Asplenium danxiaense K.W.Xu, 2022

Xu, Ke-Wang, Lin, Chen-Xue, Guo, Jian-Qiang, Zhou, Xin-Xin, Liao, Wen-Bo & Mao, Ling-Feng, 2022, Asplenium danxiaense sp. nov. (Aspleniaceae, Aspleniineae), a new tetraploid fern species from Guangdong, China, based on morphological and molecular data, European Journal of Taxonomy 798, pp. 162-173 : 165-169

Asplenium danxiaense K.W.Xu sp. nov.

urn:lsid:ipni.org:names:77260762-1

Figs 3A, E , 4 , 5A–B

Diagnosis

Asplenium danxiaense K.W.Xu sp. nov. somewhat resembles A. coenobiale and A. pulcherrimum by its dark brown to black rhizome scale with fimbriate to subentire margin, shiny dark brown to black, rigid and threadlike stipe and rachis, finely dissected frond, and lophate (cristate-alate) perispore, but the former has rhizome scales narrowly triangular to lanceolate, with a short apical tail, basal-most basiscopic secondary pinnae usually largest, fertile segment scarce, and exospore length usually more than 50 μm. In contrast, A. coenobiale and A. pulcherrimum have scales narrowly triangular to linearsubulate, with a long apical tail, basal acroscopic pinnule usually largest, fertile segment abundant, and exospore length usually less than 50 μm.

Etymology

Based on the mountain name, Danxia, in northern Guangdong, China, and the Latin suffix, - ense, of origin, referring to the type locality of the species.

Type material

Type CHINA • Guangdong province, Shaoguan City, Renhua County, Danxia mountain ; 25°01′41.076″ N, 113°41′44.982″ E; elev. 150 m; in evergreen broad-leaved forest in a cave of Danxia landform; 12 May 2021; Jian-Qiang Guo & Xin-Xin Zhou XKW674; holotype: NF!; isotype: SYS !.

Description

Plants up to 30 cm tall. Rhizome erect, apex scaly; scales dark brown to black, narrowly triangular to lanceolate, (2.5–)4–5 × 0.4–0.9 cm, clathrate, margin fimbriate to subentire, apex shortly hairpointed. Fronds caespitose; stipe shiny, purplish black, 10–16(–20) cm, terete, rigid and threadlike, subglabrous; rachis shiny purplish black, becoming green in upper half toward apex, sulcate adaxially, subglabrous; lamina firmly herbaceous, green, subglabrous, triangular to ovate-triangular, 8–12 × 4–7 cm, base truncate, (2 or) 3-pinnate, apex acuminate; primary pinnae in (6–) 8–14 pairs, subopposite to alternate, overlapping, stalk short, purplish black to green abaxially, basal pinnae largest, ovatelanceolate, 3–6 × 1.5–2 cm, base obliquely truncate to truncate, apex subacute; secondary pinnae in 3–7 pairs, anadromous, basal basiscopic secondary pinnae usually largest, triangular-ovate, 0.7–1.5 × 0.5–0.8 cm, stalk short to subsessile, base asymmetrical, acroscopic side truncate, basiscopic side cuneate, apex obtuse; ultimate segments 2–4 pairs, ovate-oblong to linear, apex with 2–4 short and broadly triangular, obtuse to submucronate or sharp teeth. Costa and costules sulcate adaxially, green, veins slightly raised or flat adaxially, anadromous, 1 vein per segment, not reaching margin. Sori 1 per fertile, forked and pouch-shaped segment, medial to subterminal on acroscopic veinlet, oval to linear, 1–3 mm long; indusium grayish green, oval to linear, membranous, margin nearly entire, persistent, opening toward costules, persistent. Spores brown to dark brown, exospore 52–60 μm long, lophate (cristate-alate) perispore.

Additional material

CHINA • Guangdong province, Shaoguan City, Renhua County, Danxia mountain ; 25°01′41.076″ N, 113°41′44.982″ E; elev. 150 m; in evergreen broad-leaved forest in a cave of Danxia landform; 12 May 2021; Jian-Qiang Guo & Xin-Xin Zhou XKW675; NF!.

Distribution and habitat

Asplenium danxiaense sp. nov. is only known from Guangdong, China, growing in a cave of Danxia mountain in evergreen broad-leaved forest, at the elevation of 100– 300 m.

Vernacular name

We propose a Chinese name, Dānxiáshān tiějiǎojué (丹DZƜŨffldz) to reflect the type locality of the new species.

Conservation Status

We provisionally assess Asplenium danxiaense sp. nov. as Critically Endangered based on criterion D of IUCN (2012). Only one population and fewer than 50 individuals of A. danxiaense sp. nov. are known from Danxia mountain. It was not seen by one of us during separate expeditions to nearby sites on Danxia mountain.

Figures

Fig. 3. Scalemorphology ofthe newspecies andits affinities.A, E. AspleniumdanxiaenseK.W.Xu sp. nov. B, F. A. pulcherrimum (Baker) Ching ex Tardieu. C, G. A. coenobiale Hance. D, H. A. cornutissimum X.C.Zhang & R.H.Jiang.

Fig. 4. Asplenium danxiaense K.W.Xu sp. nov. A. Danxia landform in the type locality of the new species. B. Habitat of the new species in a cave. C. Habit. D. Abaxial view of lamina. E. Abaxial view of lamina apex. F. Adaxial view of lamina. E. Rhizome and root.

Fig. 5. Spores of the new species Asplenium danxiaense K.W.Xu sp. nov. and its affinities. A, B. A. danxiaense K.W.Xu sp. nov. C. A. cornutissimum X.C.Zhang & R.H.Jiang. D. A. coenobiale Hance. E. A. pulcherrimum.(Baker) Ching ex Tardieu.