Research Article
Research Article
Gymnostachyum calcicola (Acanthaceae), a new species from limestone karst of Peninsular Malaysia
expand article infoAbdul Rahman Rafidah, Abdul Rahman Ummul Nazrah, Poh Teck Ong
‡ Forest Research Institute Malaysia, Selangor, Malaysia
Open Access


A new species, Gymnostachyum calcicola Rafidah, sp. nov. (Acanthaceae) is described from limestone karst in Peninsular Malaysia. Characters distinguishing it from related species, colour photographs, botanical illustration and provisional conservation status are provided.

Key words

Andrographideae, endemic, flora, Kelantan, taxonomy


Gymnostachyum Nees (Acanthaceae) is a genus consisting of about 30–50 species distributed mainly in tropical Asia (Hu et al. 2011; Deng 2014; Mabberley 2017; Deng et al. 2020; Manzitto-Tripp et al. 2022). The genus is characterized by a combination of two stamens and many seeds (Hansen 1985), absence of staminodes, ovary with 3-several ovules per locule, capsule cylindrical, and seeds compressed, covered with hygroscopic hairs (Lindau 1895). It belongs to tribe Andrographideae (Lindau 1895; Scotland 1992; Scotland and Vollesen 2000; McDade et al. 2008), however Somprasong et al. (2015) placed Gymnostachyum under subtribe Andrographinae. In Peninsular Malaysia, Clarke (1908) recognized eleven species of Gymnostachyum, including ten new species, while Ridley (1923) recorded Gymnostachyum with 13 species (including four doubtful species) and described a new species Gymnostachyum hirtum Ridl. from Perak (Ridley 1926). Tan et al. (2014) described Gymnostachyum kanthanense Kiew from a limestone hill, Gunung Kanthan, Perak.

The discovery of this distinctive new species is part of the comprehensive survey of the Peninsular Malaysia limestone flora in 2017. The species was found on the limestone hills in Federal Land and Development Authority (FELDA) Chiku and Perasu in Kelantan, and is endemic in Kelantan. The species inhabits partially shaded areas, and roots in cracks with thin soil layer on rocks at the base to the summit of karst limestone. After carefully examining the herbarium specimens and living material and reviewing the relevant literature, here we concluded that the newly discovered plants represented an undescribed species. Herewith, the new species is described and illustrated in detail.

Materials and methods

Measurements and morphological character assessments of the new species were undertaken and described using specimens collected from their natural habitat and living materials grown in the Forest Research Institute Malaysia (FRIM) Biodiversity Nursery. Photographs of the habit and all parts of the plants were made and botanical line drawings of floral and fruiting parts were prepared. Materials collected were deposited at the herbarium of Forest Research Institute Malaysia (KEP) and the flowers were preserved into the spirit collection in Copenhagen mixture. The available Gymnostachyum specimens from other herbaria such as BK, BKF, CAL, KLU, SING, UKMB and PSU were examined (herbarium acronyms follow Thiers 2024, continuously updated). In addition, images of the type specimens of Gymnostachyum were obtained from JSTOR Global Plants ( and Tropicos ( The provisional conservation assessment is based on the IUCN Red List Categories and Criteria Version 3.1 (IUCN 2012) and guidelines of the IUCN (2022).

Taxonomic treatment

Gymnostachyum calcicola Rafidah, sp. nov.

Figs 1, 2, 3


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.


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

Map 1. 

Map of the Peninsular Malaysia indicating the location of Gymnostachyum calcicola in Peninsular Malaysia.


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.

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.

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.

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).


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

Provisional IUCN regional conservation status

Endangered B2 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.

Figure 3. 

Home of Gymnostachyum calcicola.

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).


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.

Table 1.

Comparison of Peninsular Malaysia species in Gymnostachyum in Group 1.

Characters / Species G. calcicola G. decurrens var. decurrens G. decurrens var. robinsonii G. diversifolium G. ceylanicum* G. kanthanense G. pallens
Petiole not winged broadly-winged winged winged winged not winged winged
Base abruptly truncate broad abruptly truncate broad unknown abruptly rounded or truncate abruptly truncate
decurrent for 2 cm undulate margin, decurrent decurrent decurrent undulate margin, decurrent decurrent for 2–8 mm shortly decurrent
Indumentum surface (both) Glabrous pubescent scabrid pubescent pubescent pubescent densely punctate
Type racemose spikes racemes spikes spikes spikes spike
dichasium inflorescence with opposite branches several branched 1 to 3 several 3 slightly branched
Flower occasionally lower axils with pairs of flowers single single single single opposite or in long spikes in short cymes on one side of the rachis single
Colour green purple green pale green dark green purplish green green
colour white white unknown pale blue pinkish / pale purple white tinged purple white
length (mm) 12–14 12–15 10 25 12 18 12
lower lip (median) deep purple violet unknown purplish (all) yellow deep purple white
indumentum minutely glandular hairy glandular pubescent glandular pubescent glandular and e-glandular hairs unknown stalked glandular hairs unknown
length (mm) 10–12 18 12 unknown unknown 12 > 12


We would like to thank the staff of the Flora Biodiversity Programme, FRIM who helped in botanical collections, to all the Merapoh and FELDA Chiku guides for assistance in the field, to Mohamad Aidil Noordin and Wendy Yong for preparing the botanical drawing and distribution map, and also to Dr Ruth for her fruitful comments in this manuscript. Special thanks to our former and current FRIM Director General and former Forest Biodiversity Director, Dr Richard Chung for his strong support of this project. We also thank Kelantan Forestry Department for permission to make botanical collections in Kelantan State. We thank the curators of the following herbaria for access to examine herbarium specimens and providing the specimens on loan: BK, BKF, CAL, KEP, KLU, SING, UKMB and PSU.

Additional information

Conflict of interest

The authors have declared that no competing interests exist.

Ethical statement

No ethical statement was reported.


This research is financially supported by National Conservation Trust Fund (NCTF) Grant, under the Project “Towards conservation strategy/policy for limestone hills in Peninsular Malaysia: Understanding and documenting plant biodiversity with focus on Kelantan and Perlis limestone hills (Phase 2)” and under the Twelfth Malaysia Plan 2021-2025.

Author contributions

All authors have contributed equally.

Author ORCIDs

Abdul Rahman Rafidah

Abdul Rahman Ummul Nazrah

Data availability

All of the data that support the findings of this study are available in the main text.


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