Hymenasplenium obtusidentatum Y.Fen Chang & G.Cheng Zhang, 2022

Chang, Yanfen, Zhang, Guocheng, Wang, Zhixin & Cao, Limin, 2022, Molecular and morphological evidence reveals a new fern species of Hymenasplenium (Aspleniaceae) from south and southwestern China, PhytoKeys 211, pp. 93-106 : 93

Hymenasplenium obtusidentatum Y.Fen Chang & G.Cheng Zhang sp. nov.

Type.

China. Yunnan Province, Xishuangbanna, Menghai: Chang1258. 2019. (holotype, HITBC; isotype, KUN) (Figs 2 , 3 ) .

Description.

Plants 25-40 cm tall. Rhizomes long creeping, 2-4 mm in diameter, apex scaly; scales brown, lanceolate to triangular, entire. Fronds remote, up to 6 mm apart, grayish green when dry, herbaceous; stipe reddish brown to dark brown, 10-20 cm long, base ca. 1-1.5 mm in diam., subglabrous, base with sparse scales similar to those on rhizome; lamina one-pinnate, narrowly triangular to triangular, 15-30 × 8-15 cm, base truncate and reduced, apex acuminate to caudate; rachis reddish brown to dark brown, subglabrous; pinnae 15-21 pairs, trapeziform to falcate, basal pinnae nearly opposite, middle pinnae 3.5-8 × 1-1.8 cm, dimidiate, apex obtuse to acute, base asymmetrical, acroscopic side truncate and often almost parallel to rachis, basiscopic side of basal pinnae excavate, in middle pinnae narrowly cuneate and entire, acroscopic margin serrate, teeth blunt or rounded; pinnae spreading to ascending. Veins forking and terminating in marginal teeth, basiscopic side with 4-6 veins lacking. Sori inframedial to medial, linear, 3-5 mm, indusia persistent, pale brown, membranous, entire, opening toward the costa. Spores elliptic to reniform, perispore fimbriate-alate, 38-43 μm in diam.; 64 spores per sporangium.

Diagnosis.

Hymenasplenium obtusidentatum is similar to H. excisum . However, H. obtusidentatum has a thinner rhizome and stipe, not shiny and reddish brown to dark brown stipe and rachis, blunt or rounded pinna marginal teeth, and truncate lamina base.

Distribution and habitat.

Hymenasplenium obtusidentatum is currently known to coexist with H. excisum in south and southwestern China, and adjacent areas. It occurs in soil or on rocks near streams in half-shaded forests at alt. 1000-1500 m.

Additional specimens examined.

China. Yunnan Province, Menghai County, 2019; Chang1256, Chang1260; Chang1261, Chang1262; Chang1339 (HITBC); Pu’er City, Pu’er Sun River National Forest Park , 2018; Xu 324 (SYS) . Hainan Province, Ledong County, 2019; Chang1284, Chang1285; Chang1286 (HITBC) .

Figures

Figure 2. Comparison of frond sketches of representative specimens available (H. obtusidentatum: Chang 1258, H. pseudobscurum: Chang 1010, H. excisum: Chang 992) for species of the Hymenasplenium excisum subclade.

Figure 3. Maximum likelihood phylogeny based on the concatenated plastid DNA sequence dataset. Maximum parsimony and Bayesian analyses recovered identical topologies with respect to the relationships among the main clades of the paleotropical Hymenasplenium. For each node, the following values are provided: maximum parsimony bootstrap (%) / maximum likelihood bootstrap (%) / and posterior confidence (p-value). Columns on the right refer to the subclades described in Xu et al. (2018 a). Outgroup taxa are shown as a sister to the paleotropical Hymenasplenium.