Gastrodia microchila Hroneš sp. nov.

Figs 1, 2, 3

Type.

Brunei Darussalam • Belait district: Labi village, northern slopes of Bukit Telingan, mixed dipterocarp forest ca. 1.8 km E of primary school in Kampung Rampayoh, 4.37672°N, 114.47339°E, 200 m alt., 25 Nov 2024, Hroneš 2024 / 4 (holotype: BRUN B 045 889).

Diagnosis.

Gastrodia microchila is similar to G. holttumii Carr from Peninsular Malaysia but differs by narrower cylindrical rhizome without distinct nodes (vs. robust, distinctly noded), flowers 8.5–9.0 mm wide, narrowly open (vs. 9.0–11.0 mm wide, widely open), free part of lateral and dorsal sepals oblong triangular to broadly triangular, up to 4.5 × 5.0 mm (vs. elliptic to oblong elliptic, 6.0–7.0 × 3.0–5.0 mm), free part of petals indistinct, ca. 0.7 × 0.6 mm, elliptic (vs. 1.0–2.0 × 0.7–1.0 mm, ovate), hypochile 2.0 × 2.0 mm, broadly oblong-orbicular (vs. 2.0 × 1.5 mm, oblong-ovate) and stelidia longer than anther cap (vs. subequal to anther cap).

Description.

Terrestrial, achlorophyllous herb, 16–21 cm tall. Rhizome ca. 50 mm long, 3–6 mm in diameter, tuberous, fleshy, cylindrical, without distinct nodes, densely covered by filiform scales. Stem 128.5–165.0 mm long, 1.8–2.2 mm in diameter, with 4–6 nodes, ± erect, indistinctly ridged, covered by low blunt verrucae, whitish brown, pale greyish brown to beige. Leaves 2.7–5.5 mm long, 2.5–3 mm wide at base, scale-like, broadly triangular, basally clasping, tip acute to erose, brown. Bracts subtenting base of each pedicel 2, unequal in size; longer one 4.0– 4.5 mm long and 2.8–3.4 mm wide, broadly triangular, clasping basally, keeled, persistent, covered by low blunt verrucae, brown; shorter one 3.7–4.6 mm long, ca. 0.5 mm wide at base, 1.5–1.8 mm wide in the middle part, stipitate ovate to stipitate triangular with tapering tip, keeled, caducous in lower flowers. Inflorescence loose, 2–4 flowered; rhachis 8.5–10.5 mm long. Pedicel 2.5–5.3 mm long, 1.0– 1.4 mm in diameter, elongating to 12.5–100.0 mm in fruit, with 6 distinct ribs, becoming smoother in fruit, greyish pink to pinkish orange. Flower (excluding ovary) 13.0–15.0 mm long, 8.5–9.0 mm wide, spreading almost horizontally, narrowly open, with sepals and petals basally fused, forming a five-lobed, tubular campanulate perianth tube; flower bud pinkish orange. Sepals externally pale pinkish orange, covered by low blunt verrucae (more distinct in young flowers), internally pinkish orange at base and whitish orange to beige apically. Lateral and dorsal sepals connate into synsepalum for ca. 2 / 3 of their length, lateral sepals connate for up to 1 / 2 of their length, connation perfect for basal 3–4 mm, additional 3–5 mm connate imperfectly, leaving a conspicuous furrow on the surface of flower; free portion 4.0–4.5 × 4.5–5.0 mm, oblong triangular, cucullate, blunt at apex, with irregular translucent margin, internally with beige-orange to deep orange-pink, cushion-like smooth tissue covering most of the sepal space. Free portion of dorsal sepal 5.0 × 5.0 mm, broadly triangular, blunt and shortly cucullate at apex, with irregular translucent margin. Free portion of petals indistinct, ca. 0.7 × 0.6 mm, elliptic, whitish orange to beige, almost translucent. Lip ca. 3.0 × 2.0 mm, adnate to base of column, greyish pink to beige; hypochile ca. 2.0 × 2.0 mm, thick and fleshy, almost flat, broadly oblong-orbicular; epichile 1.0 × 0.8 mm, oblong to almost rectangular with wide obtuse apex bent downwards, orange to reddish brown; keel ca. 0.4 mm wide, positioned at the transition of hypochile and epichile, hypochile part beige, epichile part reddish brown, with margins raised into two low ridges which have the tallest part at the transition between hypochile and epichile; calli ca. 0.2 × 0.2 mm, ± globose, pale orange-brown. Column ca. 3.0 × 1.9 mm, straight, oblong to rectangular, canaliculate, winged, without distinct rostellum, central part beige, wings slightly ventricose, beige, basally pale pinkish orange; stelidia ca. 0.8 mm long, terete, elliptic-triangular, obtuse, beige, slightly exceeding anther; anther cap ca. 0.6 × 0.9 mm, rectangular-ovate; pollinia not seen; stigma not seen. Ovary 2.3–5.0 × 1.8–2.6 mm, attached at an angle to pedicel, obconical, bluntly trilobed in intersection, slightly ventricose, with 3 high and 3 low ribs alternating to each other, covered by low blunt verrucae, greyish pink basally, greyish brown apically. Capsule 13.2–15.6 × 4.0– 5.1 mm, cylindrical-fusiform, greyish pink in most part, brown apically.

Distribution and habitat.

Endemic to Brunei Darussalam. So far known only from its type locality in the Belait District. It grows in mixed dipterocarp forest on shady and humid slopes near the small streams. The forest was probably lightly logged in the past.

Etymology.

The name is derived from the Latin micro - = small and - chilum = lip, referring to the size of the lip, which is among the smallest in Gastrodia species in western Malesia.

Conservation status.

The species is currently known from a single small population spanning less than 500 m 2. Fewer than ten individuals were observed at the site. The population is located in currently unprotected forest. Consequently, any random natural or human-induced event could destroy the site and the entire population. Therefore, we propose to preliminarily treat G. microchila as critically endangered (CR) based on the B 2 ab (iv) + D criteria.