Aspidistra tenuistyla Aver., C.H.Nguyen & K.S.Nguyen, 2024

Chu, Quan Ngoc, Nguyen, Cuong Huu, Averyanov, Leonid V., Dai, Hai Vo, Nguyen, Khang Sinh, Maisak, Tatiana V. & Krupkina, Ludmila I., 2024, Aspidistra tenuistyla and A. luteo-rubra (Asparagaceae, Convallarioideae), a new tubuliflorous species from northern Vietnam, Phytotaxa 662 (2), pp. 161-169 : 162-168

Aspidistra tenuistyla Aver., C.H.Nguyen & K.S.Nguyen , sp. nov. ( Figs. 1 & 3–1 )

Diagnosis: —The new species differs from most similar A. lutea in that it has longer petiole, to 10 cm long, peduncle with 3–4 bracts, perigone tube 16.5–19.5 mm long, incurved perigone lobes, adaxially entirely dark purple violet to almost black, style narrowly cylindrical to filiform, 11–15 mm long, 0.5–0.7 mm in diameter, entirely purple violet, smooth, and flat stigma, less than 2.5 mm in diameter.

Type:— VIETNAM. Type herbarium specimen is prepared from cultivated plants on 4 June 2024, L. Averyanov AL 1651a (holotype LE LE 01276223 https://en.herbariumle.ru/?t=occ&id=229825) originally collected in Bac Kan Province, Ba Be District, Ba Be National Park, dry evergreen broad-leaved old secondary forest with domination of Burretiodendron hsienmu , Streblus asper , Sterculia lanceolata , Polyalthia cerasoides , and Arenga pinnata on crystalline highly eroded rocky limestone at elevation 250–300 m a.s.l., terrestrial herb with epigeous rhizome to 12 cm long on steep rocky slope, leaves dark green with unclear dull light green spots, occasional, 15 November 2022, Nguyen Huu Cuong, Cao Xuan Hai, L. Averyanov, T. Maisak. Photos of plant used for preparation of the type specimen ( LE LE 01255107 https://en.herbariumle.ru/?t=occ&id=226241).

Etymology:— The species epithet refers to the narrowly cylindrical to filiform style, which segregates our plant from all its relatives.

Description: —Perennial, evergreen, terrestrial, rhizomatous herb. Rhizome creeping, semi-woody, plagiotropic, epigeous, terete, (3)4–12(15) cm long, (3)4–6(7) mm in diameter, simple or few-branched, densely nodal, almost naked or covered by sparse, dark dirty brown to almost black remnants of papyraceous scales, with (1)2–3(4) distant erect leaves; each annual sympodium (annual growth) 1-leaved, with 1(2), thick, pale yellowish, somewhat fleshy root. Cataphylls 2–3(4), convolute, tubular, leathery or coriaceous, dark dirty brown violet to almost black, (2)3– 7(8) cm long, 0.5–1 cm wide (when flatten), persistent until anthesis. Leaves petiolate; petiole grassy green, stiffly upright, (4.5)5–8(10) cm long, 3–3.5 mm wide, channeled adaxially; leaf blade upright, arcuate, or almost horizontal, narrowly ovate to elliptic, almost round at base, shortly acuminate at apex, (7)8–16(18) cm long, (4.5)5–6(6.5) cm wide, uniformly dark green, or sometimes with unclear dull light green spots, with prominent median vein and many conspicuous secondary veins on the lower surface, with hardly visible nerves above. Flowers solitary, subsessile, not widely opening, cylindrical in outline, (17)18–22(23) mm long, 6.5–7.5(8) mm in diameter, placed perpendicularly to stem and almost parallel to the ground. Peduncle short, light greenish, (1.4)1.6–7(8) mm long, 1.8–2.2 mm wide, completely hiding by 3–4 tubular bracts; bracts scarious, pure white, or white with light greenish tint toward the apex and finely speckled with light pale purple outside, later dark brown, (9)10–16(17) mm long, (7.5)8–15(17) mm wide (when flattened), obtuse or shortly splitting at the apex. Perigone tube (except perigone lobes) shortly cylindrical, (16.5)17–19(19.5) mm long, (5)5.5–6(6.5) mm in diameter, entirely smooth, white to very light pink outside, purple violet, to almost black inside. Perigone lobes 6, distinctly 2-whorled, subsimilar, smooth, inside without appendages at the base, semi-circular to broadly ovate, (2.8)3(3.2) mm long and wide, concave, round at apex, straight at the base, incurved in apical half, white and heavily speckled with dirty purple outside, entirely dark purple violet inside. Stamens 6; anthers sessile, cylindrical, finger-shaped, (3.9) 4–4.5 mm long, 0.8–1 mm wide, inserted near the middle of perigone tube, with apices placed just below stigma, with pollen sacs oriented to style; pollen pale yellow. Pistil with style narrowly cylindrical to filiform, purple violet, (11)12–14(15) mm long, 0.6–0.7 mm in diameter (0.5 mm wide when dry), shortly widening at the base and at apex; ovary light green, conoid, (1.4)1.6–2(2.2) mm tall and wide; stigma shortly obconoid, with flat, smooth, obscurely hexagonal apex, (1.8)2–2.4(2.5) mm in diameter, dark violet, with 3 radially oriented furcate white lines in the center. Fruits unknown.

