Gastrodia pushparaga Gopallawa, Perera & Madola, 2023

Gopallawa, Bhathiya, Perera, Amila, Madola, Indrakheela, Yakandawala, Deepthi, Kumar, Pankaj, Jayawickrama, Harsha & Chase, Mark W., 2023, Gastrodia pushparaga (Orchidaceae, Epidendroideae, Gastrodieae), a new species from Sri Lanka, Phytotaxa 587 (2), pp. 193-199 : 195-197

Gastrodia pushparaga Gopallawa, Perera & Madola , sp. nov. ( Figs 1–3 )

Type:— SRI LANKA. Sabaragamuwa Province: Rathnapura District, Walankanda Forest Reserve , 612 m a.s.l., 1 Apr 2021, Gopallawa & Perera BGAP-001 B ( K); Gopallawa & Perera BGAP 001 - A (holotype: PDA)

Gastrodia pushparaga is similar to the Taiwanese endemic, G. sui , but the former can be differentiated from latter on the basis of larger flowers with longer perianth tube (length> 1.5 cm vs. 1.2 cm), inner surface of perianth tube smooth (lacking a callus vs. a red callus on each lobe), lip white (vs. reddish brown), two round calli at the base of the epichile (vs. on the hypochile) and broadly ovate to triangular column wings (vs. narrowly linear). It is like G. uraiensis , from Taiwan and Guangxi, China, but this species again lacks the column wings of the new species and its perianth tube is much less swollen and externally verrucose (versus glabrous in the new species).

Leafless herbs up to 15 cm long, aerial part 7–8 cm tall, underground, swollen rhizome up to 6 cm long, 1.7–1.9 cm in diameter, reddish brown, marked with nodular rings spaced 0.3–0.6 cm apart along its length, each ring with multiple triangular scales, scales 4.0–6.0 mm long, 1.5–2.0 mm wide, acuminate. Stem terete, 5.0–6.0 cm long, 0.3–0.4 cm wide, red, glabrous, multi-noded, each node with a sterile bract, bract broadly triangular, 0.4–0.7 × 0.6–0.8 cm, acute, translucent greyish brown. Inflorescence a raceme, 2–4-flowered, peduncle 2.0– 2.2 cm long, 0.2–0.4 cm in diameter, same color as stem. Floral bracts triangular, 0.5–0.7 × 0.4–0.5 cm, acute, papery, dark brown. Flowers facing upwards, petals and sepals fused to form a perianth tube, pedicellate, pedicel terete, 6.0–7.0 mm long, 0.7–0.8 mm in diameter, reddish brown, glabrous; ovary 3-ribbed, 4.0–5.0 mm long, 1.5–2.0 mm in diameter, reddish brown, glabrous. Perianth tube 1.7–1.9 cm long, 1.0– 1.1 cm in diameter at the apex, up to 1.4 cm wide at the swollen base, open only at the apex, opened part 2.1–2.3 cm wide, outer surface mixture of yellow and salmon pink, inner surface yellow towards apex, white below, with a white band under the labellum on the fused lateral sepals separating two broad red bands on each side, each intersected by two orange bands longitudinally, perianth tube slightly verrucose towards apex, smooth in lower part, glabrous throughout. Dorsal sepal broadly obovate, 1.2–1.3 × 0.5–0.6 cm, acute, apical half yellowish brown, lower half white, apex slightly reverted backwards, lateral sepals obliquely ovate, 1.4–1.5 × 0.8–0.9 cm, acute, longitudinal white band along the connate margin followed by broad dark red band on each side and a white band, yellowish towards the apex, petals obovate, 0.5–0.6 × 0.3 cm, obtuse, yellow. Lip 0.9–1.0 × 0.5–0.6 cm wide with a longitudinal ridge underneath running from base to the apex, distinctly divided into hypochile and epichile; hypochile a narrow rectangular appendage connecting epichile to the column base, 0.9–1.0 × 1.0– 1.5 mm, white, epichile ovate, 0.9 × 0.5–0.6 cm, acute, white towards base with dark grey veins, yellowish towards apex, with 2 diverging lamellae towards the centre, 1.5–2.0 mm long, 0.5 mm high, a pair of globose calli on each side of the base, 0.5 mm in diameter. Column broadly ovate including the wings, 0.7–0.8 cm long, up to 0.6 cm wide, with a tapering base, with 2 protruding claw-like stelidia on the front, 0.6–0.8 mm long, 0.4–0.5 mm in diameter, third finger-like wing on the back of the rostellum, almost 1 mm broad and slightly shorter than stelidia, tapering base almost terete, up to 1.0 mm long, 2.5 mm wide, stigma situated on the top of this tapering base, convex, anther cap almost round in outline, 1.2–1.4 mm in diameter, 0.7–0.8 mm deep. Fruit a capsule, clavate, 1.2–1.4 cm long, 0.6–0.8 mm in diameter at dehiscence, on an elongate pedicel of variable length, 7–12 cm.

