Tectaria chinensis (Ching & Chu H. Wang) Christenhusz (2010: 58)

Dong, Shi-Yong, Tan, Shi-Shi, Pham, Van The & Phan, Ke Loc, 2018, The true Tectaria chinensis (Tectariaceae): morphology, distribution, and allied species, Phytotaxa 376 (1), pp. 60-67 : 61-64

Tectaria chinensis (Ching & Chu H. Wang) Christenhusz (2010: 58) . Fig. 1 , 2 .

Basionym:— Ctenitopsis chinensis Ching & Chu H. Wang (1981: 124) .

Type:— CHINA. Yunnan: Hekou, in 1955, elev. 100 m, Department of Biology, Yunnan University ( DBYU) 512 (holotype PE!)

Caudex erect, usually 15–40 cm long, 1–2 cm thick. Stipe 40–60 cm long, stramineous or dark brown, minutely hairy and scaly throughout, scales lanceolate, 7–8 × 1.2–1.5 mm at base, rather copious, becoming smaller and fewer to rachis, dark brown or light castaneous. Fronds more or less dimorphic, with fertile laminae little contracted and smaller than sterile ones, lamina ovate, 25 × 20 to 85 × 50 cm, 2- to 3-pinnatifid, round at base, terminal part pinnatifid and acute at apex; free pinnae 2–5 (6) pairs, opposite or nearly so, deeply lobed to costae or 1-pinnate at base, basal pinnae the largest, 14 × 6 to 35 × 22 cm, ovate or triangular, broadest at base, with stalks 0.5–3.5 cm long, pinnatifid and acute toward apex, upper pinnae narrowly triangular or oblong, 12 × 3 to 25 × 17 cm, deeply lobed to the wing of costae; free pinnules 0–2 pairs, falcate, lobed halfway or more deeper to costules, the basal basiscopic one on basal pinna the largest, 8 × 2 to 18 × 6 cm, sessile or nearly so, basiscopic pinnules much longer than acroscopic ones on basal pinna, ultimate lobes entire, acute at apex. Veins anastomosing along costae and costules, forming a row of areoles on either side of costae and costules, additional areoles few, no free veinlets included in areoles, veins outside costular areoles free; adaxial surface more densely hairy on midribs of pinnae, no hairs present on abaxial surface except those on costae and costules. Sori round or rarely slightly elongated, separate, less than 1 mm in diam., dorsal on anastomosing veins or free veins near margin of lamina, mostly in two rows between lateral veins in ultimate lobes, exindusiate.

Distribution: —Restricted to southern China and northern Vietnam. In China: southern Yunnan (Hekou, Jinping, Lüchun, Mengla, and Xichou); in Vietnam: Ha Giang (Cao Bo, Vi Xuyen Distr.), Lao Cai (Nam Xe, Van Ban Distr.). This is the first time to confirm T. chinensis in Vietnam. It is also highly expected to find this species in northern Laos.

Habitat: —Terrestrial, on slope beside stream in closed forest in valley, elev. 120–1250 m.

Additional specimens examined: — CHINA. Yunnan: Hekou ( Nanxi ), 27 March 1987, W. M. Chu et al. 21939 ( PYU!) ; Jinping ( Ma’andi ), 103°29 ′ 19 ″ E, 22°46 ′ 38 ″ N, 30 Oct 2017, S. Y. Dong 4789 ( IBSC!) ; Lüchun ( Qimaba ), 22°49 ′ 12 ″ N, 102°15 ′ 15 ″ E, 28 Oct 2015, S. Y. Dong 4343 ( IBSC!) ; Mengla ( Mengla Town ), 21°36 ′ N, 101°35 ′ E, Mar

2000, B.G. Li 0908247 (HITBC!); ibid., 21°35 ′ N, 101°34 ′ E, 23 Oct 2015, S. Y. Dong 4291, 4310 & 4312 ( IBSC!) ; ibid., 21°36 ′ N, 101°33 ′ E, 24 Oct 2015, S. Y. Dong 4335 ( IBSC!) ; Xichou (Bolin), 18–19 March 1987, W. M. Chu et al. 21809 & 21811 ( PYU!) .

VIETNAM. Ha Giang: Tham Ve Village nearby, Cao Bo, Vi Xuyen Distr., 22°44 ′ 36 ″ N, 104°54 ′ 09 ″ E, 19 Nov 2017, S.Y. Dong 4855 (HNU!, IBSC!). Lao Cai: Nam Si Tan Village, Nam Xe, Van Ban Distr., 22°02 ′ 31–57 ″ N, 103°58 ′ 32-35 ″ E, 26 Feb 2001, D.K. Harder et al. 6911 (HN!).

