Danxiaorchis mangdangshanensis Q. S. Huang, Miao Zhang, B. Hua Chen & Wang Wu, 2022

Zhang, Miao, Zhang, Xiao-Hui, Ge, Chang-Li & Chen, Bing-Hua, 2022, Danxiaorchis mangdangshanensis (Orchidaceae, Epidendroideae), a new species from central Fujian Province based on morphological and genomic data, PhytoKeys 212, pp. 37-55 : 37

Danxiaorchis mangdangshanensis Q. S. Huang, Miao Zhang, B. Hua Chen & Wang Wu sp. nov.

Figs 3 , 4 , 5

Diagnosis.

Danxiaorchis mangdangshanensis can be easily distinguished from D. singchiana by having no fine roots, fewer flowers in the raceme, the side lobes of the labellum are ivory-white rather than yellow, and it has only 3 colored strips rather than 4-5 pairs. Additionally, its callus is a less distinctive Y-shape and has three auricles, with a purple-red spot on each auricle at the front, and the callus has a remarkable striped appendage adaxially. Furthermore, there are narrow wings on the side of column, and the four pollinia are narrowly elliptic in shape and equal in size.

Type.

China. Fujian (福建) Province, Nanping (南平) City , Yanping (延平) District , Mangdangshan Mountain , Mangdangshan National Nature Reserve , forest margins, 26°41'N, 118°2'E, elevation 375 m, 5 May 2022, Q.S. Huang & B. Hua Chen CBH 04593 (Holotype, FNU, barcode FNU0041324; Isotypes, FNU, barcode FNU0041325) .

Description.

Plant erect, 10.6-22.2 cm tall, holomycotrophic. Rhizome tuberous, fleshy, cylindrical, 2.5-5.3 cm long, 7.0-11.2 mm thick, with short branches, 4.5-5.6 mm long, without roots. Scape terete, pale red-brown, 4.2-5.8 mm thick, 3-sheathed; sheaths cylindrical, clasping stem, membranous, 16.2-43.4 × 4.5-8.7 mm. Inflorescence racemose, 2.9-9.6 cm long, 4- to 10-flowered; floral bracts oblong-lanceolate, 10.5-29.8 × 3.0-11.1 mm, apex acuminate, pale yellow; pedicel and ovary bright yellow,13.8-22.9 mm long, glabrous; sepals yellow, obovate elliptic, dorsal sepals 13.5-17.2 × 4.8-6.5 mm, obtuse; lateral sepals 16.3-18.6 × 5.9-6.7 mm, obtuse; petals yellow, narrowly elliptic, 15.5-19.7 × 6.0-6.5 mm, acute; labellum 3-lobed, with 3 pairs of purple-red stripes on side lobes and purple-red spots on middle lobe; side lobes erect, ivory-white, slightly clasping the column, subsquare, 4.5-5.6 × 5.3-6.2 mm; mid-lobe oblong, 7.8-10.2 × 6.1-7.8 mm, apex acute to obtuse; labellum with two sacs at the base and a fleshy callus centrally, indistinctive Y-shaped (in the transition to “T-shape”), with 3 auricles on the apex, each of which has 1 purple-red spot at the front; callus extending from the base of disc to the base of mid-lobe, triangular at the base of mid-lobe, fleshy, ca. 3.1 mm wide, 0.25 m long, narrows into a raised band when extended, ca. 1.5 mm wide, 0.4 mm long, with sparse purple-red spots; column cream colored, straight, semi-cylindrical, narrow wings on the side, 4.9-6.3 mm long, 2.9 mm wide, footless; stigma concave, triangular, terminal; anther cap ellipsoid, ca. 1.3 mm in diameter; pollinia four, in two pairs, narrowly elliptic, granular-farinaceous, composed of friable massulae, each pair containing two pollinia equal in size with a thick caudicle attached to a common subsquare viscidium, ca. 0.5 mm in diameter. Capsule purple red, fusiform, 3 evident banded ridges, 37.3-46.8 mm long, 8.9-10.1 mm thick. Seeds light dark brown, cylindrical, 1.3 × 0.3 mm, fleshy, honeycombed stripes on the seed coat surface.

Distribution and habitat.

Danxiaorchis mangdangshanensis is only found in Mangdangshan National Nature Reserve, Fujian, China (Fig. 6 ), where it grows at the margin of mid-subtropical evergreen broad-leaved forest, beside a canal near a Musa balbisiana forest. Many other plants grow in the surrounding habitat, whose tree layer includes Castanopsis fargesii Franch. ( Fagaceae ), C. fissa (Champion ex Bentham) Rehder et E. H. Wilson ( Fagaceae ), and Vernicia montana Lour. ( Euphorbiaceae ); the shrub layer includes Ficus erecta Thunb. ( Moraceae ), F. hirta Vahl ( Moraceae ), Maesa japonica (Thunb.) Moritzi. ex Zoll. ( Primulaceae ), Callicarpa kochiana Makino ( Lamiaceae ), and Aucuba chinensis Benth. ( Garryaceae ); the vegetation layer includes Angiopteris fokiensis Hieron. ( Marattiaceae ), Viola diffusa Ging. ( Violaceae ), Mazus fukienensis Tsoong ( Mazaceae ), Gynostemma pentaphyllum (Thunb.) Makino ( Cucurbitaceae ), Iris japonica Thunb. ( Iridaceae ), Musa balbisiana Colla ( Musaceae ), and Miscanthus floridulus (Lab.) Warb. ex Schum et Laut. ( Poaceae ); the interlayer plants include Fissistigma oldhamii (Hemsl.) Merr. ( Annonaceae ), and Stauntonia obovatifoliola Hayata subsp. urophylla (Hand.-Mazz.) H.N.Qin ( Lardizabalaceae ).

