﻿ Coleus (Lamiaceae) in Peninsular Malaysia including two new species

﻿Abstract In Peninsular Malaysia, Coleus is represented by five species. Two, C.hairulii Kiew and C.rafidahiae Kiew, are new species. Both are narrowly endemic and restricted to limestone hills as is C.kunstleri (Prain) A.J.Paton. All three are Critically Endangered. Coleusscutellarioides (L.) Benth., although widespread, is probably not indigenous. It is also a common ornamental, while C.monostachyus (P.Beauv.) A.J.Paton is a recent introduction that has spread rapidly and threatens to become a troublesome weed.


Introduction
The flora of Peninsular Malaysia now includes five species of Coleus, compared with the two previously recorded under Plectranthus by Keng (1978) and Bramley (2019). Coleus has recently been recognised as distinct from Plectranthus (Paton et al. 2019). Coleus scutellarioides (L.) Benth. is a widespread lowland species, often associated with villages, and C. kunstleri (Prain) A.J. Paton is very rare and known from just two limestone localities. Recent exploration of limestone karsts in Peninsular Malaysia has led to the discovery of the two new species that are described here. Coleus monostachyus (P.Beauv.) A.J. Paton is an African weed recently introduced and now, after a decade, has rapidly become widespread and is found everywhere in ruderal habitats (Kiew 2016). The three limestone species are endemic and restricted to karst limestone (Map 1). are each known from a single locality, while C. kunstleri, although known from two localities (Kuala Dipang, Perak and Pulau Langgun, Langkawai, Kedah) is unlikely to still grow in Kuala Dipang because it has been, and is, heavily disturbed by mining and, although the area has been regularly visited for botanical collecting, this species has not been recollected for more than 130 years. Today, it is therefore extant at a single locality. In contrast, C. scutellarioides does not grow on limestone and is widespread, though not common, on the fringes of lowland forest. It is not endemic. For endemic species, the conservation status is the global conservation status, while for C. scutellarioides, it is the regional conservation status that applies only to the Peninsular Malaysian population (Chua and Saw 2006).
Botanical exploration has shown that many species (about 15%) of the limestone flora have extremely local distributions (Kiew et al. 2017). One hundred taxa (species, subspecies or varieties) are known from a single karst hill, while a further 92 are known from two to four karst hills or islands. These species are particularly endangered by extinction. The three Coleus species that are endemic and restricted to limestone are further examples of this phenomenon.

Taxa cultivated in Peninsular Malaysia
Coleus, Coleus scutellarioides, is widely available in nurseries and popular as an ornamental plant for its incredible variety of leaf colour (reds, purples and yellows) and patterns of variegation. In Peninsular Malaysia, it seldom flowers. Its local Malay name is pokok ati-ati. Several minor medicinal uses have been ascribed to it (see below under species).
Indian borage, Coleus amboinicus Lour., said to be native to India, is commonly grown in pots in home gardens for its medicinal value (for a dry cough a decoction of the leaves is drunk to sooth the throat). It rarely flowers and does not fruit. It is readily distinguished from the other species by its thick, hairy, succulent, harshly aromatic leaves. Its local Malay name is daun bangun-bangun.
Plectranthus 'Mona Lavender' is currently a very popular floriferous species with deep purple flowers that grows well in the highlands at Cameron Highlands, Pahang, and has caused confusion with the public because it is marketed as a true lavender (Kiew 2016). It is a hybrid developed in the 1990s in the Kirstenbosch Botanic Gardens, Cape Town, South Africa.
The edible C. rotundifolius (Poir.) A.Cheval & Perrot, although once reported from Peninsular Malaysia (Burkill 1966), is today not planted even as a curiosity (Kiew 2016). Suddee et al. (2004) Suddee et al. 2004) from southern Thailand in its habit (both are low, little branched or unbranched herbs), in their inflorescences with conspicuous side branches and cymules with more than 3 flowers, but Coleus hairulii ( Figure 2) is different (Table 1) in its short branches from the inflorescence axis 2.5-4 cm long, i.e. 3-5 times shorter than the inflorescence length (vs. branches from the inflorescence axis 5.5-10 cm long and 2-3 times shorter than the inflorescence), and its calyx 6-7 mm long in fruit (vs. 4-6 mm long).
Provisional conservation status. Critically Endangered B1ab(i,iii,iv). The species is known only from one locality, with a low population size, estimated at less than a Ecology. Restricted to a limestone karst hill at ca. 90-155 m on lower slopes of the hill, growing in soil-filled cracks in the limestone rocks on or near wet, shaded vertical cliffs or between deep pinnacles on a low summit, locally common in a restricted area. It is not known if it is short-lived or an annual plant.
Etymology Note. In discussions with AJ Paton (pers. comm.), he pointed out that the type of Plectranthus glabratus (Benth.) Alston (now C. paniculatus) from Chennai (Madras) is a more robust plant with a thicker stem, bigger leaves and relatively shorter branches of the inflorescence compared with the three specimens from southern Thailand. Coleus hairulii resembles specimens from southern Thailand that are also all from limestone rocks (Suddee et al. 2004).  Note. The description is based on specimens from Peninsular Malaysia. Description. Erect herb, almost shrubby, not aromatic, without tubers. Stem quadrangular, densely hairy on the angles, hairs descending ca. 0. 5 mm long, green, woody but brittle, to 30 cm tall, ca. 4 mm diameter, at first unbranched, flowering at ca. 20 cm tall, soon branching near the base, internodes (2.5-)4.5-6.5 cm, branches ascending, to 29 cm long. Leaves held horizontally; petiole 2-5.6 cm long, narrowly winged in the upper third, grooved above, densely hairy on the angles; lamina broadly ovate, (3.5-)6-13.5 × (2.5-)4.5-11.5 cm, base rounded or slightly truncate, shortly decurrent into the petiole, margin shallowly crenate, apex acute, tip rounded, membranous, glabrous and completely dull green above, pale beneath, lateral veins ca. 4 on either side of the midrib, impressed above, beneath prominent and finely short hairy. Inflorescence terminal on stem and branches, spicate, ca. 14 cm long in unbranched plants, in branched plants 21-38 cm, often with a subsidiary pairs at the base ca. 16.5-23 cm long, peduncle short 3-5 cm, 8-8.5 cm in inflorescences from the lower branches; peduncle and rachis quadrangular, finely pubescent on the angles; verticils 1-2 cm apart at the base, ca. 0.5 cm apart near the apex, each verticil with two sessile, condensed cymes each with 3-5 flowers. Bracts broadly ovate apex caudate, keeled, ca. 4 × 2.5 mm, pale green, deflexed and appressed to rachis. Pedicels reddish on the upper side, slightly excentrically attached behind the posterior lip, minutely pubescent, 1.5-2 mm long. Flower with calyx funnel-shaped, pale green, densely pubescence 2-3.5 mm long, in fruit 5-5.5 mm long, upper lip curved upwards, oval, minutely punctate at the apex, ca. 4-4.5 mm long, lower lip broadly oval with two fine apical teeth, curved upwards and closing the throat; corolla 8.5-10 mm long, minutely pubescent outside, tube abruptly decurved above the calyx, dilating to the mouth, white except for the upper lip and lateral lobes outlined in deep purple and the deep purple lower lip 3-4 mm long; stamens fused at base, filament white, glabrous, anthers, ca. 0.25-0.3 mm long, deep purple; stigma ca. 0.4 mm long, positioned above the anthers. Nutlets 4, plain brown, broadly ovoid, almost 1 mm long, producing mucilage when wet.