Note: —The type of Tectaria chinensis, DBYU 512 (PE), is actually an incomplete frond that consists of a broken stipe and a lamina without basal pinnae ( Fig. 1 ). The lowest pinnae seen on the sheet of type specimen was mistakenly regarded as the basal pinnae by Ching & Wang (1981), which leaded them and later authors ( Wang 1999, Cheng 2005, Xing et al. 2013) to associate this species with Ctenitopsis subsageniacea sensu Ching (1938: 311) [= T. austrosinensis (Christ 1907: 145) C. Christensen (1934: 177) ( Dong 2017)], a species with the basal basiscopic lobes reduced on basal pinnae. Based on the misinterpretation of T. chinensis , we had never associated our new collections featured by long-erect caudices with T. chinensis because in the new collections the basal basiscopic pinnules of basal pinnae are constantly produced ( Fig. 2 ). On the other hand, of all known species in Tectaria from China T. chinensis is the only dubious species which is poorly presented in herbarium; this fact reminded us to connect our new collections featured by remarkable long caudex with T. chinensis . The overall similarity, especially the consistent venation and sori positions between the new collections and the type of T. chinensis makes it sure that our new collections are just the individuals of T. chinensis . Now it is clear that T. chinensis is with the basal basiscopic pinnules being produced on basal pinnae and is not at all similar to T. austrosinensis .

Tectaria chinensis is very special by having remarkable caudices (up to 40 cm), which, as far as we know, was not observed or recorded for any other species in Tectaria . Based on our observations in the field and in herbaria, the rhizome in Tectaria can be determined as two basic states, erect and creeping ( Ding et al. 2014). For the erect state, the rhizome measures generally 2–3 cm tall or rarely to c. 8 cm; in the latter cases, the erect rhizome is as thick as c. 5 cm in diameter and mainly consists of the remained, crowded stipe-bases of old fronds in many years. The caudex, however, occurring in T. chinensis is a different state which is not very thick and apparently long, measuring 1–2 cm in diameter and 15–40 cm tall. As mentioned above, the long, erect caudex is not occasional in T. chinensis ; it stably occurs in all seven populations we have met in the field. As the seven populations all were found in closed forest where the light is poor, we suppose that the erect caudex of T. chinensis might be a habitat adaptation which allows the plant to get more sunlight in the deep shade of rainforest in valley.

Besides the long, erect caudex, the combination of the partly free venation and the vein-dorsal sori position in T. chinensis is also very rare. Tectaria chinensis is the sole species in Tectaria from China and Vietnam which is featured by the veins forming costal and costular areoles (lacking free included veinlets) combined with sori dorsal on anastomosing veins (as well dorsal on free veins). In the whole range of Indochina, there are only two species, T. chattagramica ( Clarke 1880: 548) Ching (1931: 35) and T. tenerifrons ( Hooker 1864: 104) Ching (1931: 34) , possessing the similar venation and the sori feature as in T. chinensis . Evidently T. chinensis is very different from the two species in other characters, such as the long-erect caudex (short in T. chattagramica or long-creeping in T. tenerifrons ), copiously scaly stipe (glabrous in both T. chattagramica and T. tenerifrons ), and dark brown stipe and rachis (polished and castaneous in T. chattagramica or light stramineous in T. tenerifrons ). These two species ( T. chattagramica and T. tenerifrons ) have not been recorded in either China or Vietnam. The former is distributed mainly in northeastern India and nearby regions ( Tagawa & Iwatsuki 1988), with one collection so far known from northern Thailand (Hansen et al. 11254 at K!); and T. tenerifrons is known in northern and southwestern Thailand, southern Burma, and Laos ( Tagawa & Iwatsuki 1988, Lindsay & Middleton 2012). As for the sympatric species which share similar lamina division and venation with T. chinensis , such as T. coadunata , T. devexa ( Kunze 1848: 259) Copeland (1907: 415) , T. multicaudata , and T. remotipinna Ching & C.H. Wang (1981: 129) , the sori in these species are mostly terminal on free veins (included in areoles or not) and are not dorsal on those forming costal and costular areoles as in T. chinensis . In addition, the sori are large and distinctly indusiate in these sympatric species, making the soriexindusiate T. chinensis very remarkable in Tectaria from China and Vietnam.

Morphologically T. chinensis is most close to T. multicaudata , both having the same pattern of lamina division, the similar venation (veins forming costal and costular areoles), and with copious scales throughout stipe. However, molecular evidence did not support the very close relationship between T. chinensis and T. multicaudata . In the phylogenetic tree based on five plastid regions ( Fig. 1 in Dong et al. 2018), T. multicaudata was placed on the base of one of two subclades in Clade III ( Ctenitopsis group), being sister to the remaining species including T. austrosinensis and T. chinensis ; while T. chinensis (then labelled as T. sp. 4) was supported as sister to the T. fuscipes lineage which includes free-veined T. dissecta ( Forster 1786: 81) Lellinger (1968: 156) , T. setulosa ( Baker 1890: 265) Holttum (1988: 479) , and an undescribed species (labelled as T. sp. 1). Tectaria chinensis seems to be an isolated species in Tectaria and so far the close affinity of T. chinensis has not been found.

Figures

FIGURE 1. Holotype of Tectaria chinensis (Ching & Chu H. Wang) Christenh (DBYU 512 at PE), an incomplete frond with the basal pinnae missing.

FIGURE 2. Tectaria chinensis (Ching & Chu H. Wang) Christenh. A & B, habit. C, two long, erect caudices. D, scales on lower stipe. E, part of fragment on upper lamina, showing veins forming costal areoles and sori on anastomosing veins or dorsal on free veins. (A from Dong 4343 at IBSC, B–E from Dong 4789 at IBSC).