Gymnostachyum calcicola Rafidah, 2024

Rafidah, Abdul Rahman, Ummul Nazrah, Abdul Rahman & Ong, Poh Teck, 2024, Gymnostachyum calcicola (Acanthaceae), a new species from limestone karst of Peninsular Malaysia, PhytoKeys 242, pp. 273-280 : 273-280

Gymnostachyum calcicola Rafidah sp. nov.

Figs 1 , 2 , 3

Diagnosis.

Unique among Peninsular Malaysian species of Gymnostachyum by having a racemose inflorescences occasionally lower axils with pairs of flowers and dichasium inflorescence with opposite branches. Gymnostachyum calcicola shows affinity with Gymnostachyum decurrens var. decurrens and var. robinsonii by its crowded rosette leaves at the base, however it is different in the inflorescences type.

Type.

Peninsular Malaysia. Kelantan: Chiku , FELDA Chiku, 11 October 2017, Aliaa-Athirah et al. FRI 90707 (holotype KEP, isotype SING) .

Description.

Rosette herbs. Leaves opposite; petiole pale green, to 7 cm long, not winged; lamina membranous to subcoriaceous, dark green above, sometimes with grey blotches, white-green beneath, narrowly oblong to elliptic, ca. 11 × 4–5 cm, base abruptly truncate, decurrent for 2 cm, margin entire, slightly wavy, apex unequal, slightly acute to blunt; midrib and veins slightly sunken above, glabrous beneath; lateral veins ca. 9–10 pairs. Inflorescences green, erect, terminal, racemose occasionally lower axils with pairs of flowers, dichasium with opposite branches, rachis up to 30 cm long or more, minutely hairy, branches ca. 14 cm long with up to 5 flowers; bracts green, ca. 1 mm long; pedicels very short, ca. 0.5 mm long; bracteoles minute, 0.5 mm long. Flowers suberect. Calyx divided near the base, lobes 5, equal, narrowly linear, 2–3 × 0.5–1 mm long, green, hairy outside, clasping the corolla tube. Corolla white outside, inside white with scattered minute purple spots except for the deep purple lower lip, deep purple at the median lobe, minutely glandular hairy outside, ca. 12–14 mm long, narrowly cylindric at base, tube 10 × 1 mm, expanding distally to funnel-shaped throat, upper lip erect, ca. 3 mm long, apex slightly bilobed, flat, lower lip unequal, the middle lobe much shorter. Stamens 2, filaments white, 6–7 mm long, inserted at the base of the throat, glabrous, anthers purple-white, inserted, positioned below the apex of upper lip, narrowly oblong, ca. 2 mm long, thecae 2, equal, both with minute mucronate appendages at base, densely covered with short stalked glandular hairs with dense white hairs along longitudinal line of dehiscence; staminodes absent. Nectary annular, cream-coloured, ca. 1 mm high, upper margin entire. Ovary green, cylindric, 1–1.5 mm long, densely covered in short glandular hairs, ovules many per locule; style white, up to 8 mm long, sparsely hairy, stigma hooked, less than 1 mm long, positioned between the anthers. Capsule narrowly cylindric, 10–12 × 1–2 mm, retinacula 6–7 per locule, calyx persisting after the fruit has fallen. Seeds up to 12 (probably more), obliquely ovoid, strongly compressed, ca. 1 mm longitudinal, surface minutely pitted, hairy.

Distribution and habitat.

Endemic to Kelantan, Peninsular Malaysia; known only from limestone hills. Species grows in small populations, always observed in shaded areas, rooting in cracks on thin soil on limestone rocks, almost to the summit of the hill.

Etymology.

The specific epithet refers to the limestone habitat of this species.

Provisional IUCN regional conservation status.

Endangered B 2 ab (i, ii, iii). Most Chiku limestone hills were visited, but only two to three hills were home to this new species. A part of Chiku limestone hills is scheduled for quarries. The survival of the species remains uncertain. The species also has been recorded in Perasu limestone hills, about 40 km away from Chiku hills. Parts of FELDA Perasu limestone have been quarried, and surrounding areas are currently disturbed by the road constructions. All hills lie outside the network of Protected Areas.

Additional specimens examined.

Peninsular Malaysia, Kelantan: FELDA Chiku , 11 October 2017, Aliaa-Athirah et al. 90712 ( KEP) , 10 October 2017, Wan Syafiq et al. FRI 90123 ( KEP) ; FELDA Perasu , 24 April 2019, Rafidah FRI 93064 ( KEP) .

Notes.

Ridley (1923) divided the Peninsular Malaysian species into two groups: (i) dwarf plants with single flower of long inflorescences and; (ii) shrubby plants with elongate stem. This new species falls into the first group (Table 1 ) together with Gymnostachyum decurrens Stapf var. decurrens and var. robinsonii (Ridl.) J. B. Imlay , G. diversifolium C. B. Clarke , G. pallens C. B. Clarke , G. kanthanense , and doubtful species recorded for Peninsular Malaysia, G. ceylanicum Arn. & Nees. The new species shows affinity with Gymnostachyum decurrens var. decurrens and var. robinsonii by its crowded rosette leaves at the base and its racemose and spicate inflorescences and G. pallens from its branched peduncle. It differs from the other species by not having a winged petiole and in having racemose inflorescences, occasionally lower axils with pairs of flowers and dichasium inflorescence with opposite branches.

Figures

Figure 1. Gymnostachyum calcicola Rafidah A habit B flower (side view) C flower (front view) D portion of inflorescence showing dichasial cymose branches E portion of infructescence.

Figure 2. Gymnostachyum calcicola Rafidah A flowering plant B portion of inflorescence with flowers C flower D flower with opened corolla E bract, calyx and carpel with corolla and stamens removed F indumentum of anther along longitudinal line of dehiscence G anthers (dorsal and ventral views) H seeds I fruit J-K attachment of seeds (all drawn by Mohd Aidil Nordin).

Figure 3. Home of Gymnostachyum calcicola.