Coleus kunstleri (Prain) A.J. Paton in Paton et al., Phytokeys 129 (2019) 63.
Distribution. Native in tropical West Africa, this is a recent introduction into Peninsular Malaysia and Singapore, probably an escape from the horticultural trade (Kiew 2016). First collected in Peninsular Malaysia in 2003, it is now naturalised and since about 2010 has rapidly become widespread. Apparently, it has not yet been recorded from Southeast Asia (Suddee et al. 2004).
Ecology. In Peninsular Malaysia, it is found in light shade to fully exposed conditions in almost all lowland habitats associated with disturbance, e.g. roadsides, plantations, farms and gardens. It begins to flower at 20 cm tall, and its many-flowered spikes produce fruits that shatter at the slightest touch, scattering hundreds of seeds. This makes it a weed that is extremely difficult to eradicate. The seeds are sticky and may be dispersed by animals or water but long distance dispersal is probably effected by soil on vehicles or in planting material. It therefore threatens to become a noxious weed in nurseries and gardens where it cannot be exterminated by herbicides.
Distribution. Endemic in Peninsular Malaysia, Kelantan: Kuala Betis, Gunung Biol. Known only from two specimens from the type locality (Map 1).
Provisional conservation status. Critically Endangered B1ab(i,iii,iv). The species occurs on a single karst limestone hill that lies outside the network of Totally Protected Areas. It is known from a single small population. (Assessed by A.R. Rafidah).
Note. Ridley (1923) and Burkill (1966) considered the coleus of gardens (i.e. Coleus blumei) was introduced from Java and was distinct from Malayan C. atropurpurea. These two species are recognized as conspecific and are currently known as Coleus scutellarioides (Paton et al. (2019) with the result that the description has expanded to include the huge range in leaf size, shape and colour of the ornamental forms that are not seen in the wild form of Malaysian population. The description above is based on the wild form that has smaller, plain green leaves. Unlike Scutellaria discolor Wall. ex Benth., it is not found deep in forest and is seldom found in flower. That it is usually associated with forest edge, often close to habitation, suggests that many of these populations have been established for their medicinal properties.
On account of it being extremely variable, Keng (1978) and Bramley (2019)  Ecology. In Peninsular Malaysia, from forest edge and often near villages throughout the lowlands to 350 m elevation (Kiew 2014), sometimes in forest by streams but not from limestone hills as reported by Keng (1978). That the forest localities are often close to villages and it has medicinal uses suggests these populations may have been planted, particularly because this species seldom flowers but can easily be propagated by stem cuttings. Etymology.
Greek -oides = resembling; Scutellaria L., a genus in Lamiaceae. Uses. In Peninsular Malaysia, it has always been commonly known as 'coleus' and in Malay as pokok ati-ati. Cultivated forms are popular ornamental plants and come in a great variety of multicoloured, variegated foliage. In Cameron Highlands, they are grown in great quantities for home gardens. The colour of plants grown in the highlands, ca. 2000 m, is more vivid than those grown in the lowlands.
It is a minor medicinal plant used to cure a wide range of ailments. Burkill (1966, pg. 643) reported it was a remedy for heart disease, heart burn, inflammation of heart; sensitive skin, stimulates digestion and for congestion of the liver that causes swellings of the hands and feet, amongst other ailments. Among the aboriginal population, the Besis people (now more commonly known as the Mah Meri) call it torek, and plant it around their graves. They also traditionally use it as the brush used for sprinkling holy rice-gruel over a new clearing (Burkill 1966).
Peninsular Malaysia specimens examined (* indicates specimens collected in villages that are presumed to be cultivated): Johor: Pulau Aor Fielding s.n. 1892. MelaKa: