Phaius duongae Aver, V.C.Nguyen & Vuong, 2023

Nguyen, Thi Lien Thuong, Averyanov, Leonid V., Maisak, Tatiana V., Nguyen, Van Canh, Nguyen, Van Khuong, Pham, Thi Thanh Dat, Nguyen, Danh Duc & Truong, Ba Vuong, 2023, Phaius Duongae (Orchidaceae, Collabieae), A New Cauline Species From Southern Vietnam, Phytotaxa 606 (1), pp. 73-78 : 74-77

Phaius duongae Aver, V.C.Nguyen & Vuong , sp. nov.

( Figs. 1 & 2 )

Diagnosis: —New species differs from closest P. hekouensis in short stem, less than 45 cm long, smaller leaves less than 34 cm long, short, 2–3-flowered inflorescence, pale pink or pink purple flowers, and saccate spur 3–4.5 mm long.

Type: — VIETNAM. Herbarium specimen prepared from cultivated plant on 3 January 2023 by Nguyen Van Canh AL 2050 (holotype LE01168155 https://en.herbariumle.ru/?t=occ&id=170353, LE01170557 https://en.herbariumle. ru/?t=occ&id=170367), analytical photos from living plants used for the preparation of the type specimen and drawing LE01124196 https://en.herbariumle.ru/?t=occ&id=170141, LE01124205 https://en.herbariumle.ru/?t=occ&id=172285) originally collected in Da Nang City Area, Ba Na Natural Reserve , evergreen forest on granite along stream, at an elevation of about 1000 m a.s.l., terrestrial herb, flowers pink, March 2021, Nguyen Van Canh s.n .

Paratypes: — VIETNAM, wild collected plant cultivated in Nguyen Van Canh garden originated from Da Nang City Area, Ba Na Natural Reserve , January 2022, N. V . Canh s.n. AL 1567 ( LE01169117 https://en.herbariumle.ru/?t=occ&id=140973, LE01169116 https://en.herbariumle.ru/?t=occ&id=140970) . VIETNAM, analytical photos were taken from specimen prepared from cultivated plant on 4 January 2022 by Truong Ba Vuong, Nguyen Van Canh BV 1346, originally collected in Da Nang City Area, Ba Na Natural Reserve , March 2021, Nguyen Van Canh s.n. (photos LE01124206 https://en.herbariumle.ru/?t=occ&id=172286) . VIETNAM, specimen prepared from cultivated plant originally collected in Kon Tum Province, Tu Mo Rong District, Ngoc Lay Commune , 4 January 2022, Truong Ba Vuong, Nguyen Van Canh, BV 1346 ( VNM00065792 ) . VIETNAM, photo made in 29 May 2022 by L . Averyanov , N. V . Canh and T . Maisak from wild collected plants cultivated in Nguyen Van Canh garden originated from Da Nang City Area, Hoa Vang District , N. V . Canh s.n., flowers white, lip with yellow spot at center, 29 05 2022, L . Averyanov , N. V . Canh , T . Maisak, AL 1341 ( LE01169123 https://en.herbariumle.ru/?t=occ&id=140987, photos LE01123413 https:// en.herbariumle.ru/?t=occ&id=137203) .

Etymology: —The species name is proposed by plant discoverer, Nguyen Van Canh after his beloved mother Mrs. Phan Thi Duong.

Description:—Herb terrestrial, perennial, with short plagiotropic rhizome, and several erect stems close together. Stems erect, green, terete, fleshy, (25)30–40(45) cm long, 0.8–1.4 cm in diameter; basal half with 3–5(6) tubular grassy green acute bracts, 1–6(7) cm long, each with many prominent veins; upper half leafy, covered by imbricate overlapping sheaths of (4)5–6(7) leaves approximated near the apex. Leaves subsessile to petiolate, with broadly elliptic, acute to shortly acuminate leaf blade, (15)20–30 (34) cm long, (4)5–10(11) cm wide; at the base narrowing into a sheathing petiole (3)5–12(14) cm long and tubular leaf sheath, (3)4–6(7) cm long, 1–2.5(3) 4 cm in diameter, enveloping stem. Inflorescence arising from upper leaf axils near the stem apex, dark green, erect, (8)10–12(14) cm long, bearing 2–3 flowers; flower bracts early caducous, thin, light green, cymbiform, 2–3 cm long, 0.8–1.2 cm wide (being flattened), acute; rachis (2)3.5–4.5(5) cm long, slightly zig-zag. Flowers widely opening, 6–7 cm across, entirely uniform pale pink to pale pink purple, lip with yellow longitudinal callus. Sepals subsimilar, oblong elliptic, (3.2)3.4–3.8(4) cm long, 1–1.2 cm wide, keeled outside, acute, slightly cucullate. Petals broadly oblanceolate, as long as sepals, (6.5)7–8(8.5) mm broad, blunt to round at apex. Lip obscurely 3-lobed, round in outline (being flattened) with narrowing base, (3.2)3.6–4(4.4) cm long (including spur), (2.4)2.6–3(3.4) cm wide, shortly adnate to column at base for (5)6–7(8) mm, margin at front strongly undulate and plicate, with distinct longitudinal channel abaxially; side lobes half ovate to half circular, (1.4)1.6–2(2.2) cm long, (6)7–9(10) mm wide; median lobe half circular, (6)7–8(9) mm long, (1.2)1.4–1.6(1.8) cm wide, slightly emarginate with central triangular tooth; disc with 2 massive fleshy, scurfy haired, longitudinal keels separated by the narrow split and single fleshy, triangular, verruculose callus at apex; spur shortly conoid to saccate, (3)3.5–4(4.5) mm long, 2–2.5 mm in diameter, with short scurfy hairs and a large callus at spur entrance. Column yellowish on sides, pink at front, stout, slightly curved, (1.7)1.8–2(2.2) cm tall, broadening apically to (5.5)6–7(7.5) mm wide, slightly winged, clinandrium irregularly tooted along the margin; stigma scutelliform, obscurely circular, rostellum broadly ovate, hanging; anther cap helmet shaped, 2–2.2 mm in diameter, finely verruculose. Pollinia 8, in 2 groups, obovate, shortly attenuate at the base, ca. 2 mm long. Fruits unknown.

Ecology and phenology: —Primary and old secondary broad-leaved evergreen forests on granite at an elevation about 1000 m a.s.l., usually along small forest streams. Not common. Flowers in March–June.

Distribution: — VIETNAM, Da Nang City Area (Ba Na Natural Reserve, Hoa Vang District) and Kon Tum Province (Tu Mo Rong District, Ngoc Lay Commune). Endemic. According to undocumented observations by the authors, the species also occurs in Quang Nam Province.

Conservation status: —According to available collections and field observations the extent of occurrence (EOO) of the new species can includes a large territory in the center of Vietnam including Da Nang City Area , Quang Nam, Quang Ngai and Kon Tum provinces with total approximate square about 27000 km 2. However, any data for its locations are very scarce and not well documented, which indicate the conservation species status as Data Deficient (DD) according to terms and criteria proposed by IUCN (2022).

Notes: —The species is remarkable and easy recognizable for its large uniform pink or pink purple flowers with massive yellow callus on the lip. This species in its morphological characters looks most close to P. hekouensis according to identification key, description and excellent illustrations presented in the recent monographic study of the genus ( Stone & Cribb 2017). From P. hekouensis hitherto known from very small area in SE Yunnan our plant differs in shorter stem, less than 45 cm long (vs. stem of mature plants 1–1.3 m long), smaller leaves less than 34 cm long (vs. leaves to 55 cm long), inflorescence 8–14 cm long, with 2–3 flowers (vs. inflorescence about 25 cm long with 4–5 flowers), flowers entirely uniform light pink to light pink purple (vs. flowers yellow, lip with red markings), spur shortly conoid to saccate, 3–4.5 mm long (vs. spur cylindrical conoid, 11 mm long), column less than 2.2 cm tall with anther cap 2–2.2 mm wide (vs. column 2.3 cm long with anther cap 3 mm wide). According to currently available data, our new species is rare endemic of the central part of Vietnam outlined in plant geography of Indochina as the Central Annamese Province Floristic Province (Averyanov et al. 2003).

Figures

FIGURE 1. Phaius duongae Aver, V.C.Nguyen & Vuong, sp. nov. A. Flowering plant. B. Basal part of the stem. C. Middle part of the stem. D. Intact flowers. E. Detached flower, frontal view. F. Ovary, column and lip, side view, and view from above. G. Lip, and column apex, frontal view. H. Median sepal, abaxial and adaxial side. I. Lateral sepals, abaxial and adaxial sides. J. Petals, abaxial and adaxial sides. K. Lip, adaxial side. L. Keel on lip disc. M. Keel, frontal view of the disc. N & O. Surface of the disc and keel. P. Column, frontal and side view. Q. Lip apex with and without operculum. R. Anther cap, view from above and from below. S. Pollinarium, view from different sides. Photos of Nguyen Van Canh (A, C, D, specimen AL 2050) and Truong Ba Vuong (B, E–S, specimen BV 1376), photo correction and design by L. Averyanov and T. Maisak.

FIGURE 2. Phaius duongae Aver, V.C. Nguyen & Vuong, sp. nov. A. Flowering plant. B. Flower, frontal and side view. C. Flattened flower, lip removed. D. Lip, adaxial and abaxial surface. E. Keel on the lip disc. F. Transversal section of the keel in the middle part of the disc. G. Column, half-side and frontal view.All are drawn from the type specimen Nguyen Van Canh AL 2050 by L. Averyanov.