Leptochilus scandens H.J. Wei & Y. Huang, 2023

Wei, Hong-Jin, Huang, Yi & Chen, Bin, 2023, Leptochilus scandens (Polypodiaceae), a new microsoroid fern species from Guangdong, China, Phytotaxa 618 (1), pp. 79-85 : 80-83

Leptochilus scandens H.J. Wei & Y. Huang , sp. nov. ( Figs. 1 & 2 )

Type:— China. Guangdong: Yangchun City, Huatan Forest Farm, under evergreen broad-leaved forest beside a mountain streamlet, climbing on a tree stump, 111°44′E, 22°14′N, elev. 125 m, 18 May 2021, She-Lang Jin, Bin Chen, Yi Huang & Xiao-Sa Huang JSL8000 (holotype: CSH0193333 !; isotypes: CSH!, IBK!, KUN!, PE!) .

Diagnosis:— Leptochilus scandens is similar to L. ellipticus var. ellipticus , but differs by the fronds monomorphic (vs. subdimorphic in the latter) and lamina with at most 4 pairs (vs. 5–9 pairs) of lateral lobes which sometimes alternate (vs. usually opposite or subopposite).

Description: Plants initially generally epiphytic, then becoming hemiepiphytic ( Fig. 3 ), climbing up tree trunks, evergreen. Rhizome 2.5–3.5 mm in diam., dorsiventrally compressed, with 5–9 vascular bundles, apex with many scales, other part with sparse scales; scales peltate, lanceolate to ovate-lanceolate, 2.5–3.5 × 0.7–0.9 mm, dark brown, margins nearly entire, occasionally with 1 or 2 minute teeth. Frond monomorphic, distant, (14–)22–38(–47) cm long; stipe stramineous, (5–)13–24.5(–28.3) cm long, (0.6–) 0.9–1.3 mm in diam. at middle, with a few scales same as on rhizome at base, smooth and glabrous above base, shallowly grooved adaxially. Lamina ovate to broadly ovate, deeply pinnatifid, (8.7–)12.5–19(–21) × (5.5–)9.2–16.2(–18.7) cm, herbaceous to thinly papery, dull-green, glabrous, base broadly cuneate, becoming narrowly cuneate when near stipe and decurrent to stipe with narrow wings 1–3(– 5) cm long, margins entire to shallowly undulate-repand; lateral lobes 1–4 pairs, opposite to alternate, elliptic to elliptic-lanceolate, close to remote, broadest at middle, narrowed toward base, acute to shortly acuminate at apex, base decurrent, with narrow wing connecting with next lobe, lower 2 pairs usually same size, larger, (4.3–)7–11 × (0.7–)1.1– 1.8(–2.7) cm, midribs 2–4.5 cm apart, upper pairs slightly shortened and narrowed; apical lobe similar to lateral ones but larger, (6–)8–12(–15) × (1–)1.5–2.7(–3.2) cm; lateral veins rather tortuous, forming 2 or 3 irregularly arranged areoles, slightly visible, included veinlets simple or forked. Sori long linear, sometimes interrupted, paraphyses absent; spores 64 per sporangium.

Juvenile plant sometimes with simple or 2- or 3-lobed fertile fronds. Simple frond: stipe ca. 15 mm long; lamina narrowly elliptic-lanceolate, 18.5 cm long and 15 mm wide at middle, acuminate at apex, base decurrent nearly to base of stipe.

Geographical distribution: — Leptochilus scandens was found in the type locality in Yangchun city, Guangdong Province, South China ( Fig. 4 ) .

Conservation Assessments and Ecology: —Two populations with less than 10 mature individuals were found in disturbed areas near the city. One population is located in a forest farm (also a forest park), which is a temporarily protected area.All individual plants of this population climb on tree stumps, which limited the normal growth of the new species. This population could be threatened by human activities, even in the absence of logging. Unfortunately, some individuals photographed by the discoverer several years ago could not be found again during the survey. The other population is located at the margin of a forest landscape and occupies an area of 300–400 m 2 which is approximately 2.5 kilometers from a busy street. Most of the individuals were found growing on tree trunks or rocks. This population is likely to be threatened by urban expansion in the coming years and might disappear if the habitat is lost. The new species is currently considered as Critically Endangered (CR C2a(i); D) according to the IUCN guidelines ( IUCN 2019).

Etymology: —The epithet of Leptochilus scandens is taken from the Latin “ scandens ”, meaning “scandent, climbing”, referring to the scandent habit of the new species.

Chinese name:— ỆƟḦB (pan yuan xian jue)

Additional specimens examined (paratypes): — China. Guangdong: Yangchun City, Yunlingshan Mount , on rocks or tree trucks, 21 May 2021, She-Lang Jin, Bin Chen, Yi Huang & Xiao-Sa Huang JSL8051 ( CSH!, IBK!, KUN!, PE!) & JSL8051 A ( CSH!) .

Figures

FIGURE 1. Leptochilus scandens H.J. Wei & Y. Huang.—A. Habitat.—B. Some individual plants climbing on a tree trunk.—C.Adaxial view of frond.—D. Abaxial view of lamina with portion of stipe.—E.Abaxial view of fertile frond of juvenile plant.—F. Precocious plant with a precociously fertile simple fronds.—G. Scales from rhizome.—H. Portion of sterile lobe showing venation.—I. Dorsal sides of rhizomes with lower portions of stipes.—J. Ventral side of rhizome with lower portion of frond.

FIGURE 2. Leptochilus scandens.—A. Habit.—B. Pinna showing venation and sori.

FIGURE 3. Habit of Leptochilus scandens (C & D photographed by Xiao-Sa Huang).—A.Young individuals in epiphytic growth phase.— B. Hemiepiphytic individual.—C. Portion of adventitious roots of adult plants.—D. Lower portion of adventitious roots down to ground.

FIGURE 4. Geographical distributions of Leptochilus scandens (centers of rings) in Guangdong Province, China.