Gastrodia huapingensis X.Y.Huang, A.Q.Hu & Yan Liu, 2015

Huang, Xin-Yi, Hu, Ai-Qun, Hsu, Tian-Chuan & Liu, Yan, 2015, Gastrodia huapingensis (Orchidaceae: Epidendroideae: Gastrodieae): a remarkable new mycoheterotrophic orchid with dimorphic columns from China, Phytotaxa 222 (4), pp. 290-294 : 290-292

Gastrodia huapingensis X.Y.Huang, A.Q.Hu & Yan Liu , sp. nov. ( Figs. 1 , 2 )

Type:— CHINA. Guangxi: Guilin City, Huaping National Nature Reserve , in the bamboo forest, elevation ca. 1,650 m, 26 August 2014, Longsheng expedition team of Chinese traditional medicine 450328140826139 (holotype: IBK!; isotypes: IBK! and PE!) .

Diagnosis: — Gastrodia huapingensis is similar to G. major Averyanov and G. punctata Averyanov (both in Averyanov & Efimov 2006), but it is distinct from these two in its ovate lip with truncate apex, undulate to erose epichile and dimorphic (extended or incurved) columns.

Terrestrial mycoheterotrophic leafless herbs. Roots few, up to 20 cm long, ca. 1 mm in diameter, at the apex of rhizome, branched. Rhizome tuberous, fusiform, subterete, 10–35 mm long, 5–10 mm in diameter, grayish brown, covered with dense unicellular hairs. Inflorescence erect, terminal, 1–10-flowered, glabrous, peduncle 10–40 cm long, 0.02–0.03 cm in diameter, with 4–6 sterile bracts; sterile bracts ovate, yellowish brown, ca. 5 mm long. Pedicel and ovary ca. 10 mm long, pedicel slightly curved, ovary ca. 2.5 mm in diameter. Flowers pointing slightly downwards, widely opening, bell-shaped, resupinate, grayish brown. Sepals and petals forming a perianth tube, 10–15 mm long, 6–7mm in diameter, pale brown; sepals 10–15 mm long, connate for 3/4 length and adnate for 4/5 their length with the petals, grayish brown, glabrous, free portion of dorsal sepal ovate, margin slightly undulate, ca. 5 mm long, 3 mm wide, free portions of lateral sepals spreading, triangular, margin slightly undulate, ca. 5 × 5 mm, free portions of petals ovate, ca. 3.0 × 2.5 mm, margin slightly erose, apex obtuse, base contracted, slightly clawed. Lip adnate to column foot, ovate with truncate apex, 5 × 3 mm, pale yellowish brown, hypochile grayish brow, with two reddish brown, globular calli, epichile ovate, margin undulate to erose and finely undulate in apical portion, disc with 5 longitudinal ridges, the central two much longer and more prominent. Column extended or incurved, the former 4.5 × 2.0 mm, straight, slightly bending in the middle, flat, apex broader, stigma located at the base; the incurved column ca. 1.5 mm long, ca. 1.5 mm in diameter, apex broader due to bending of the column, the anther touching the stigma, column foot well developed in both cases. Capsule erect, narrowly cylindric, 1.0– 1.5 cm long, 0.03–0.04 cm in diameter, pedicel elongating to 3.5–5.0 cm in fruit.

Additional specimens examined:— Gastrodia huapingensis : CHINA. Guangxi: Guilin City, Huaping National Nature Reserve, elev. 1,670 m, 29 August 2014, Longsheng expedition team of Chinese traditional medicine 450328140829007 (IBK!). Gastrodia major : VIETNAM. Dak Lak Prov: Krong Bong Distr, 28 October 2005, Averyanov, Thao, Vinh, HLF 5444 (holotype, HN, photo!). Gastrodia punctata : VIETNAM. Lam Dong Prov: Lac Duong Distr, 15 October 2005, Averyanov, Loc, Regalado et al., HLF 5237a (holotype, HN, photo!).

Distribution and habitat:— Gastrodia huapingensis was discovered in the Huaping National Nature Reserve, northeastern Guangxi. The population was scattered in the mixed subtropical evergreen broad-leaved forest, 1,600 – 1,700 m, in which bamboos were dominant. Population size was small. No more than 20 plants were found flowering or fruiting at the time of observation in 2014. Growing in shaded and damp humus and amongst fallen bamboo leaves, this mycoheterotrophic orchid was difficult to detect due to its grayish brown stem and flowers.

Phenology:— Gastrodia huapingensis flowers late July to August and fruits September to October.

Etymology:— The specific epithet is derived from the type locality, Huaping National Nature Reserve in northeastern Guangxi, China.

Taxonomic notes:— Gastrodia huapingensis is morphologically similar to G. major and G. punctate ; they share a many-flowered inflorescence, bell-shaped perianth and lip with several longitudinal ridges. However, it is not difficult to distinguish G. huapingensis from the other two by its ovate lip with truncate apex, undulate to erose epichile and dimorphic (straight and incurved) columns. More detailed comparisons between Gastrodia huapingensis and G. major , G. punctata are presented in Table 1.

The new species is remarkable for its dimorphic columns found in different flowers on the many-flowered inflorescence, which is documented for the first time in the genus Gastrodia . In flowers with an extended column, the male part (anther) is distant from the female part (anther) and a pollinator-dependent pollination system is predicted. In flowers with an incurved column, the bent column enables the anther to touch the stigma located at the base of the column, which most likely leads to self-pollination. This automatic self-pollination may act as an efficient reproductive assurance in a pollinator-scarce habitat. During our field observations, no insect was observed to visit the flowers. However, high natural fruit-set (95%, n=5) was observed in Gastrodia huapingensis . We hypothesise that the incurved column may be associated with a potential mechanism of delayed automatic self-pollination whereas the straight column may occur at the early stages of anthesis, providing the potential for cross pollination. We dissected flowers on specimens to check the distribution of the incurved column along the inflorescence. We found that both column types occurred on the same inflorescence, and the incurved ones were randomly distributed along the inflorescence. Due to limited specimens (n=5) with limited flowers (3–5 on each) in this study, the timing of the incurving was unable to be confirmed. More field observations of column development in a single flower and the proportion of flowers with incurved column on the whole inflorescence of this species are needed.

Figures

FIGURE 1. Gastrodia huapingensis. A. Habit. B. Inflorescence.C. Immature fruit.D. Mature fruit. E. Flower (front view).F. Flower (side view). G. Perianth tube, expanded and flattened. H–I. Lip. J. Lip and incurved column (side view). K. Lip and normal column (side view). L. Rhizome (with roots removed). Scale bars: B–D. 1.5 cm; E. 2 mm; F–G. 5 mm; H–K. 2 mm; L. 1 cm.

FIGURE 2. Gastrodia huapingensis. A. Habit. B. Mature fruit. C. Flower (front view). D. Flower (side view,). E. Perianth tube, expanded and flattened. F–G. Lip. H. Lip and incurved column (side view). I. Lip and normal column (side view).