Arachniodes breviaristata H.J. Wei, 2023

Wei, Hong-Jin, Le, Xin-Gui & Chen, Bin, 2023, Arachniodes breviaristata (Dryopteridaceae): a new species from Jiangxi, China, Phytotaxa 629 (3), pp. 283-289 : 284-285

Arachniodes breviaristata H.J. Wei , sp. nov. ( Figs. 1 , 2 ).

Type:— CHINA. Jiangxi: Guixi City, Wenfang Town, Huangjinzhai Village , streamside, in forests, 117°21′E, 27°58′N, elev. 160 m, 25 May 2023, She-Lang Jin JSL9137 (holotype: CSH0166655 !; isotypes: CSH!, KUN!)

Diagnosis:— Arachniodes breviaristata resembles A. exilis ( Fig. 3 ), but differs by having ovate-triangular or triangular lamina with acuminate apex and basal basiscopic pinnule on lowest pinna shorter than or almost as long as adjacent one.

Description: Plants perennial, evergreen. Rhizome long creeping, ca. 4 mm in diam., densely clothed with scales; scales brown, blackish brown or dark brown, lanceolate, membranous, 6–9 × 1–1.8(–2.4) mm, margin entire, sometimes with several teeth at apex; roots slender, ca. 0.5 mm in diam.. Frond distant, 39–57 cm long. Stipe stramineous, 18–32 cm, ca. 1.5 mm in diam. at middle, narrowly grooved adaxially, base densely clothed with same scales as on rhizomes, upward scales becoming sparse and narrow, and with an enlarged base. Lamina ovate-triangular or triangular in outline, 21–29 × 15–21.5 cm, 2- or 3-pinnate, base round or broadly cuneate, gradually attenuate towards apex, apex acuminate. Lateral pinnae 7–8 pairs, oblong-lanceolate to broadly lanceolate, contiguous or imbricate, spreading or ascending, basal pair subopposite, others alternate, stalked, stalk 2–7 mm on lower ones; basalmost pinnae largest, occasionally as long as next ones, oblong-lanceolate to broadly lanceolate, 9.5–13 × 3.3–4.2 mm, base asymmetrical, acroscopically truncate, basiscopically broadly cuneate or rounded-cuneate, apex acuminate; primary pinnules ca. 16 pairs, alternate, obliquely oblong, rhombic-oblong or obliquely triangular-oblong, shortly stalked, imbricate, base acroscopically rounded-truncate, basiscopically cuneate or narrowly cuneate, apex acute or obtuse and mucronate, basal pair shorter than or as long as next pair, basiscopic one 12–22 × 7–11 mm, lower pairs pinnatifid to pinnatisect at base, with 1 or 2(–3) free lobes at base; lobes sessile, contiguous, orbicular-ovate or oval, margin serrate, aristate; distal pinnae gradually shortened, similar to basal pair, with basal basiscopic pinnule shorter than next one, and basal acroscopic pinnule as long as or slightly larger than next one. Lamina firm papery when dry, adaxially brownish green, glossy, abaxially yellowish green, with 1 or 2 microscales along veins; rachis and costae stramineous, shallowly grooved adaxially, covered with sparse scales; scales nearly subulate, 4–5.5 × 0.3–0.5, blackish brown or dark brown, base enlarged and toothed on margin, apex hairlike; veins pinnate, not reaching margin. Sori slightly nearer to costule, terminal on acroscopic veinlets; spores 64 per sporangium; indusium brown, membranous, orbicular-reniform, slightly erose at margin. Plants sexual diploid.

Geographical distribution: —The new species was only found in the type locality, Guixi City, Jiangxi Province, Southeast China ( Fig. 4 ).

Conservation Assessments and Ecology: —Only two small populations at a distance of approximately 200 m apart were found at the streamsides under a broad-leaved forest located just outside the edge of the Yangjifeng National Nature Reserve near a village. The number of individuals was difficult to count accurately because of their long creeping rhizomes. These two populations are facing the threat of extinction due to habitat loss. The new species is currently considered as critically endangered (CR C2a(i); D) according to the IUCN guidelines ( IUCN 2017). We believed that the new species is urgently needed for ex situ conservation. Three young individuals have been introduced into the Shanghai Chenshan Botanical Garden. We also plan to transplant some individuals to a relatively inaccessible area of the reserve to reduce the risk of extinction and look forward to the discovery of new populations in the reserve or in adjacent areas in future investigations.

Etymology: —The epithet of Arachniodes breviaristata is taken from the Latin prefix “brevi-,” meaning “short, brevis,” and “aristata ”, aristate, referring to short arista at the apex of serration.

Chinese name:— DZĉa叶Wĸ (duan mang fu ye er jue)

Additional specimens examined (paratypes):— The same place as the holotype, 9 June 2021, She-Lang Jin, Bin Chen, Si-Gang Li, et al. JSL8091 (CSH!); ibid., 25 May 2023, She-Lang Jin JSL9133 (CSH!).

Figures

FIGURE 1. Arachniodes breviaristata.—A. Habitat.—B, C. Habit.—D. Adaxial view of lower pinnae.—E. Abaxial view of lower pinnae.—F. Scales from stipe base (larger) and rachis (smaller).—G. Rhizome with lower portion of stipe (dried).

FIGURE 2. Arachniodes breviaristata.—A. Habit, based on paratype JSL8091.—B. Pinnule.

FIGURE 3. Arachniodes exilis.—A. Habitat.—B. Habit.—C. Adaxial view of portion of medial pinna.—D. Rhizome with lower portion of stipes.

FIGURE 4. Geographical distribution of Arachniodes breviaristata H.J. Wei (center of rings) in Jiangxi Province, China.