Asplenium subcrenatum Ching ex S.H.Wu, Bull. Bot. Res. 9(2): 86, f. 5. 1989.

Xu, Ke-Wang, Wang, Lu-Lu & Zhang, Li-Bing, 2021, Taxonomic revision of the Asplenium wrightii complex (Aspleniaceae) with reinstatement of A. alatulum and A. subcrenatum, PhytoKeys 172, pp. 75-91 : 75

Asplenium subcrenatum Ching ex S.H.Wu, Bull. Bot. Res. 9(2): 86, f. 5. 1989.

Type.

China. Yunnan: Malipo, Chung-dzai, in mixed forest, elev. 1600-1800 m, 3 Nov 1947, K.M.Feng 12803 (holotype: PE (PE00059494 [image!])). Fig. 3B .

Description.

Plants up to 30-55(-70) cm tall. Rhizomes erect to decumbent, densely scaly; scales reddish-brown, narrowly triangular, 4-8 × 0.7-1.1 mm, margin near entire (Figs 5E , 2B, E, H ). Fronds tufted; stipe stramineous-green or reddish-brown, (10-)15-20(-25) cm, base densely scaly, scales reddish-brown, fibrillose or similar to those on rhizome; lamina oblong-lanceolate, (12-)15-40(-50) × (5-)8-15(-17) cm, base truncate, apex acute, 1-pinnate; pinnae (15-)18-25(-30) pairs, basal pinnae subopposite, others alternate, at an angle of ca. 60°-80° to rachis, with stalks (1-)2-3 mm, lower pinnae slightly reduced, suprabasal pinnae falcate-lanceolate, (3-)6-10 × (0.6-)1-1.5 cm, base asymmetrical, acroscopic side truncate at an angle of (40°-)45°-60(-70°) to costa, basiscopic side cuneate, becoming decurrent on rachis in apical part of lamina, margin almost entire to crenate-sinuate, apex acuminate (Fig. 5B, C, D ). Veins (1 or)2-forked, with terminal hydathode. Fronds papery, dark green when dry, subglabrous; rachis reddish-brown to stramineous-green, densely scaly to subglabrous, scales similar to those on stipe, terete abaxially, winged towards apex. Sori linear, (2-)3-8(-10) mm, usually on acroscopic veinlets, medial (Fig. 5C ); indusia greyish-brown to dark brown, linear, papery, margin entire, opening towards costa, persistent. Spores with average exospore length 40-45 μm, perispore cristato-alate.

Distribution and habitat.

Asplenium subcrenatum is distributed in China and Vietnam. It grows as an epiphyte on tree trunks or occurs on rocks by stream-sides in the evergreen broad-leaved forests of limestone areas (Fig. 5A ).

Additional specimens examined.

China. Gauangxi: Jingxi County, Xinjing Village, Bahong, 23°07'05.56"N, 106°30'24.53"E, 31 Oct 2010, L.B.Zhang, H.He & Y.Wang 5492 (MO!); Nandan County, Mangchang Village, Lala, 25°10'24.92"N, 107°23'16.26"E, 12 Oct 2010, L.B.Zhang, H.He & Y.Wang 5492 (MO!); Guizhou: Libo County, Jialiang Village, 18 Oct 2018, JSL6678 (CSH!); Libo County, Shuili Xiang, Shangshuizan, on a dry mountain with mixed pine and broad-leaved forest, 25°28'46"N, 107°47'47"E, 8 Jun 2016, L.B.Zhang et al.9193 (MO!); Libo County, Wong’ang, Dongduo, elev. 780 m, 16 Sep 2007, L.B.Zhang 472 (MO!); Guiding County, Houchangbao Xiang, on cliffs by a stream, elev. 1100 m, 26°14'47"N, 107°12'37"E, 10 Jun 2016, L.B.Zhang, Y.F.Duan, N.T.Lu & X.Y.Miao 9250 (MO!); Yunnan: Xichou County, Fadou Village, Xinjing, elev. 1800 m, 10 Jun 2013, Y.H.Yan YN250 (CSH-0046594!); the same locality, 9 Jan 1962, S.G.Wu4222-62 (PE-00912376!); Malipo County, elev. 1100 m, 21 Jan 1940, C.W.Wang 86341 (PE-00912378!); Xiajinchang Village, Huangjinyin, elev. 1416 m, 22°07'28.89"N, 104°51'11.15"E, 29 Oct 2015, Fan 13883 (SYS!); the same locality, 29 Oct 2015, Fan 13884 (SYS!); the same locality, 11 Dec 2015, the same locality, Xu TTJ-YN-031 (SYS!); 11 Dec 2015, Xu TTJ-YN-032 (SYS!); Tianbao County, Tianbao Village, Bajiaoping, elev. 1135 m, 22°58.6607'N, 104°50.8035'E, 30 Oct 2015, Fan 13884 (SYS!); Maguan County, Bazhai, Lvditang, 7 Apr 2017, X.C.Zhang et al. 8219 (PE-02236348).

