Diplazium clivicolum H. J. Wei & Z. Y. Zuo, 2025

Wei, Hong-Jin & Zuo, Zheng-Yu, 2025, Diplazium clivicolum (Polypodiales, Athyriaceae), a new fern species from southern Yunnan, China, PhytoKeys 261, pp. 125-134 : 125-134

Diplazium clivicolum H. J. Wei & Z. Y. Zuo sp. nov.

Figs 3 , 4

Type.

China • Yunnan: Mengla County, Yaoqu Yao Ethnic Town, Sharen Village , on slope in evergreen broad-leaved forest, 21°48'N, 101°35'E, elev. 930 m, 31 July 2024, She-Lang Jin & Zheng-Yu Zuo JSL 9679 (holotype: CSH 0197777 !; isotypes: CSH!, IBK!, KUN!, PE!) .

Diagnosis.

Diplazium clivicolum morphologically resembles D. incomptum in terms of rhizome type, lamina division, serration of lobe edge, venation pattern and sori position and shape, but differs by having broader lamina, contracted lamina apex, asymmetric pinna base, oblong-obovate and sometimes imbricate lobes and longer sori.

Description.

Plants evergreen, medium-sized. Rhizome ascending to erect, with dense, black-brown, stiff, fleshy, long, thick roots, apex densely scaly; scales brown or dark brown, lanceolate, seldom broadly lanceolate, 5–8 × 1–2 mm, membranous, margins slightly denticulate or nearly entire, with narrow, fragmented black edges. Fronds caespitose, 86–106 cm; stipe (37 –) 43–53 cm, 3.5–6 mm in diam. at base, 2–3 mm in diam. near middle, base black-brown, densely covered with scales similar to those on rhizome, above base stramineous, sparsely covered with adpressed, lanceolate scales, upwards stramineous, subglabrous, shallowly grooved adaxially; lamina pinnate-pinnatipartite or pinnate-pinnatisect near base, ovate, 45–54 × 38–51 cm, apex somewhat abruptly narrowed and elongated acute; pinnae 9–10 pairs, lower pairs 16–26 × 3–4.3 cm, broadest at middle or below, slightly narrowed towards base, alternate or subopposite, ascending, lanceolate, stalked, pinnatilobate to pinnatifid, base asymmetrical with basal adaxial and abaxial lobes alternate, apex long acuminate; basal pair of pinnae slightly shortened, pinnatipartite, 16–20 cm, with stalk 4–11 mm; second pair of pinnae pinnatipartite or pinnatisect to costa, 20–26 cm, with stalk 3.5–7 mm, upper pinnae gradually reduced below cuspidate apex; pinna lobes often up to 12 pairs, ascending, approximate, contiguous or imbricate, oblong to oblong-obovate, 12–25 × 7–11 mm, base often narrowed and cuneate when lamina fully developed, adnate to narrow wings, margins notched, repand, repand-toothed or crenate, apex rounded or rounded-truncate, basal pair of pinna lobes on lower pinnae anadromous, often abruptly reduced, sometimes completely free, narrowly or broadly adnate; veins pinnate, prominent abaxially, visible adaxially, veinlets 5–7 pairs, oblique, simple, seldom forked. Lamina thickly herbaceous or papery when dry, green adaxially, yellow-green abaxially, glabrous on both surfaces; rachis and costae stramineous, adaxially shallowly grooved, with abundant squarrose-glandular papillae in grooves, abaxially subglabrous along rachis and with sparse brown long appressed articulate hairs along costae. Sori linear, medial, often up to 9 mm, seldom up to 10 mm, 5–7 pairs per lobe, single or double on acroscopic basal veinlet, oblique, from near mid-rib to near margin; indusia brown, linear, membranous, entire, persistent. Spores light brown, reniform to phaseoliform, 22–32 μm in polar axis, 40–56 μm in equatorial axis, perispore with a few long and low folds, forming a rugate surface, 64 per sporangium.

Notes.

Characterised by the decumbent or erect rhizome bearing scales, pinnate-pinnatipartite fronds, alternate pinnae with stalks, but lacking auricles at the acroscopic bases, free veins and sori longer than two-thirds the length of the veins. Diplazium clivicolum should be classified as a member of section Anisogonium on the basis of the key descriptions of Wei et al. (2025) and supported by our phylogenetic analysis.

Geographical distribution.

Currently only found at the type locality, belonging to Xishuangbanna National Nature Reserve (Fig. 5 ).

Ecology and conservation assessment.

One population of approximately 30–50 individuals was discovered on a hillside within an evergreen broad-leaved forest, at an elevation of roughly 910– 930 m. However, this habitat is just located at the Reserve boundary adjacent to an extensive farmland and close to a village, placing it at ongoing risk of destruction. In accordance with IUCN Criteria ( IUCN 2012), the new species is temporarily classified as critically endangered. Given the abundance of similar ecological niches in this area, it is hoped future surveys will reveal more habitat locations.

Etymology.

The specific name is derived from the Latin term “ clivicolum ”, which means “ dwelling on a slope or hillside ”, referring to its habitat.

Chinese name.

坡生短肠蕨 (pō shēng duǎn cháng jué)

Paratypes.

Same place as the holotype, 31 Jul 2024 Zheng-Yu Zuo Zuo 6433 ( KUN!) · ibid., 31 Oct 2024, She-Lang Jin, Zheng-Yu Zuo & Rui Zhang JSL 10125 ( CSH!) · ibid., Zheng-Yu Zuo Zuo 7161 ( KUN!)

Figures

Figure 3. Diplazium clivicolum. A. Habitat; B. Habit; C. Adaxial view of portion of pinna; D. Abaxial view of portion of pinnae; E. Portion above base of stipe; F. Adaxial view of lower portion of pinna stalk with portion of rachis; G. Rhizome with lower portion of stipes; H. Scales from stipe base (left and middle) and 2 cm-tall fiddlehead (right); I. Stipe base exhibiting scales. Photographed by Hong-Jin Wei.

Figure 4. Diplazium clivicolum. A. Habit; B. Portion of pinna showing veins and sori. Illustrated by Hong-Jin Wei.

Figure 5. Geographical distributions of Diplazium clivicolum (center of rings) in Yunnan Province, China.