Aspidistra erosa Aver., Tillich, T.A. Le & K.S. Nguyen, 2019

Averyanov, Leonid V., Le, Tuan Anh, Nguyen, Khang Sinh, Tillich, Hans-Juergen, Nguyen, Danh Duc, Hoang, Le Tuan Anh, Tran, Hoang Dung, Dat, Pham Thi Thanh & Maisak, Tatiana V., 2019, Aspidistra erosa, A. sarcantha, and A. verruculosa (Asparagaceae), three new species from Vietnam, Phytotaxa 404 (3), pp. 102-110 : 102-106

Aspidistra erosa Aver., Tillich, T.A. Le & K.S. Nguyen , sp. nov. ( Fig. 1 )

Type: — VIETNAM. Central Vietnam, Quang Binh province, Minh Hoa district, Hong Hoa commune, 17.883333°N 105.95975°E, primary evergreen forest on sandy alluvial terrace and slopes of river valley between karstic limestone hills at elevation of 90–100 m a.s.l., common, 24 November 2018, Pham Thi Thanh Dat, Le Tuan Anh, LTA 818 (holotype LE01048497 !; isotypes LE01049331 !, VNMN!) .

Paratype: — VIETNAM. Central Vietnam, Quang Binh province, Minh Hoa district., Hong Hoa commune, 17.883341°N 105.95960°E, elevation 100–110 m a.s.l. Secondary evergreen broad-leaved forest at the base and on slope of limestone mountains, terrestrial perennial rhizomatous herb with erect leaves 30–70 cm tall, adaxial perigone lobes dark purple-violet, abaxial perigone tube and lobes dull white or milky, stigma white, mushroom shaped, common, 2 December 2018, Nguyen Sinh Khang, Hoang Thanh Son, Bui Tien Dat, NSK 1147 ( HN!).

Etymology:—Species epithet refers to the erose margin of perigone lobe apex.

Description: —Terrestrial perennial rhizomatous herb 30–70 cm tall. Rhizome terete, creeping, plagiotropic or distally ascending, simple or occasionally branching, (6)8–10(12) mm in diameter, to 20 cm long, consists of several many-noded sympodial segments (1.0)1.5–3.0(3.5) cm long terminated at ascending apex by 1(2) erect leaf. Roots spaced throughout rhizome, thick, rigid, light gray, semi-woody, straight or flexuose. Cataphylls convolute, cuneate, (6)10–12(14) cm long and 0.8–1.0 cm wide (being flattened), young grassy green, coriaceous, later withered, papyraceous, dull light grey or pale brownish, early splitting into irregular fibres, enveloping petioles by fibrouspapyraceous remains. Leaves petiolate, (30)40–60(70) cm tall. Petiole stiff, erect, almost straight, (18)20–30(32) cm long. Leaf blade upright, suberect or somewhat arching, lanceolate to broadly lanceolate tapering to the base and apex, (22)28–35(42) cm long, (2.8)3.0–3.5(4.0) cm wide, plicate, uniformly dull green above and below, with prominent midvein and 3–5 secondary veins well seen on both sides, arising from midvein in basal half of leaf blade. Flowers appear on individual stem commonly by 1–2 (occasionally to 5–6) in one time, pedunculate, kept nearly horizontal or obliquely on erect peduncle, widely open, (12)14–15(16) mm in diameter. Peduncles appearing solitary on apical sympodial rhizome segment just below the foliage leaves, pale green mottled with dirty purple, (2.0)3.5–4.0(5.0) cm long, 1.0– 1.5 mm in diameter, erect or obliquely ascending (with fruits becoming nutant or horizontal); each peduncle with 1(2) bracts near the middle and 2–3 bracts at the base and apex; bracts triangular ovate, tubular or concave, papyraceous or scarious, often partially lacerate, dull brownish, obtuse to blunt, (4)6–8(10) mm long and (2.5)5.0(6.0) mm wide (when flattened). Perigone tube campanulate to slightly urceolate, (5.5)6.0(6.5) mm long, (7.5)8.0(8.5) mm wide, glossy, milky white outside, dark purple-violet inside, with pure white filaments. Perigone lobes 6, subequal, broadly triangular ovate, in two whorls, slightly convex, blunt to almost round at apex, fleshy, smooth, suberect to recurved, (5.5)6.0(6.5) mm long, (4.5)5.0(5.5) mm wide, at apex with hyaline eroded or irregularly denticulate margin, abaxially with 5–7 slightly sunken distinct veins, adaxial surface smooth, glossy dark purple-violet, little lighter toward the apex, abaxial surface white at center, dark purple-violet along the margin or entirely purple-violet. Stamens 6, about 4 mm long, filaments and connective fleshy, pure white. connivent to tube wall from base to middle of tube, filaments (1.8)2.0–2.2(2.4) mm long, laterally about 2 mm apart from each other; pollen sacs bean-shaped, (1.8)2.0(2.2) mm long, (1.2)1.3–1.4(1.5) mm wide, facing the style, pollen pale yellow. Pistil mushroom-shaped; ovary inconspicuous, white to light greenish; style rather slender, white, cylindrical, (4.5)4.8–5.2(5.4) mm tall, (1.0)1.1–1.2(1.3) mm in diameter, upcurved; stigma hemispherical, fleshy, white, finely purple spotted at lower side, orbicular, weakly 6-lobed, (5.4)5.6–5.8(6.0) mm in diameter, its upper surface smooth, sometime with 3 hardly visible irregular radial fissures. Fruits unknown.