Phenology:— Flowering March–April; fruiting April–June.

Etymology:— Referring to the yellow sapphire, locally known as pushparaga , in the Rathnapura district, famous for its gems. The flower colour is similar to that of yellow sapphire, where a high-quality yellow sapphire has a red tint, similar to the flower. This epithet is to be treated as a noun in apposition.

Notes on habitat:— Within all observed populations, individuals of Gastrodia pushparaga grow in the mixed dipterocarp dominated forests dominated by Dipterocarpus hispidus Thwaites (1858: 33) , Shorea cordifolia ( Thwaites 1858: 35) Ashton (1973: 362) , Shorea trapezifolia ( Thwaites 1858: 35) Ashton (1972: 363) and Vateria copallifera ( Retzius 1786: iv 27) Alston in Trimen (1931: 26) ( Dipterocarpaceae ) and other species such as Bhesa ceylanica (Arnott in Thwaites 1858: 72) Hou (1958: 151) (Centroplaccaceae), Humboldtia laurifolia Vahl (1794: 106 (Fabaceae) , Agrostistachys coriacea Alston in Trimen (1931: 265 (Euphobiaceae) and Mesua ferrea Linnaeus (1753: 515 ( Clusiaceae ). All populations grow in dense leaf litter enriched with decaying plant material, predominantly in shady areas, some of which have rocky substrates on somewhat sloping ground. Plants were found at 400–650 m elevation.

Distribution:— So far restricted to the Rathnapura District, Sabaragamuwa Province, Sri Lanka ( Fig. 4 ).

Conservation assessment:— Based on two years of rigorous surveys, 22 subpopulations of Gastrodia pushparaga were found to occur at six distinct sites in the wet zone of Sri Lanka at Walankanda (five subpopulations each in one hectare plots, with 20–50 mature individuals at three sites and 20–30 mature individuals at other two), Panapola (ten subpopulations of 20–30 mature individuals each spread over an area of three hectares), Weddagala (one subpopulation with up to 15 mature individuals) and Kalawana (one subpopulation with up to 15 mature individuals in Sabaragamuwa Province) and at Delgoda (five scattered subpopulations with up to ten mature individuals) in Sabaragamuwa Province. The overall population size is estimated to be around 400 mature individuals (<500 mature individuals). All these subpopulations generate an EOO of 114 km 2 and an AOO of 20 km 2 using GeoCAT ( Moat 2007). At these sites, the plants occur in mixed dipterocarp forests, and at least, at two sites, Panapola and Kalawana, the habitat is fragmented. The species is not known to face any threat and hence the number of locations is zero. Overall, following IUCN (2019), the new species can be assessed as vulnerable (VU D1) owing to its small population size of <500 mature individuals.

Additional specimens examined:— Walankanda Forest Reserve , 588 m a.s.l., 5 Mar 2022, Gopallawa & Perera BGAP 002 (spirit PDA) ; Walankanda Forest Reserve , 612 m a.s.l., 1 Apr 2021, Gopallawa & Perera BGAP-001 B ( K); Walankanda Forest Reserve , 588 m a.s.l., 5 Mar 2022, Gopallawa & Perera BGAP 003 (spirit PDA).

Figures

FIGURE 1. Gastrodia pushparaga. A.–B. Plant in habitat. C. Whole plant. D.–E. Close-up of flower (top view). F. Inflorescence. G. Stem. H. Flower (front view). I. Flower (back view). J. Flower (view from below). K. Perianth tube (opened). L. Bud and open flower. M.–N. Flower (side view). O. Mature fruit with seeds. P. Immature fruit. Q. Column and labellum (ventral and dorsal views). R. Column and labellum (side views). S. Column and labellum (view from above). T. Epichile (dorsal view). U. Column with ovary (dorsal view). V. Rhizome. Scale bars = 1 cm. Photographs by Bhathiya Gopallawa.

FIGURE 2. The typical habitat of Gastrodia pushparaga in shaded terrain covered with thick leaf litter in mixed dipterocarp community, lowland rain forest, Walankanda Forest Reserve. Photograph by Amila Perera.

FIGURE 3. Gastrodia pushparaga.A. Habit of the flowering plant. B.–C. Flower (side view). D. Flower (front view). E. Epichile (dorsal view). F. Column with ovary (dorsal view). G. Mature fruit with seeds. Illustration by Indrakheela Madola.

FIGURE 4. Map of Sri Lanka indicating the locations of Gastrodia pushparaga in the wet zone.