Gastrodia solomonensis T.C.Hsu, 2016

Hsu, Tian-Chuan, Fanerii, Moffat, Yang, Tsung-Yu Aleck, Pitisopa, Fred & Li, Chia-Wei, 2016, Gastrodia isabelensis and G. solomonensis (Gastrodieae, Epidendroideae, Orchidaceae): two new species representing a new generic record in the Solomon Islands, Phytotaxa 270 (2), pp. 137-145 : 141-144

Gastrodia solomonensis T.C.Hsu , sp. nov. ( Figs. 3–4 )

Diagnosis: — Gastrodia solomonensis is close to G. queenslandica ( Dockrill 1964: 6) but distinguished by having much longer (22–28 vs. 8–12 mm) perianth tubes, larger (7–9 × 4.5–5.5 vs. 4.5–5.5 × 2.5–3.0 mm) lips with elliptic (vs. ovate) mesochiles and wider (3.5–4.5 vs. ca. 3 mm) columns.

Type: — SOLOMON ISLANDS. Western : Kolombangara Island , Imbu Rano Lodge to Patu Kolo Hut, 400–600 m, 13 October 2012, T. C.Hsu et al. SITW00764 (holotype: BSIP!; isotypes: TAIF! [sheet no. 421455], image available at http://taif.tfri.gov.tw/search_ spec.php?SpcmID=325160&DupID=1&SeriID=1&DetID=441994; TNM! [sheet no. BS01936], image available at http://siflora. nmns.edu.tw/specimen/ SITW00764 -TNM-001/) .

Morphology: — Herbs perennial, terrestrial, leafless, achlorophyllous. Roots few, slender, often extending from rhizome apex during anthesis. Rhizome tuberous, fusiform, 4–10 cm long, 4–7 mm in diameter, dark brown, ±villous, scaly; scales verticillate, lanceolate, 1–3 mm long. Inflorescence erect, 1(–2)-flowered; peduncle 4–8 cm long, ca. 2 mm in diameter, glabrous, dark brown; sterile bracts 3–4, sheath-like, membranous, translucent, 3–5 mm long. Bracts membranous, glabrous, ovate, brown, apex acute, 6–8 × 4–6 mm. Pedicel and ovary 8–10 mm long, slightly verruculose. Flowers ascending, not widely opening. Perianth tube 22–28 × 15–20 mm, elliptic in top view, very fleshy, spongy, 5-lobed, with sepals fused for ca. 1/2 length with petals and lateral sepals fused for ca. 3/5 length with each other; abaxially pale reddish near base, yellowish brown toward apex, slightly keeled, distinctly verruculose; abaxially whitish near base, pale orange-red toward apex, with 2 large, orange-yellow, rugose calli. Lobes of dorsal and lateral sepals similar, ovate-deltoid, 10–14 × 7–9 mm, concave, apices acute, margins entire. Lobes of petals ovate, pale orange-red, 4–5 × 3.5–4.5 mm, bases slightly contracted, apices acute, margin slightly crispate. Lip adnate to distal part of column-foot, free from perianth tube, subentire, rhombic-elliptic, 7–9 × 4.5–5.5 mm, tripartite; hypochile ca. 1.5 mm long, with two transversely crescent, sessile, creamy yellow, nectared calli; mesochile elliptic, very pale reddish, glabrous, nearly flat or with 2 indistinct ridges close to midrib; epichile ovate-orbicular, orange-red, ca. 2 mm long and wide, with 2 prominent, orange-red, ca. 2 mm long keels. Column semicylindrical, white, 7–8 × 3.5–4.0 mm, ventrally canaliculate; column-foot short but well developed; column wings prominent, the tips about as high as anther; rostellum well developed, membranous; stigma basal, shield-shaped; anther ovate-hemispheric, ca. 2.5 × 1.8 mm; pollinia 2, pale orange-yellow, sectile; viscidium minute. Capsule erect, ellipsoid, pale reddish brown, 25–40 mm long, 5–8 mm in diameter, verruculose; fruiting pedicel elongate after pollinated, up to 8–30 cm long. Seeds fusiform, ca. 2 mm long.

Distribution and habitat:— Gastrodia solomonensis is endemic to the Solomon Islands, and so far it is only recorded in Kolombangara Island and Nggatokae Island of Western Province. Wild populations are found growing among deep leaf litter in rain forests at 300–600 m elevation.

Phenology:— Gastrodia solomonensis flowers from September to October and fruits from October to November.

Conservation:— Three populations of Gastrodia solomonensis are so far located: Southern Kolombangara (ca. 100 mature individuals recorded), northern Kolombangara (ca. 10 mature individuals recorded) and Nggatokae (ca. 10 mature individuals recorded). The montane forest of Kolombangara are now protected by a non-governmental organization namely Kolombangara Island Biodiversity Consefvation Association (KIBCA), and no obvious threat is predicted. The habitat in Nggatokae is now protected by the landowners in Mbiche village but still under the threat of logging. Judging from these facts, G. solomonensis is considered “Near Threatened” according to the IUCN Red List Categories and Criteria ( IUCN 2012).

Etymology:— Gastrodia solomonensis is named for the Solomon Islands since it is the first Gastrodia species discovered in this country.

Additional specimens examined:— SOLOMON ISLANDS. Western : Kolombangara Island , Imbu Rano Lodge to Patu Kolo Hut, 500–600 m, 16 October 2012, Hsu et al. SITW01081 ( BSIP!, TAIF!, TNM!) ; Kolombangara Island , Imbu Rano Lodge to Patu Kolo Hut, 400–600 m, 13 October 2013, Hsu et al. SITW04203 ( BSIP!, TAIF!, TNM!) ; Kolombangara Island , Poitete Village to camp 3, 300–500 m, 26 November 2013, Hsu & Fanerii SITW04728 ( BSIP!, TNM!) ; Nggatokae Island , Mbiche Village to Mt. Mariu, 300–600 m, 8 October 2013, Hsu et al. SITW04089 ( TNM!) .

Taxonomic remarks:— Gastrodia solomonensis is remarkable by its 22–28 × 15–20 mm perianth tube, possibly the largest in the genus, and elliptic mesochile of lip. Its inflorescences are almost always 1-flowered. Only one plant with 2-flowered inflorescence were ever recorded among the ca. 100 flowering and fruiting individuals so far observed.

Figures

FIGURE 3. Gastrodia solomonensis T.C.Hsu (A & C–J based on SITW00764; B & K based on SITW01081). A–B. Habitat and habits. C–E. Flower (C, top view; D, side view; E, front view). F. Expanded perianth tube and lip, abaxial view. G. Lip. H. Lip and column, side view. I–J. Column (I, top view; J, bottom view). K. Capsule. Scale bars: A–K = 1 cm. Photographs by T.C.Hsu.

FIGURE 4. Gastrodia solomonensis T.C.Hsu (based on SITW00764). A. Habit. B–E. Flower (B, top view; C, side view; D, front view; E, bottom view). F. Expanded perianth tube, abaxial view. G. Lip and column, side view. H. Lip. I–K. Column (I, top view; J, side view; K, bottom view). L–M.Anther cap (L, top view; M, bottom view). N. Pollinia. Illustrated by C.W.Lin.