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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: 162-173, DOI: https://doi.org/10.5852/ejt.2022.798.1679, URL: http://dx.doi.org/10.5852/ejt.2022.798.1679

The Asplenium coenobiale complex is distributed in Eastern Asia and Southeast Asia with its distribution center in southwestern China. In this study, we carried out a detailed morphological, cytological, and phylogenetic study by adding two samples from Danxia landform in Guangdong. The sequences of five chloroplast markers and one nuclear marker of the A. coenobiale complex were analyzed with maximum likelihood and Bayesian inference, respectively. The morphological and phylogenetic analyses support the recognition of a new species (A. danxiaense K.W.Xu sp. nov.) of the A. coenobiale complex from a cave of Danxia mountain, Guangdong province, southern China. This new species can be distinguished from A. coenobiale and A. pulcherrimum by having scales narrowly triangular to lanceolate, apex ending in a short apical tail, basal basiscopic pinnule usually largest, fertile segment scarce, and exospore length usually more than 50 μm and shows significant molecular differences from other species in this complex. A detailed description and illustrations are presented.

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 ��m. 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 ��m. 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 ��m 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, Dānxi��shān tiěji��oju�� (���DZ��Ũffldz) 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., Published as part of 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, pp. 162-173 in European Journal of Taxonomy 798 on pages 165-169, DOI: 10.5852/ejt.2022.798.1679, http://zenodo.org/record/6341216, {"references":["IUCN. 2012. IUCN Red List Categories and Criteria: Version 3.1. Second edition. Gland, Switzerland. Available from https: // portals. iucn. org / library / node / 10315 [accessed 5 November 2021]."]}