Chroesthes faizaltahiriana Siti-Munirah, 2021

Yunoh, Siti-Munirah Mat, 2021, Chroesthes (Acanthaceae) in Peninsular Malaysia, including a new species from Kelantan and a new record from Terengganu, PhytoKeys 174, pp. 127-146 : 127

Chroesthes faizaltahiriana Siti-Munirah sp. nov. Figs 1 , 2 , 3

Diagnosis.

Chroesthes faizaltahiriana most closely resembles C. longifolia ; however, it differs in its inflorescence type, the presence of a terminal raceme not branching (vs. terminal raceme branching) and posterior lobe size ratio 1:4 (vs. 1:2) and corolla length 4.5-5.5 cm (vs. 2-3 cm) and in the corolla tube and lobes being entirely bright yellow to dark orange (vs. entirely dark purple, purplish-red or occasionally white externally) and other significant characters (see Table 1 ).

Type.

Malaysia. Peninsular Malaysia: Kelantan, Gua Musang Distr. , Berangkat FR , ca. 822 m alt., 26 Feb 2020, Siti-Munirah, FRI 91215 (holotype KEP!, barcode KEP 280001 ) .

Description.

Shrubs 0.7-1 m high. Stems terete, erect, not branched, surface glabrous, diameter ca. 2 mm, swollen at nodes. Leaves opposite; petiole 0.2-1 cm long; straight or twisted (makes the leaf arrangement look decussate); leaf blades elliptic, lanceolate to oblanceolate, 4.5-19 × 1.5-5.5 cm, both surfaces glabrous, lateral veins ca. 8-10 on each side of mid-vein, base attenuate to cuneate, margin entire, apex acute to acuminate. Inflorescence a terminal raceme (unbranched), up to 13 cm long; flowers secund (one bract at each node being sterile, the other bracts subtending each flower), ca. 10-flowered; glandular-pubescent on most parts; peduncles ca. 1 cm; bracts narrowly lanceolate, 20-30 × 2-5 mm, apex acute, glandular-pubescent, conspicuously 1-nerved; bracteoles narrowly lanceolate, 10-15 × 1-2 mm; pedicel short, ca. 1-2 mm long. Calyx 2-3 cm long, posterior lobe lanceolate, 30 × 7 mm, 3-5-nerved, apex acuminate; two anterior lobes, elliptic-lanceolate, 22 × 2-2.5 mm, 1-nerved, apex acuminate; two lateral lobes, linear-lanceolate, 20 × 1 mm, 1-nerved; all glandular-pubescent on both sides; all greenish. Corolla bilabiate, orange-yellow, ca. 4.5-5.5 cm long; outer surface pale yellow, glandular-pubescent; inner surface bright orange-yellow to orange with dark orange spots (or stripes), glabrous; tube with cylindrical basal portion ca. 2 cm long, expanded throat ca. 1.5 cm long; upper lip shortly two-lobed (8-9 mm long), lower lip deeply three-lobed (8-10 mm long). Stamens 4, didynamous, included in the throat, inserted at the base of the inflated part of the corolla, longer pair with filaments ca. 1.5 cm long, shorter pair with filaments ca. 1.2 cm long, all filaments with sparse glandular trichomes on the surface; anther thecae ca. 1-2 mm long, basal spur pointed, surface cover with simple trichomes. Pistil whitish-green; ovary ovoid, 1.5-2 mm long, apex pubescent; style ca. 3.2 cm long, pilose below, glabrous above; stigma subcapitate, minutely bilobed. Fruit not known.

Distribution.

Endemic to Peninsular Malaysia, Kelantan. Currently known only from the type collection from Berangkat FR, 5°07'55.5"N, 101°55'28.5"E (Map 1 ) .

Ecology.

Chroesthes faizaltahiriana is found in upper hill dipterocarp forests under shade at 822 m elevation. It was found flowering in February in patches of unlogged forest beside a logging road (Fig. 4 ).

Etymology.

Chroesthes faizaltahiriana is dedicated to Mohd Faizal Mat Tahir (known as Faizal Tahir), the husband of Siti-Munirah for his strong support in many ways towards the author’s botanical work.

Conservation status.

Critically Endangered B 2 ab(ii,iii). Following the IUCN Red List Categories and Criteria ( IUCN 2019), this species is assessed as critically endangered because it is only known from one locality and AOO is less than 10 km 2. Furthermore, about eight individuals were observed (all at the flowering stage). The collection locality is within the forest reserve, in an area of disturbed forest near a logging road at an elevation of 822 m. The status of the population is uncertain because the active selective logging activity within the forest reserve is ongoing. It is certainly not within a Totally Protected Area. During the 3-day visit to Berangkat FR, no other populations of C. faizaltahiriana were found. A further survey is needed to obtain more information that could estimate and determine the population size of this species.

Notes.

Based on the general morphology of this plant, C. faizaltahiriana is close to C. longifolia , which was previously the only known species of Chroesthes in Peninsular Malaysia. However, a detailed comparison has shown that its inflorescence type is entirely different (Fig. 5 , Table 1 ). Additionally, its phytogeography is also different when compared to C. faizaltahiriana , which is endemic to Gunung Berangkat (Kelantan) in upper hill dipterocarp forest (822 m a.s.l.), while C. longifolia is a widely distributed species inhabiting lowland dipterocarp forest. Based on herbarium specimen collections of C. longifolia at Kepong Herbarium ( KEP) and the Singapore Herbarium ( SING), it has been recorded in Kedah, Perak, Kelantan, Terengganu, Pahang, Selangor, Negeri Sembilan, Melaka and Johor. C. faizaltahiriana is a distinctive species amongst Chroesthes due to its flower colour. It is the only Chroesthes species with bright orange flowers internally. The flowers of C. longifolia are entirely dark purple to deep purplish-red (occasionally white externally), while the flowers of C. lanceolata are white, spotted pink to purple and those of C. bracteata are reported as pale pink, spotted with red.

Figures

Figure 1. Chroesthes faizaltahiriana Siti-Munirah A habit of the whole plant B inflorescence (front view) C inflorescence (side view) D flower with bracteoles and calyx E perianth lobes (flower from front view) showing the anthers F calyx and bracteoles G bract H bracteoles I calyx (a) anterior, (l) lateral, (p) posterior lobes (photo of a dry specimen) J corolla (inner view) K corolla (outer view) L stamens. (All photos by Siti-Munirah MY).

Map 1. Distribution of Chroesthes faizaltahiriana (▲) and C. lanceolata (■) in Peninsular Malaysia.

Figure 2. Chroesthes faizaltahiriana Siti-Munirah with scale A inflorescence B one floral unit with calyx and bracteole C corolla lobes (All photos by Siti-Munirah MY).

Figure 3. Chroesthes faizaltahiriana Siti-Munirah A habit B a flower with bracteoles and calyx front side view C perianth lobes (flower from front view) D bract E bracteole F calyx G corolla (inner view) showing the stamens and pistil H pistil I cross-section of the ovary J stigma K 1 anthers front view K 2 anthers side view. All from FRI 91215, drawn by Mohamad Aidil Noordin).

Figure 4. Habitat of Chroesthes faizaltahiriana Siti-Munirah A plant in its original habitat B new logging road beside the population C plant found on the bank of an old logging road (white arrow). (All photos by Siti-Munirah MY).

Figure 5. Inflorescence of Chroesthes longifolia from four localities A, A 1 Pasoh FR (Negeri Sembilan) B, B 1 Tembat FR (Terengganu) C, C 1 Nerus FR (Terengganu) D, D 1 Gn. Aais FR (Pahang). (Photos: A, A 1 Yao TL B, B 1 Siti-Munirah MY C, C 1 Imin K D, D 1 Sam YY).