Myrmechis brachyscapa Aver., Vuong & Ormerod, 2023

Averyanov, Leonid V., Nguyen, Van Canh, Vuong, Truong Ba, Nguyen, Khang Sinh, Nuraliev, Maxim S., Nguyen, Cuong Huu, Ormerod, Paul A., Maisak, Tatiana V., Diep, Dinh Quang, Lyskov, Dmitry F. & Nong, Duy Van, 2023, New orchids in the flora of Vietnam VII (Orchidaceae: tribes Cypripedieae, Cranichideae, Orchideae, and Collabieae), Phytotaxa 619 (4), pp. 255-276 : 260-263

Myrmechis brachyscapa Aver., Vuong & Ormerod , sp. nov.

( Fig. 3 )

Diagnosis:—The new species differs from the most morphologically close M. longii in glabrous inflorescence, narrowly oblong sepals 9–11 mm long, subquadrate to shortly rectangular epichile lobes, finger-like column wings, large rostellar arms as long as the column, long beaked anther cap with beak 2.2–2.4 mm long, and pollinia entire at apex.

Type:— VIETNAM. Ha Giang Province: Vi Xuyen District, Minh Tan Commune, terrestrial orchid, elevation about 1000 m, 14 May 2023, Truong Ba Vuong , Vang Di Thao s.n. (holotype VNM00063983 , isotype LE, photos LE01124209 https://en.herbariumle.ru/?t=occ&id=173652) .

Paratypes: — VIETNAM. Nghe An Province: Ky Son District, Na Ngoi Municipality, eastern slopes of Phu Xai Lai Leng Mountain , primary very humid broad-leaved forest on steep mountain slopes composed of sandstone and gray shale at elevations of 2000–2300 m, around point 19°11′58.2″N 104°11′38.6″E, common, 24 October 2013, L.Averyanov, N. T.Hiep, N. S.Khang et al. CPC 6195 ( LE01076840 , https://en.herbariumle.ru/?t=occ&id=57718) . VIETNAM. Nghe An Province: Ky Son District, Na Ngoi Municipality, eastern slopes of Phu Xai Lai Leng Mountain , primary very humid broad-leaved forest on steep mountain slopes composed of sandstone and gray shale at elevation of about 2300 m, around point 19°12′23.3″N 104°11′33.7″E, terrestrial creeping herb, flowers white, common, 24 October 2013, L.Averyanov, N. T.Hiep, N. S.Khang et al. CPC 6227 ( LE01076836 https://en.herbariumle.ru/?t=occ&id=57714) .

Etymology:—The species name refers to its remarkably short peduncle.

Description:—Terrestrial herb with creeping plagiotropic rhizome and glabrous ascending leafy floriferous stem. Rhizome dull brownish purple, terete, (2)3–4(5) cm long, (1)1.2–1.8(2) mm in diameter, without swellings, rootless, with tufts of root hairs at nodes. Floriferous stem slender, suberect, (3)3.5–5(5.5) cm tall, with 3–4(5) distant leaves. Leaves glabrous, shortly petiolate; petiole and sheath (1.5)2–3.5(4) mm long, 1.5–2 mm wide; leaf blade narrowly to broadly ovate, or obscurely triangular, tapering to obtuse or acute apex, (6)8–18(20) mm long, (4)5–8(9) mm wide, adaxially velvety dark green to almost black, with white median longitudinal stripe, abaxially uniformly dull pink to purple. Peduncle erect, (2.5)3–5(5.5) mm long, with 1–3 small scale-like leaves at base and 1 reddish pink cuneate, acuminate sterile bract near middle; rachis 1–2-flowered, to 3.5 mm long. Floral bracts dull pink, scarious, triangular ovate, cymbiform, acuminate, (4.5)5–6(7) mm long, (1.6)1.8–2(2.2) mm wide, finely ciliate along margin, glabrous on both surfaces. Flowers sessile, white, resupinate, hardly opening, (8)8.5–9.5(10) mm long; sepals and petals glabrous, joined from base to 1/3 of their length. Ovary dull reddish brown, cylindrical, twisted, straight, erect, (6)6.5–8.5(9) mm long, (1.9)2–2.2(2.3) mm in diameter, glabrous. Sepals subequal, forward directed, narrowly oblong, blunt or roundish at apex, (9)9.5–10.5(11) mm long, (2.2)2.4–2.6(2.8) mm wide; lateral sepals slightly oblique. Petals narrowly oblong spatulate, as long as and a little wider than sepals, roundish or truncate at apex, forming with median sepal forward directed hood-like structure. Lip fleshy, (6.2)7–8(8.2) mm long, distinctly divided into hypochile, mesochile and epichile; hypochile cup-shaped, 2.6–2.8 mm in diameter, near the base, on each side with massive, shortly conoid, bidentate gland; mesochile oblong rectangular, (3.6)3.8–4(4.2) mm long, 1.4–1.6 mm wide, with involute, finely papillose margins; epichile conduplicate, 1.6–1.8 mm long, 4–4.2 mm wide (being flattened), 2–lobed, with erect, hardly spreading lobes, each lobe subquadrate to shortly rectangular, slightly oblique, 1.6–1.8 mm long, 1.3–1.4 mm wide. Column stout, shortly cylindrical, 3.8–4.2 mm long, about 1.8 mm wide, at front with 2 prominent, finger-like wings, at apex with 2 large, forward directed rostellar arms and with large hemispheric stigma on each side. Anther cap narrowly ovate, concave, 1.5–1.7 mm long, 1.2–1.4 mm wide, at front with long narrow, acuminate red beak 2.2–2.4 mm long; pollinarium with 2 clavate pollinia placed on common slender caudicle 1.6–1.8 mm long, with oblong viscidium placed at the middle of caudicle; pollinia 1.8–2 mm long, entire at apex. Capsule erect, fusiform, 6-ribbed, (8)10–12(13) mm long, (2.8)3–3.4(3.6) mm in diameter.