Vietnam. Ha Giang: Yen Minh District, Lao Va Chai Municipality, vicinities of Chi Sang Village, elev. 1450 m, 23°06'20"N, 105°04'25"E, 09 Dec 2005, Averyanov, Leonid V. HAL8420 (MO-3136047!); Vi Xuyen District, Tung Ba Community, Khau Ca Nature Reserve, Hom Mountain, elev. 900 m, 13 Dec 2013, L.B.Zhang, L.Zhang & L.T.Ngan 6966 (MO!); Quan Ba District, Nghia Thuan Community, Bat Dai Son Nature Reserve, 10 Dec 2013, L.B.Zhang, L.Zhang & L.T.Ngan 6882 (MO!).

Note.

Just like Asplenium alatulum , a comprehensive taxonomic study of A. subcrenatum was scarce after this species was described. Lin and Viane (2013) treated it as a synonym of A. wrightii , based only on macromorphological data. Both our molecular data ( Xu et al. 2020) and micromorphological data in this study (Figs 1 , 2 ) support the distinction of A. subcrenatum .

Asplenium subcrenatum is different from A. wrightii in having its stipe and rachis covered with reddish-brown scales (Fig. 2B, E, H ) (vs. brown to dark brown scales, Fig. 2A, D, G ), scale margins nearly entire (vs. glandular margins or long-fibrillose) and pinna margins almost entire to crenate-sinuate (vs. serrate to coarsely dentate). Meanwhile, the perispores of A. subcrenatum are different from those of A. wrightii . The folds of A. subcrenatum are cristato-alate and areolofenestrate and the margins of the folds are echinulate, while the folds of A. wrightii are cristato-alate and imperforate and the margins of the folds are echinulate or approximately laevigate.

Geographically, Asplenium subcrenatum was only known from the type locality Malipo County and Yanshan County, southern Yunnan, China ( Wu 1999). Our study, based on specimen investigations and the field survey, shows that this species is mainly distributed in limestone areas of south-western China and northern Vietnam, while A. wrightii is widely distributed in acidic soils in southern China and Japan and it might occur in Korea.

Figures

Figure 1. Scanning electron micrographs of spore and stomata of A. alatulum, A. subcrenatum and A. wrightii A-F A. wrightii G-I A. subcrenatum J-L A. alatulum.

Figure 2. Scales of A. alatulum, A. subcrenatum and A. wrightii. A, D, G A. wrightii B, E, H A. subcrenatum C, F, I A. alatulum.

Figure 3. Type of Asplenium alatulum Ching (A barcode PE 00059412), A. subcrenatum Ching ex S. H. Wu (B barcode PE 00059494), A. wrightii Eaton ex Hooker (C barcode NY 00128031) and isotype of A. wrightii GH (D barcode GH 00020612).

Figure 5. Asplenium subcrenatum A Habitat and habit B Portion of lamina showing abaxial view of pinna C Abaxial view of pinna showing the serrate to coarsely dentate margin D Adaxial view of upper portion of lamina E Lower portion of stipes showing the reddish-brown scales.