale.

FIGURE 3. Leptochilus tridigitatus H.J. Wei.—A. Habit.—B. Portion of sterile lamina showing venation.—B. Portion of apical lobe of fertile frond showing venation and sori.

FIGURE 4. Geographical distributions of Leptochilus tridigitatus (red rings) and L. poilanei (green ring).