Gentiana betongensis (Gentianaceae), a new species from tropical montane sphagnum bog in Peninsular Thailand Author Wai, Jarearnsak Sae Division of Biological Science, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla 90110, Thailand. jarearnsak.s@psu.ac.th text Phytotaxa 2024 2024-01-03 633 1 60 67 http://dx.doi.org/10.11646/phytotaxa.633.1.7 journal article 10.11646/phytotaxa.633.1.7 1179-3163 Gentiana betongensis J. Wai , sp. nov. ( Figs. 2–3 ). TYPE :— THAILAND . Yala Province : Betong District, High Plateau, 5°58’25.7”N , 101°26’30.7”E , 1500 m elev., 24 May 2022 , J . Wai 2789 ( holotype PSU !, isotype BKF !). Diagnosis: Gentiana betongensis is morphologically most similar to G. malayana in having erect, simple, few-branched stems, but differs in having smaller flowers (ca. 9 mm long vs. ca. 12.7 mm long), triangular-ovate, acute corolla lobes (vs. subspathulate, rounded corolla lobes), and recurved and coiled stigma lobes (vs. not coiled stigma lobes). It is also similar to G. borneensis but can be distinguished by its habit (erect, simple or few-branched herb vs. caespitose, much-branched herb), unlobed plicae (vs. bilobed), and recurved and coiled stigma lobes (vs. not coiled stigma lobes). A detailed comparison of G. betongensis , G. malayana , and G. borneensis is presented in Table 1 . TABLE 1. Comparison of selected morphological characters of Gentiana betongensis , G. malayana and G. borneensis . Information on the morphological characters of G. malayana and G. borneensis was obtained from Ridley (1908) and Hooker (1883) .

Characters	G. betongensis	G. malayana	G. borneensis
Stem	erect, simple or few-branched, 7–10	erect, simple or few-branched, 2.5–7.6	caespitose, much-branched, 2.5–5
cm high	cm high	cm high
Leaf length	10–28 mm long	6–12.7 mm long	6–8.5 mm long
Flower	ca. 9 mm long	ca. 12.7 mm long	ca. 8.5 mm long
Corolla lobes	triangular-ovate with acute apex	subspathulate with rounded apex	triangular-ovate with acute apex
Plicae	apex unlobed	apex unlobed	apex bilobed
Anther	oblong to oblong-lanceolate	narrowly hastate	hastate
Stigma lobes	recurved and coiled	not coiled	not coiled
Geographical	Peninsular Thailand	Peninsular Malaysia	Borneo
distribution

FIGURE 2 . Gentiana betongensis J. Wai. A. Habit. B. Leaves showing both adaxial (left) and abaxial (right) surfaces. C. Bracts. D. Flower, lateral view (left), top view (right). E. Dissected flowers. F. Calyx. G. Corolla opened showing epipetalous stamens. H. Pistil. I. Fruit, top view. J. Fruit with persistent calyx, corolla, style, and stigma lobes, side view. K. Seeds. All from J. Wai 2789 (PSU). Drawn by K. Singkam. FIGURE 3 . Photos of Gentiana betongensis J. Wai. A. Natural habitat. B. Habit. C. A whole plant with floral buds and fruits. D. Flower. Photographed by J. Sae Wai on 24 May 2022. Description:— Perennial herbs, 7–10 cm high. Stems erect, slender, terete, simple or with few flowering branches, dark purple, purplish green in basal portion, subglabrous, with scattered very minute papillae (seen under magnification); internodes up to 2 cm long. Root fibrous, linear-cylindrical, cream. Leaves 4–6 pairs, opposite decussate, sessile, forming sheath at base; sheath 1–2 mm long; blades rigid, slightly succulent, lanceolate, 1–2.8 × 0.4–0.9 cm , green or purplish, apex acute to apiculate, base attenuate, margin entire or subentire, minutely papillate along margin of leaf base; venation usually 1-veined, occasionally 3-veined, imperfect basal acrodromous; midrib shallowly grooved adaxially, prominent abaxially. Flowers solitary, in terminal clusters or sometimes axillary, ca. 9 mm long. Bracts opposite, linear-oblong, 9–15 × 0.5–0.8 mm , apex acute to apiculate, margin shortly ciliolate. Pedicels subsessile, 0.7– 1.1 mm long. Calyx membranous, cream or yellowish white, long-persistent; tube obconical, 2.5–2.75 mm long; lobes 5, subequal, narrowly triangular, 1.7–2.2 × 0.7–0.8 mm long, each lobe with a rib, apex long acuminate to apiculate, margin entire. Corolla outside cream tinged with purplish green, inside bluish purple, with yellowish corolla throat, long-persistent; tube campanulate, 7–7.5 mm long; lobes 5, triangular-ovate, 1.5–2 × 1–1.25 mm , apex acute; plicae triangular-ovate, 0.5–0.6 × 0.5–0.8 mm , apex acute or obtuse. Stamens 5, epipetalous, inserted ca. 2 mm above base of corolla tube, included; filaments filiform, slightly flattened, 2.5–3 mm long, creamy white; anthers basifixed, oblong to oblong-lanceolate, 0.9–1 mm long, cream or yellowish white. Pistil 2-carpellate, 6.5–7 mm long; ovary superior, 1-locular, oblong-oblanceolate, slightly flattened, winged, 3.5–4 mm long, ca. 1 mm wide, ca. 0.5 mm thick, shortly stalked, stalk to 1 mm long; style short, 0.5–0.8 mm long; stigma bifid, lobes recurved and coiled, longer than style, 2–3 mm in length. Capsule 2-valved, apical and septicidal dehiscence, oblong-oblanceolate, slightly flattened, winged, 13–14 mm long, 4.5–5 mm wide. Seeds numerous, ellipsoid, ca. 0.5 mm long; testa cells reticulate-rugose, brown. Distribution:— Peninsular Thailand . Known only from the type locality (Betong). Habitat and Ecology:— Terrestrial plant. This species was found growing in exposed areas, in montane sphagnum bog at ca. 1500 m alt. Phenology:— Flowering and fruiting were observed in May to June. Reproductive Biology:— Self-pollination (autogamy) was observed in this species even in the absence of pollinators. The open capsules of this species were found to be dispersed during rainfall by splash-cup dispersal mechanisms. GenBank accession number:— OP821985 (ITS), sequenced from J. Wai 2789 . Etymology:— The specific epithet “ betongensis ” refers to Betong District where this species has been found. Vernacular name:— Dok Rit Betong (ดอกหรีดเบตง). Proposed IUCN conservation assessment:— Critically Endangered ( CR ) under criteria B1 ab (iii, v) + B2 ab (iii, v) ; D. The known extent of occurrence ( EOO ) ( 4 km 2 ) is less than 100 km 2 and the known area of occupancy ( AOO ) ( 4 km 2 ) is less than 10 km 2 . This species is known only from the type locality near the Thai-Malay border and the total number of mature individuals observed is less than 10 individuals. In addition, the tropical montane bog in Betong District is at risk of habitat destruction by future road construction and inappropriate tourism developments. Therefore , this species is qualified as CR according to IUCN Red List Categories and Criteria guidelines Version 15.1 ( IUCN Standards and Petitions Committee 2022 ) .