Indonesia • Sumatra: Aceh Province, c. 900 m, RIO 9118 (holotype, BO!) (detailed localities are not shown here for conservation purpose).

Chiloschista tjiasmantoi is morphologically similar to C. javanica, but differs in having oblong-obovate petals (vs. broadly elliptic to ovate petals), narrowly oblique oblong side lobes with truncate to obtuse apex (vs. relatively straight triangular side lobes with obtuse apex), a lip sac that has a “V” shape in longitudinal section view with a narrow angle of about 45–50° (vs. a lip sac that has an “L” shape in longitudinal section view with a wide angle of about 90°), and a very narrow cavity between the apex of the hairy callus and the thick curved front lobe of the lip (vs. a rather broad cavity).

Epiphytic herb. Roots numerous, spreading, terete to slightly flattened, 2.0–3.5 mm in diameter, greyish-green when wet and becoming grayish-white when dry, grow radially from a short stem as the central, and mature individuals can grow elongated to reach more than 30.0 cm. Stem reduced, very short, erect, simple 2.0–4.0 mm long, up to 3.0 mm in diameter, densely covered with dry stem bracts. Stem bracts are triangular active, and persistent, and encircle the stem tightly. Leaves one or two, 4–7 mm long, deciduous, unseen in cultivation. Inflorescence axillary, arising among the roots gap, pendulous, up to 31.0 cm long in total, peduncle c. 2.0 mm in diam. near base, terete, densely covered with short white hairs, purplish near base and becoming purplish green toward apex, sometimes branched at the base, up to 30 flowered per rachis, flowers arranged spirally in a slightly zig-zag pattern and open simultaneously, each flower can last up to 5 days; flower bracts triangular, 2.0–3.0 mm long × 1.5–2.0 mm wide, acuminate to caudate, pubescent, greenish and soon becoming brown when old. Pedicel and ovary about 2.0 mm long, terete, brownish-green to purplish-green, covered with whitish hairs. Flower rather thin-textured, 1.0–1.2 cm high × 1.0–1.2 cm wide, open widely, sepals and petals yellowish cream or yellow with orange or reddish spots, labellum yellowish cream with reddish or orange spots on their sac, column yellowish green with orange tinge on its foot. Dorsal sepal oblong-elliptic, 5.0–6.0 mm long × 4.0 mm wide, obtuse to rounded, both surfaces pubescent. Petals oblong-obovate, 5.0–6.0 mm long × 3.0–4.0 mm wide, truncate to rounded, both surfaces pubescent. Lateral sepals obliquely oblong-elliptic, 6.0 mm long × 4.0–5.0 mm wide, obtuse, both surfaces pubescent. Lip immobile, minutely papillose externally, 3-lobed, deeply saccate, indistinctly canaliculated ventrally, 2.8–3.2 mm long, 4.0–4.5 mm high (from side lobes apex to basal part of sac), 2.0–2.5 mm wide at front; side lobes erect to slightly curved inwards, obliquely oblong to rather falcate, c. 2.0 mm long × c. 1.5 mm wide near base and narrowed gradually to about 1.0 mm near apex, apex truncate to rounded, yellowish cream with red streaks on internal surface; front lobe subtrapezoid, short c. 1.0–1.5 mm × 1.5 mm, apex truncate to slightly emarginate, curved; sac ovate to subrectangular from front view, “V” shape in longitudinal section view, 2.0–2.5 mm long × 2.0–2.3 mm wide, apex truncate or retuse or slightly bilobed, yellowish cream with pale reddish or pale orange spots on external surface around the apex; callus a fleshy thickening arise from basal to middle of the internal front wall, split into two oblong hairy callus that rises up to sac opening, creating a small narrow cavity between apex of the hairy callus and the thick curved front lobe of the lip; column short 1.5–2.0 mm long (excluding the anther cap), foot about 2.2–2.5 mm long; anther cap cucullate, yellowish or cream, c. 1.5 mm × 1.5 mm; pollinarium two unequal globose on a narrowly linear to triangular stipe, yellow. Fruit not seen.

Based on the existing data, the distribution of Chiloschista tjiasmantoi may be restricted to Aceh Province, the most northern part of Sumatra Island. This new species is currently only known from five locations in two different regencies at elevation ranging from 700–1000 m. The populations of this species were mostly found growing epiphytically on old coffee trees (Coffea spp.) and shade trees (Leucaena spp.) in the local coffee plantations, together with Vanda pumila (Orchidaceae), in a windy and semi–opened wet habitat with medium sunlight intensity. Flowering recorded in mid-July, early November to late December.

The specific epithet “tjiasmantoi” honors Wewin Tjiasmanto, the chairman of Tjiasmanto Conservation Fund and a philanthropist concerned with the Indonesian plant conservation.

Chiloschista tjiasmantoi seems rather difficult to cultivate at lower elevations (300 m. a.s.l). However, it was successfully grown by attaching it to a slab of tree fern with a top dressing of moss to prevent the roots from drying out, under a light intensity of about 30–75% with good air circulation and humidity levels of about 80% or more.

This new species is morphologically similar to C. javanica (Fig. 1C, D, 4C, F) and C. sweelimii (Fig. 4A, D). However, there is a geographical separation among these three species. C. tjiasmantoi is thus far only recorded from Aceh Province, the northernmost region of Sumatra Island; C. sweelimii occurs in the Malay Peninsula and Vietnam, and C. javanica is endemic to Java Island.