Distribution:— Bac Kan Province, Ba Be District, endemic to lowland limestone area of Ba Be National Park.

Ecology and habitat: —Primary and aged secondary, dry, evergreen, broad-leaved forests with domination of Burretiodendron hsienmu , Streblus asper , and Arenga pinnata on solid, highly eroded rocky limestone at elevations of 250–300 m a.s.l., commonly on steep rocky slopes.

Phenology: —Flowers in May–July (in cultivation).

Notes: —The new species belongs to the group of species having narrow tubular flowers, 6 rather short perigone lobes, long sessile or subsessile stamens inserted around the middle of the tube below the stigma, and a cylindrical style, not or hardly broadening into a more or less flat stigma. Among the most typical members of this group, endemic to the limestone mountains of southeast China and northern Vietnam, are such species as Aspidistra angustata Aver., K.S.Nguyen & Tillich in Averyanov et al. (2020a: 2), A. cerina G.Z.Li & S.C.Tang (2002: 289) , A. claviformis Y. Wan (1984b: 166) , A. lingyunensis C.R.Lin & L.F.Guo in Lin et al. (2013: 60), A. lutea Tillich (2005: 320) , A. obconica C.R.Lin & Yan Liu in Lin et al. (2010: 263), and A. saxicola Y. Wan (1984a: 129) . From all species in this group, our plant differs by hardly opening flowers, a truly cylindrical perigone tube, concave incurved perigone lobes, and a narrowly cylindrical to filiform style. Among these similar species, Aspidistra tenuistyla morphologically is most close to A. lutea but differs in petiole to 10 cm long (vs. petiole 4–5 cm), leaf blade pure green or with unclear light green spots (vs. leaf blade with pale yellow marks), perigone tube cylindrical, 16.5–19.5 mm long (vs. obconoid, 8–11 mm long), perigone lobes incurved, adaxially entirely dark purple violet (vs. perigone lobes straight or recurved, yellow or yellow greenish), style entirely purple violet, smooth, narrowly cylindrical to filiform, 11–15 mm long, 0.6–0.7 mm in diameter (vs. style purple violet, with white base, longitudinally ribbed, cylindrical, 8–9 mm long, 1.5–2 mm in diameter), and stigma flat, 1.8–2.5 mm in diameter (vs. stigma slightly concave, 2.5–3 mm in diameter). It is remarkable that the color scheme of the stigma in both species is very similar.

