Two new species of Codonoboea (Gesneriaceae) from Kenaboi State Park, Peninsular Malaysia

Abstract Two new Codonoboea species, C. kenaboiensis Syahida-Emiza, Y.Y.Sam & Siti-Munirah and C. ruthiae Syahida-Emiza, Y.Y. Sam & Siti-Munirah were discovered from the Kenaboi State Park, Peninsular Malaysia. Descriptions, illustrations, colour plates and provisional conservation status are provided.

forest was classified as water catchment, recreational, educational and wildlife forest in accordance with the National Forestry Act 1984.
In 2010, a scientific expedition to Gunung Besar Hantu was carried out to document the biodiversity at high elevation about 1,400 m. Seven years later in 2017, another expedition called the Lembah Jemaloi Scientific Expedition covered the remaining areas at lower elevations, especially the valley at Lembah Jemaloi. During the expeditions, two unknown species of Codonoboea were discovered in the lowland forest below 400 m elevation. After careful examination, the collections were shown to have a unique combination of characters that do not match any existing described species and hence, both are described here as new.
Codonoboea kenaboiensis Syahida-Emiza, Y.Y.Sam & Siti-Munirah is a small rheophyte discovered on the rocky riverbank of Sungai Kenaboi. This species is unique in its narrowly elliptic leaves with serrate margins. The plants are usually overshadowed by other larger species and are inconspicuous unless their purplish tubular flowers are blooming. On the other hand, Codonoboea ruthiae Syahida-Emiza, Y.Y.Sam & Siti-Munirah was found on the forest floor near one of the tributaries of Sungai Kenaboi. Its distant pairs of unequal leaves and attractive maroon flowers distinguish it from other ground flora.
Peninsular Malaysia is the centre of diversity for the genus Codonoboea, the most speciose genus in the Gesneriaceae family of Peninsular Malaysia, with at least 95 species recorded so far (Kiew andLim 2011, 2019;Lim and Kiew 2014). New taxa continue to be discovered and named as botanical collecting ventures into unexplored localities (Kiew and Lim 2019). Codonoboea is commonly found in primary forest from lowlands up to mountains growing on granite, sandstone and quartz-derived soils or rocks (Kiew and Lim 2011). Its distribution ranges from Peninsular Thailand, Sumatra, Singapore, Batam and Lingga Islands, Borneo, Palawan (the Philippines), Sulawesi and New Guinea (Lim and Kiew 2014). Description. Rheophyte, 10-20 cm tall. Stems woody, erect, wiry, unbranched. Leaves decussate, pairs spaced up to 0.5 cm apart, denser to the apex; petioles slender, 0.5-1 cm long, c. 0.1 cm diameter; laminas narrowly elliptic, 4.5-10 × 0.8-1 cm, coriaceous, mid-green above, pale green beneath, base attenuate, apex acute to attenuate, margin serrate; midrib and lateral veins sunken above, glabrous, prominent beneath, puberulous, lateral veins up to 30 pairs, generally opposite or alternately arranged, intercostal veins reticulate, slightly prominent. Inflorescences at upper leaf axils, erect, 1 per axil, cymes, 2-3-flowered; indumentum of floral parts a combination of glandular and simple hairs; peduncle 4-8 cm, purplish-maroon, densely hairy; bracts 3-3.5 × c. 1 mm, densely hairy, lanceolate, apex blunt. Flowers: pedicels 2-3 mm long, purplish, densely hairy; calyx mid-green, densely hairy, 5-lobed, narrowly lanceolate, lobes 1.2-1.5 × 0.2-0.8 mm, apex blunt; corolla tubular, 10-13 mm long, base 2 mm wide, dilating to 3 mm at the mouth, outside whitish to violet, sparsely hairy, inside whitish, glabrous, veins conspicuous; corolla lobes deeper violet, unequal in size, oblong, c. 3 × 2 mm, apex blunt; stamens 2, 3-3.5 mm long, filaments erect, c. 2.5 mm long, glabrous, anthers versatile, c. 0.8 mm long, c. 1 mm wide, white; nectary annular, c. 0.6 mm tall, rim toothed, glabrous; pistil yellowish-cream, c. 8 mm long, ovary c. 3.5 × 0.7 mm, sparsely hairy, style c. 4.5 mm long, white, sparsely hairy, stigma peltate, c. 0.7 mm across, papillose. Capsules cylindrical, 18-20 mm long, c. 1 mm wide at base, green, splitting adaxially when mature, calyx persistent. Seeds elliptic-oblong, c. 0.2 × 0.15 mm.   Ecology. Lowland dipterocarp forest, on rocks or steep earthy river banks, at 275-315 m altitude. Flowering from May to July. Codonoboea kenaboiensis grows on the lower levels of the riparian zone to about 1.5 m above the normal water level. Conditions are cool and damp with a thick layer of mosses covering the ground and shrubs and trees on higher ground leaning towards the river providing partial shade to the vegetation underneath. Such conditions are ideal for many plants but they are subjected to regular flooding events such as flash floods and annual floods during monsoon seasons. Only plants with rheophytic adaptations like C. kenaboiensis can survive the swift moving flood water. It has narrow leaves and roots that secure it firmly to the ground, preventing it from being uprooted by water currents. However, more frequent and intense flooding as a result of climate change might affect its long-term survival at Sungai Kenaboi.