Figure 1. 

Chiloschista tjiasmantoi sp. nov. (A, B) and Chiloschista javanica (C, D) A inflorescence B flower, oblique view. C flower, front view D flower, oblique view. Photos by Destario Metusala.

Chiloschista tjiasmantoi differs from C. javanica in having narrower oblong-obovate petals, narrowly oblique oblong side lobes with truncate to obtuse apex, a lip sac that has a “V” shape in longitudinal section view with a narrow angle of about 45–50°, a narrow cavity between the apex of the hairy callus and the thick curved front lobe of the lip. Meanwhile, C. javanica has broadly elliptic to ovate petals, relatively straight triangular side lobes with obtuse apex, a lip sac that has an “L” shape in longitudinal section view with a wide angle of about 90°, and a rather broad cavity between the apex of the hairy callus and the thick curved front lobe of the lip.

Figure 2. 

Chiloschista tjiasmantoi sp. nov. A habitus with inflorescence B flower, natural shape, front view C flower, natural shape, oblique view D dorsal sepal, flat shape E petal, flat shape F lateral sepal, flat shape G column and foot, oblique view H column and foot, front view I column and lip, side view J pollinia K stipe and viscidium L lip, above view M lip interior, back view. Line drawing by Destario Metusala from RIO 9118.

Furthermore, C. tjiasmantoi differs from C. sweelimii in having sepals and petals with hairs on both sides, oblong-obovate petals, a broadly oblong-elliptic dorsal sepal, basal front lobe without any callus, an ovoid to subrectangular lip’s sac from front view with a truncate to slightly bilobed apex, and an oblong fleshy thickening that arises from basal to middle of the internal front wall. This thickening then divides into a 2-lobed hairy callus that rises near the sac opening, creating a cavity between the apex of the hairy callus and the thick curved front lobe. In contrast, C. sweelimii has sepals and petals with hairs only on their adaxial surface, ovate to orbicular petals, an ovate dorsal sepal, basal front lobe with large callus on either side (each c. 1.5 × 1.0 mm), a triangular shaped lip’s sac from front view with pointed obtuse apex, and the absence of prominent internal callus inside the lip’s sac (Teck 2016). A comparison between the new species and its morphological allies is shown in Table 1.

Figure 3. 

Chiloschista tjiasmantoi sp. nov. Flowering plants in situ. Photos by Alfajaruddin.

This new species will be the fifth Chiloschista species in Indonesia, and the first record of this genus on Sumatra Island. With the exception of C. phyllorhiza, the species are endemic to the country and appear to have restricted distributions. Although the flowers of some species appear nearly identical in appearance, the internal structure of the lip can be very different, which suggests this would be a good key character for further identification of this genus (Gyeltshen et al. 2019; Dalstrom and Kolanowska 2020). A deeper investigation into its floral morphological variation needs to be carried out in the future, as this is essential to support species delimitation of Indonesian Chiloschista (Metusala 2020b; Metusala et al. 2020).

Figure 4. 

Lip of three Chiloschista species A C. sweelimii, natural shape, front view B C. tjiasmantoi, natural shape, front view C C. javanica, natural shape, front view D C. sweelimii, longitudinal section, flat shape, side view E C. tjiasmantoi, longitudinal section, flat shape, side view F C. javanica, longitudinal section, flat shape, side view. A and D redrawn after Ong Poh Teck in Teck (2016). Drawn by Destario Metusala.

Chiloschista tjiasmantoi was recorded from five locations in Aceh Province. Based on currently available data, the Extent of Occurrence (EOO) of this species is 117.01 km² with user-defined cell width = 2 km (criterion B1: < 5,000 km²) and Area of Occupancy (AOO) value of 20.00 km² (criterion B2: < 500 km²). Their natural habitat is threatened by land conversion, especially from large-scale coffee plantations. Existing populations were estimated to be less than 2,500 mature individuals (≤ 250 in most subpopulations) where they mostly found attached to the branches of coffee trees and its shade trees (Leucaena spp.). Unfortunately, coffee plantations provide a vulnerable habitat for this new orchid species as they can be pruned or cut down at any time. Moreover, many coffee farmers believe that this orchid is a harmful parasitic plant and eradicate them by clearing the coffee branches from any epiphytic plants. This species has also been found traded on domestic online platforms as an ornamental orchid, although currently in small quantities as its habit and small flowers are considered less attractive to Indonesian hobbyists. In many cases, unsustainable commercial harvesting may have a significant impact on the viability of wild orchid populations (Hinsley et al. 2018). Therefore, I consider this species to likely be in the Endangered category B1 and B2+ab (i,ii,iii,iv), C2+a (i) (IUCN Red List Categories and Criteria).

It has been well-documented that ecosystems in the highland of Aceh Province are severely affected by climate change, particularly through increased temperatures (Schroth et al. 2015). This could also have a major impact on various sensitive plant species, such as many highland epiphytic orchids, including natural populations of Chiloschista tjiasmantoi. Therefore, conservation-based researches are needed to determine the vulnerability of these species to climate change-related pressures, especially drought stress (Al Farishy et al. 2017; Arimy et al. 2017; Metusala 2017b; Metusala et al. 2017; Suffan et al. 2021; Ishmah et al. 2021; Trimanto et al. 2023).