Another similar taxon regarded earlier in the varietal rank of A. lutea is A. luteo-rubra (K.S.Nguyen, Aver. & Tillich) Aver. & K.S.Nguyen , comb. et stat. nov. ≡ Aspidistra lutea var. luteo-rubra K.S.Nguyen, Aver. & Tillich in Averyanov et al. (2020b-e02877: 4, fig. 3). It differs from the type of A. lutea in 1–3-leaved annual sympodium (vs. annual sympodium 1-leaved), petiole 5–9 cm long (vs. petiole 4–5 cm long), leaf blade above uniformly dark green (vs. leaf blade above with marmorated pale yellowish marks), peduncle bracts light green to olive green, 3.5–10 mm long (vs. bracts white with greenish or purple tint, 6–14 mm long), perigone tube inside bright red, 10–14 mm long (vs. perigone tube inside dark purple violet, 8–11 mm long), perigone lobes broadly cordate, 5.5–7.5 mm wide, light yellow greenish heavily speckled with red purple (vs. perigone lobed ovate to broadly ovate, 3–5 mm wide, uniform yellow or yellow greenish), anther inserted at lower third of tube, with anthers apices placed much below stigma (vs. anther inserted at middle of tube, with anther apices placed just below stigma), style cylindrical, obscurely fusiform or clavate, broadest at middle, slightly narrowing to base and apex, 10–12.5 mm long, red purple with white base and apex, smooth (vs. style cylindrical, shortly broadening to base and apex, 8–9 mm long, purple violet with white base, longitudinally ribbed), and stigma circular, flat or slightly convex, 2–2.2 mm in diameter, pure white (vs. stigma obscurely hexagonal, slightly concave, 2.5–3, dark violet, with 3 radially oriented furcate white lines).

and living plants).

Aspidistra tenuistyla described here may be easily segregated from A. luteo-rubra , by 1-leaved annual sympodium (vs. annual sympodium 1-leaved), leaf blade with unclear light green spots (vs. leaves uniformly dark green), peduncle with 3–4 sterile bracts 9–17 mm long (vs. peduncle with 3–6 sterile bracts 3.5–10 mm long), perigone tube cylindrical, 16.5–19.5 mm long, purple violet inside (vs. perigone tube obconoid, 10–14 mm long, bright red inside), perigone lobes semi-circular to broadly ovate, 2.8–3.2 long and wide, incurved, adaxially entirely dark purple violet (vs. perigone lobes broadly cordate, 5.5–7.5 long and wide, straight or recurved, adaxially light yellow greenish heavily speckled with red purple), anther inserted at middle of tube, with anther apices placed just below stigma (vs. anther inserted at lower third of tube, with anther apices placed much below stigma), style narrowly cylindrical to filiform, 11–15 mm long, 0.6–0.7 mm in diameter, entirely purple violet (vs. style cylindrical, obscurely fusiform or clavate, 10–12.5 mm long, 1.8–2.2 mm in diameter, red purple with white base), and stigma obscurely hexagonal, flat, dark violet, with 3 radially oriented furcate white lines (vs. circular, convex, pure white).

The detailed comparison of morphological characters of all three species based on studies of currently available materials is presented in figures 1 & 2, and Table 2 (as well as Averyanov et al. 2020b: 5, Fig. 3 ; LE LE01055464 https://en.herbariumle.ru/?t=occ&id=5840) clearly supports the taxonomic status of the mentioned plants as a separate, well-segregated species. All three studied species are endemics of limestone areas of northern Vietnam, and each is known presently by a lone type location ( Fig. 3 ) .

The flowers of Aspidistra tenuistyla superficially look similar to those of A. longituba Liu & Lin (2011: 519) reported from southeast China. However, our plant differs in spaced leaves on long rhizomes with 1-leaved annual sympodia (vs. leaves densely tufted on rhizomes, annual sympodia bear usually more than 1 leaf) and in the smooth adaxial surface of the perigone tube and perigone lobes (vs. perigone lobes bear inside at their bases distinct appendages closing aperture in the perigone throat).