Habitat, phenology and conservation status:—Primary and secondary evergreen broad-leaved lowland forest on sandy alluvial terrace and slopes of river valley between karstic limestone hills at elevation of 90–100 m a.s.l. Locally common. Flowering in October–November. Incomplete field observations on species distribution and its rarity make this taxon difficult to assess, hence it should be categorized as DD (Data Deficient) according to IUCN Red List criteria ( IUCN 2017).

Distribution:—Central Vietnam (Quang Binh province, Minh Hoa district). Endemic of central Vietnam.

Similar species:—The new species is morphologically similar to Aspidistra multiflora Averyanov & Tillich (2015: 368) and Aspidistra zinaidae Averyanov & Tillich (2012: 8) , two species growing in central part of Vietnam, in Thanh Hoa and Thua Thien-Hue provinces, respectively. However, A. erosa differs from both these species in the following features: rhizomatous plagiotropic stem, creeping to distally ascending (vs. a stem almost orthotropic, erect or suberect), leaves lanceolate to broadly lanceolate (vs. leaves narrowly elliptic to elliptic), flowers commonly one or two (vs. regularly many flowers sprouting from the rhizome apex at one time), peduncles more or less erect, flowers 12–16 mm in diameter (vs. peduncles more or less horizontal, flowers less than 12 mm in diameter), flower in horizontal or oblique position (vs. flowers horizontal in A. zinaidae or obliquely erect in A. multiflora ), perigone lobes outside with 5–7 slightly sunken distinct veins (vs. 3 veins), apex of perigone lobes with erose to irregularly denticulate margin (vs. margin of perigone lobes entire), connectives about 2 mm distant from each other (vs. connectives strongly fleshy, about 0.5 mm distant from each other), style slender, upcurved (vs. stout, straight).

It is not easy to distinguish A. erosa form other closely related species, such as A. zinaidae and A. multiflora . Indeed, it shares with A. zinaidae and A. multiflora conspicuous stamens with more or less fleshy white filaments and connectives connivent to the tube wall from the base to the middle of the tube. Furthermore, also the shape and color of the tube, the perigone lobes in two whorls, and the mushroom-shaped pistil are features in common among these three species. A somewhat more remote similarity exists with A. heterocarpa Aver., Tillich & V.T. Pham ( Averyanov et al. 2018b: 1), as it shares with this latter species the shape and color of the perigone tube as well as the white, fleshy filaments connivent to the tube wall, while the connective is not remarkably enlarged, the pollen sacs are narrowly ovate, and the sigma is capitate. These four species may be informally named the Aspidistra zinaidae group. As concerns the relationships among these species, it seems that the morphological distance between A. zinaidae and A. multiflora is comparable to that between A. zinaidae and A. erosa , or A. multiflora and A. erosa . This implies that either A. erosa is a species of its own, or, alternatively, A. multiflora and A. erosa fall within the variability of A. zinaidae . However, a series of small morphological features look quite stable, so that we prefer to describe A. erosa as a separate species. Further field studies may reassess our present vision.

Figures

FIGURE 1. Aspidistra erosa Aver., Tillich, T.A. Le & K.S. Nguyen, sp. nov. (picture of the plate made from LTA 818). Photos by Tuan Anh Le, correction and design by L. Averyanov and T. Maisak.