Phenology.

Flowering was observed from mid-April to early May, and fruiting from mid-May to mid-June.

Etymology.

The Mang dang shan dang xia lang (茫荡山丹霞兰).The epithet mangdangshanensis (茫荡山) refers to Mangdangshan Mountain, Mangdangshan National Nature Reserve, Fujian Province where this new species was found.

Conservation status.

During our fieldwork in 2022, three populations of about 14 plants of the new species were found in Mangdangshan National Nature Reserve, Fujian Province, China. And hence, we suggest its placement in the Data Deficient category of IUCN (2022). According to the Updated List of National Key Protected Wild Plants (Decree No. 15) by the country’s State Forestry and Grassland Administration and the Ministry of Agriculture and Rural Affairs, Danxiaorchis are classified in the national secondary protection list. The new recorded genus should also be included on the national secondary protection list during the upcoming revision process.

Characteristics of the Danxiaorchis mangdangshanensis plastome

The highly reduced plastid genome of Danxiaorchis mangdangshanensis still has a quadripartite structure and is 85,273 bp with a large single-copy (LSC) region of 42,605 bp separated from a small single-copy (SSC) region of 18,766 bp by two inverted repeat regions (IRs), each of 11,951 bp (Fig. 7 ). A total of 56 unique genes were identified in the plastome and it contains 32 protein-coding genes, 20 tRNAs, and four rRNAs. A total of seven genes were duplicated in the IR regions, including rpl22, rps19, trnH-GUG, rpl2, rpl23, trnI-CAU, ycf2 (Table 2 ). The total GC content of the plastome is 34.40%. Two inversions were detected in the plastome of D. mangdangshanensis (Suppl. material 1: Fig. S1), which are also reported for D. singchiana ( Li et al. 2020). The annotated plastome was deposited in GenBank (accession number OP122564).

Figures

Figure 3. Danxiaorchis mangdangshanensis Q. S. Huang, Miao Zhang, B. Hua Chen & Wang Wu, sp. nov. A flowering and habitat (photographed by Wang Wu) B front view of a flower C-a dorsal sepal C-b lateral sepals C-c petals C-d labellum D gynostemium and labellum, front view, showing three purple-red spots (white arrows) on the Y-shaped callus (red arrows) E gynostemium and labellum, side view, showing three auricles (red arrows) F labellum, showing remarkable striped appendage G gynostemium, showing narrow wings on the both sides (red arrows) H cross section of labellum, showing indistinct Y-shaped callus (red arrows) I anther cap J pollinarium, front view, showing pollinia 4 in 2 pairs. Scale bars: 5 mm (B); 1 cm (C); 4 mm (D); 5 mm (E); 4 mm (F); 1 mm (G); 4 mm (H); 500 μm (I, J).

Figure 4. Danxiaorchis mangdangshanensis Q. S. Huang, Miao Zhang, B. Hua Chen & Wang Wu, sp. nov. A fruit-bearing plant (photographed by Wang Wu) B infructescence and rhizome C longitudinal section of immature capsule D mature capsule, showing mature seeds (red arrow) E mature seeds. Scale bars: 1 cm (B, C); 1 mm (D, E).

Figure 5. Danxiaorchis mangdangshanensis Q. S. Huang, Miao Zhang, B. Hua Chen & Wang Wu, sp. nov. A flowering plant B flower, front view C dissection of a flower, showing dorsal sepal, petal, lateral sepal D gynostemium and labellum, front view E gynostemium and labellum, side view F labellum G gynostemium H anther cap I pollinarium J immature capsule K mature seeds. Scale bars: 1.0 cm (A, B, C, J); 0.5 cm (D-F); 0.2 cm (G); 1.0 mm (H, I, K).

Figure 6. Distribution of Danxiaorchis mangdangshanensis, D. singchiana, D. yangii in China. Legend: (red star) D. mangdangshanensis, (black circle) D. singchiana, (black triangle) D. yangii.

Figure 7. Circular gene map of the plastid genome of Danxiaorchis mangdangshanensis. Genes inside the circle are transcribed clockwise, while those drawn outside are transcribed counterclockwise. Genes are color-coded according to their functional groups. The circle inside the GC content graph marks the 50 % threshold.