Conservation: —According to currently available data, Aspidistra tenuistyla is a rather uncommon plant. The species inhabits lowland limestone forests at elevations of 250–300 m a.s.l. in the officially protected area of Ba Be National Park. It’s presently observed and documented that the extent of occurrence (EOO) and area of occupancy (AOO) are obviously less than 100 km ² and 10 km ² respectively. Despite official protection of the territory harboring the species population, it may be negatively influenced by recreation and other expansions of tourism activity. Before special studies, the conservation status of the new species may be tentatively estimated as Near Threatened (NT) following the criteria of the IUCN Red List (2024).

Studied specimens:— Aspidistra lutea Tillich. VIETNAM, in cultivation at the Botanical Garden Munich, accession-nr 96/3126 plant collected by Nikolai Arnautov in Vietnam, Prov. Son La, Ban Sai, 1976 (Arnautov 76– 140), [herbarium voucher specimen prepared in] August 2005 Tillich 5003, [“clonotype”] (LE LE01049990 https:// en.herbariumle.ru/?t=occ&id=3119). VIETNAM, collected by N. Arnautov (Arnautov 76–140) in Vietnam, Prov. Son La, Thuan Chau, Ban Sai, 700–800 m, 1976, flowered under cultivation [and herbarium voucher specimen prepared] in 25 July 2018, L. Averyanov 76–140.1 [“clonotype”] (LE LE01048623 https://en.herbariumle.ru/?t=occ&id=430, photos LE LE0107313 https://en.herbariumle.ru/?t=occ&id=15418). Aspidistra luteo-rubra (K.S.Nguyen, Aver. & Tillich) Aver. & K.S.Nguyen. VIETNAM, Hoa Binh Province, Lac Son District, Ngoc Son–Ngo Luong Nature Reserve, Tu Do Commune, Coi Gao Village, logged closed primary evergreen broad-leaved lowland forests on limestone around point 20°26′55.8″N, 105°16′24.8″E, 560 m a.s.l, perennial herb, terrestrial or lithophytic, 15–30 cm in tall, growing on steep slope or near top of limestone mountains, leaves dark green adaxially, pale or olive green abaxially, with yellow spots, 4 Dec 2017, N.Q. Hieu et al., herbarium specimen prepared from cultivated plant, 4 April 2018, K.S. Nguyen, CK 1711b (holotype HN, photos of living plants, flowers and floral details prior preparation of the type CK 1711b: LE (LE01055464 http://en.herbariumle.ru/?t=occ&id=5840).

Figures

FIGURE 1. Aspidistra tenuistyla Aver. & C.H.Nguyen. A. Whole plant in cultivation. B. Flattened flowering plant prior the preparation of the type herbarium specimen. C. Leaf, adaxial side. D, E. Rhizome with fully open flowers. F. Intact flower on rhizome, side view. G. Fresh floral bracts. H. Flattened dry floral bracts. I. Separated flower with peduncle covered by floral bracts, side view. J. Peduncle and flower, side view, floral bracts removed. K. Fully open flowers, frontal view. L. Longitudinal tangential section of flower showing pistil. M, N. Longitudinal tangential section of flower showing anthers. O. Pistils, side view. P. Stigma, view from different sides. Photos by L. Averyanov, made from the plant used for the preparation of the type specimen L. Averyanov AL1651a, correction and design by L. Averyanov and T. Maisak.

FIGURE. 3. Distribution of Aspidistra tenuistyla, A. lutea, and A. luteo-rubra. 1. Aspidistra tenuistyla (Bac Kan Province, Ba Be District, Ba Be National Park). 2. A. lutea (Son La Province, Thuan Chau, Ban Sai). 3. A. luteo-rubra (Hoa Binh Province, Lac Son District, Ngoc Son – Ngo Luong Nature Reserve, Tu Do Commune, Coi Gao Village). Map compiled by L. Averyanov.