Codonoboea kenaboiensis
Etymology. The epithet refers to the Kenaboi State Park, its only known locality. Conservation status. Vulnerable, VU D2. Codonoboea kenaboiensis is hyperendemic with a very small and restricted population at Sungai Kenaboi, Kenaboi State Park. Its small population and position in the flood zone is threatened by the increasing records of flood and extreme weather events caused by climate change. Tang (2019) has projected more rainfall events of high intensity and tropical storms in Malaysia as climate change intensifies. Under such circumstances, the seeds and seedlings of C. kenaboiensis will be washed away before they can firmly establish to the substrate thereby affecting its regeneration. Following the IUCN Standards and Petitions Committee (2019), C. kenaboiensis qualifies for VU D2 because the increased frequency of floods is expected to cause a population reduction and, due to its small population, the species could become Critically Endangered or Extinct in a very short period of time.
Discussion. Codonoboea kenaboiensis belongs to Codonoboea sect. Pectinati, characterised by narrow and serrate to deeply toothed leaves and small tubular flower (Ridley 1923;Lim and Kiew 2014). It closely resembles C. rheophytica, a recently described rheophyte from Terengganu (Kiew and Lim 2019). Both have distinctly narrow leaves (0.8-1 cm in C. kenaboiensis and 0.8-1.3 cm in C. rheophytica), serrate leaf margins and numerous lateral veins (30 pairs in C. kenaboiensis and 33-36 pairs in C. rheophytica). However, they are distinguished by the inflorescence and floral structures. Codonoboea kenaboiensis has simple cymes bearing 2-3 tubular flowers whereas C. rheophytica has solitary trumpet-shaped flowers. In addition, the violet flowers of C. kenaboiensis are much smaller (c. 1-1.3 cm vs 3-3.5 cm in C. rheophytica) than the white flowers of C. rheophytica.
Codonoboea species are common on stream and river banks but very few are true rheophytes. Other than C. rheophytica and C. kenaboiensis, C. densifolia (Ridl.) C.L.Lim and C. salicina (Ridl.) C.L.Lim are two other rheophytes found in Peninsular Malaysia (Kiew 1987). The narrow leaves of C. densifolia and C. salicina have entire to serrulate margins and fewer lateral veins (up to 20 pairs) that clearly distinguish them from C. kenaboiensis. In terms of inflorescence structure, both C. densifolia and C. salicina have cymose inflorescences similar to C. kenaboiensis but their campanulate flowers are distinct from the tubular flowers of C. kenaboiensis.
At Sungai Kenaboi, there is another Codonoboea species growing on the steep riverbanks. Codonoboea breviflora can easily be mistaken as a larger form of C. kenaboiensis that also has long narrow leaves and serrate leaf margin. However, the leaves of C. kenaboiensis are conspicuously smaller with shorter petioles (0.5-1 cm vs 1-2.5 cm long) and smaller laminas (4.5-10 × 0.8-1 cm vs 9-20 × 2.5-5.5 cm) compared to C. breviflora (Fig. 3). Upon closer examination, the leaf venation of C. kenaboiensis also proves to be distinct from C. breviflora. Codonoboea kenaboiensis has craspedodromus lateral veins (the veins run directly from midrib to the margin) whereas in C. breviflora the veins branch before reaching the margin. In addition, the single campanulate flower of C. breviflora instantly differentiates it from C. kenaboiensis.

Codonoboea ruthiae
Conservation status. Least Concern (LC). Codonoboea ruthiae is well protected within the Protected Area Network. Its existence in Kenaboi State Park and also at the water catchment forest in Sungai Lalang Forest Reserve, Selangor, which is categorised as a Protection Forest, is legally secured under the National Forestry Act 1984 (Ministry of Water, Land and Natural Resources 2019). Furthermore, no threat to the species population has been identified.
Discussion. Codonoboea ruthiae belongs to Codonoboea sect. Didymanthus (Lim and Kiew 2014) characterised by opposite and well-spaced petiolate leaves. It closely resembles C. ramosa in its slender-branched stem, distant pairs of leaves, one of each pair much smaller, oblique lamina base and trumpet-shaped flowers (Ridley 1923). However, C. ruthiae can be distinguished from C. ramosa by a combination of characters shown in Table 1.