Ecology and phenology:—Evergreen broad-leaved humid submontane and montane forests on limestone, sandstone, and shale at elevations of 1000–2300 m a.s.l. Flowers in May, fruits in October.

Distribution:—Endemic to Vietnam (provinces Ha Giang: Vi Xuyen District; and Nghe An: Ky Son District).

Conservation status:— Myrmechis brachyscapa is known in two locations of northern Vietnam in Ha Giang and Nghe An provinces. These locations are about 450 km apart from each other. In these locations, three populations were found in undisturbed primary forests where they presently do not meet any direct threat. Meanwhile , the species is strongly habitat-dependent and is likely to extinct fast under deforestation widely observed in the areas of its occurrence. We estimate the conservation status of this species as Near Threatened (NT) according to the criteria proposed by the IUCN Red List (2023).

Notes:—The genus Myrmechis (Lindley 1840: 500) Blume (1858: 76) is sometimes merged within Odontochilus Blume (1858: 79) on the basis of somewhat uncertain morphological and molecular data ( Yukawa 2016, Govaerts et al. 2023). At the same time, Myrmechis is readily distinguished morphologically from Odontochilus in rootless rhizome (vs. rhizome with roots at nodes), stem usually less than 5–6 cm tall (vs. stem commonly much longer than 10 cm), peduncle usually less than 1–2 cm long (vs. peduncle much longer than 2 cm) bearing 1–2 (vs. several) sterile bracts, flowers tubular (vs. with reflexed lateral sepals and well exposed lip), sepals and petals fused at base (vs. sepals and petals free), mesochile without any lateral fringes or teeth (vs. mesochile laterally with fringes or teeth), hypochile on each side with a single massive gland half as large as a hypochile (vs. gland or several glands on sides of hypochile are rather slender, much less than a half of the hypochile diameter). Myrmechis is also morphologically close to Cheirostylis Blume (1825: 413) , from which it differs in slender rhizome (vs. rhizome with inflated, succulent segments), leaves usually crowded at the base of the erect floriferous stem (vs. leaves widely spaced along stem), peduncle shorter (vs. several times longer) than the largest leaves, hypochile on each side with a single massive gland (vs. hypochile usually with one or several slender glands), mesochile in the form of an incomplete tube between the hypochile and epichile, much longer than 1 mm (vs. mesochile in the form of a constriction between the hypochile and epichile, usually about 1 mm long), epichile bilobed conduplicate with simple oblong or rectangular lobes (vs. epichile almost flat, bilobed or subentire, toothed, laciniate or fringed along the margin). Since these three genera are quite clearly segregated on the basis of morphological characters, we here follow their traditional delimitation.

Myrmechis brachyscapa is probably most close to the recently described M. longii J.D.Ya in Ya et al. (2021: 365) endemic to SE Yunnan (Wenshan Prefecture, Malipo County). The two species share similar plant habit, dark leaves with white longitudinal stripe, very short peduncle bearing 1–2 hardly opening flowers, 2-lobed epichile, massive hypochile glands bidentate at the apex, and oblong viscidium attached to the middle of caudicle. The new species differs from M. longii in glabrous inflorescence (vs. peduncle and rachis sparsely villous), sepals narrowly oblong, 9–11 mm long (vs. narrowly ovate or ovate, 4.8–5 mm long), lobes of epichile subquadrate to shortly rectangular, 1.6–1.8 mm long (vs. oblong lanceolate, 4–4.2 mm long), column with finger-like wings and large rostellar arms as long as the column (vs. column wings short, semicircular, rostellar arms insignificant, much shorter than column), anther cap narrowly ovate, at front with red narrowly acuminate beak 2.2–2.4 mm long (vs. anther cap ovate, at front with green triangular beak less than 1 mm long), and pollinia entire (vs. bifid) at apex. Myrmechis brachyscapa is also close in floral morphology to M. pumila ( Hooker 1890: 99) Tang & Wang (1951: 69) (= Zeuxine langbianensis Tich in Nguyen 2001: 214, see Averyanov 2008) widely distributed in tropical mainland SE Asia, but differs in velvety leaves with white median stripe (vs. leaves uniformly green), glabrous peduncle, rachis, floral bracts and ovary (vs. hairy), peduncle not more than 5.5 mm long (vs. peduncle longer than 5.5 mm), 1–2-flowered inflorescence (vs. inflorescence normally with more than 2 flowers), flowers 8–10 mm long (vs. 5–6 mm long), subquadrate to shortly rectangular (vs. obovate) lip lobes, column with large rostellar arms as long as the column (vs. rostellar arms much shorter than column), beak of anther cap red, narrowly acuminate, 2.2–2.4 mm long (vs. beak of anther cap dull greenish, triangular, less than 1 mm long), and viscidium attached to the middle of the caudicle (vs. viscidium is placed at the base of the caudicle).

Myrmechis urceolata Tang & K.Y.Lang in Lang (1996: 638), Chen et al. (2009: 65), Zhou et al. (2016: 89). Type:— CHINA. Guangdong Province: Xinyi City, flowers white, 19 May 1931, S.P.Ko 51443 (syntypes IBSC0637090, PE00522794, PE00522795).

( Figs. 1 D–H )

≡ Odontochilus urceolatus (Tang & K.Y.Lang) Yukawa (2016: 108) .

Ecology and phenology:—Miniature terrestrial and lithophytic creeping herb. Evergreen broad-leaved montane forests on granite, commonly among moss cover, at elevations of 500 ( Chen et al. 2009) to possibly 2500 m a.s.l. Flowers in May–July.

Distribution:— Vietnam (Lao Cai Province: Fansipan Mountain). South China.

Conservation status in Vietnam:—The species is known in Vietnam from a single location with an unknown number of mature individuals. Pending comprehensive field studies in this area, we estimate the national conservation status of the species as Data Deficient (DD) according to the criteria proposed by the IUCN Standards and Petitions Committee (2023).

Notes:— Myrmechis urceolata is reported here as a new record for the flora of Vietnam. This discovery was rather expectable, since the species was earlier known in similar habitats in southern China, including SE Yunnan, Guangdong and Hainan. In Vietnam, the species is very rare.

Studied specimen:— VIETNAM. Lao Cai Province: Fansipan Mt. , 23 June 2019, Truong Ba Vuong, Nguyen Thanh Luan AL 1237 ( LE01066675 https://en.herbariumle.ru/?t=occ&id=12433) .

Figures

FIGURE 1. Paphiopedilum barbigerum var. barbigerum. A. Flowering plant in natural habitat. B & C. Flowers, front view. Specimen: L.T.Van, K.S.Nguyen AL 1605. Myrmechis urceolata. D. Flattened flowering and fruiting plants. E & F. Apical part of floriferous stem with flowers. G & H. Flowers and flower buds, side and front view. Specimen: T.B.Vuong, N.T.Luan AL 1237. Peristylus affinis. I. Flattened plant. J. Portion of inflorescence. K. Flower, side view. L. Detached flower, side view, with sepals removed. M. Detached flower, sagittal section. N. Detached flattened sepals, petals and lip. Specimen: S.K.Nguyen, T.H.Nguyen, M.H.Giang NSK 950. Photos by L.T.Van & K.S.Nguyen (A–C), T.B.Vuong (D–H) and K.S.Nguyen (I–N); photo correction and design by L.Averyanov and T.Maisak.

FIGURE 3. Myrmechis brachyscapa. A. Flowering plant in nature. B. Apical part of stem and inflorescence. C. Flattened flowering plants. D. Rhizome and basal part of stem. E. Leaves, adaxial and abaxial side. F. Floral bract. G. Inflorescence with intact flower, view from above. H. Flower, views from different sides. I. Median sepal and petals, side view. J. Column and lateral sepal. K. Column and lip, side view. L. Separated median sepal and petals, abaxial and adaxial side. M. Lateral sepal, adaxial side. N. Lip, views from different sides. O. Mesochile. P. Hypochile with internal glands. Q. Column, views from different sides. R. Anther cap, views from different sides. S. Pollinarium, views from different sides. Photos by T.B.Vuong and V.D.Thao made from plants used for the preparation of the type specimen (T.B.Vuong, V.D.Thao s.n.), photo correction and design by L.Averyanov and T.Maisak.