Ardisia silamensis Utteridge, Julius & Suzana

Utteridge, T.M.A., Julius, A. & Sabran, S. 2014. Ardisia silamensis, a new ultramafic species from Borneo; studies in Malaysian Myrsinaceae II. Kew Bulletin 69: 9510. DOI https://doi.org/10.1007/s12225-014-9510-4

Type

Type: Malaysia, Sabah, Lahad Datu, Mt Silam, 2800 ft [c. 853 m], 9 March 1972, fl., Shea SAN 75169 (holotype SAN!; isotypes K!, L, SING).

Morphology General Habit

A small tree 1 – 10 m high, branches glabrous or scaly hairy with very short rusty hairs giving a scaly appearance, soon glabrescent

Morphology Leaves

Leaves alternate; petiole stout, 0.5 – 1.5 cm long, densely scaly hairy when young, soon glabrous; laminas subcoriaceous to coriaceous, lacking conspicuous gland dots but punctate on the upper lamina, elliptic to obovate, 10.5 – 19 × 3.5 – 6.5 cm, base cuneate, margin entire, recurved, apex acute to attenuate, glabrous on the upper surface, sparsely lepidote scaly beneath; midrib flat or slightly sunken above, raised beneath; lateral veins 12 – 21 pairs, distinct on both surfaces, camptodromous to brochidodromous; intercostal veins conspicuous

Morphology Reproductive morphology Inflorescences

Inflorescence axillary, racemose, with flowers arranged in a pseudo-umbel at the branch apex; peduncle 5 – 10 mm long, densely pubescent with short rusty hairs; bracts subulate, 2 – 3 mm long, densely pubescent with short rusty hairs, soon caducous

Morphology Reproductive morphology Flowers

Flowers 5 – 9 (–12), white-grey in bud becoming pink-white at maturity; pedicels (4 –) 7 – 10 mm long, elongating to 12 mm after anthesis, densely pubescent with short rusty hairs; calyx-lobes 5, ovate to triangular, 1 – 2 × 2 mm, apex acute, glabrous to sparsely hairy outside, margins ciliate, gland dots orange-brown, inconspicuous and scattered all over; corolla narrowly ovate to narrowly triangular, 4.5 – 7.5 mm long, tube 1.5 – 2 mm, lobes 3 mm wide, long, reflexed, apex acute, glabrous outside, glabrous inside except for short, white to ginger-brown hairy at basal part in the middle, orange-brown gland dots inconspicuous toward the apex; stamens 5, filaments 1.5 – 2 mm long, anthers lanceolate, 3 – 4.5 mm long; ovary ovoid, 1.5 – 2 mm long, distinctly ridged longitudinally, densely pubescent with short ginger-brown hairs, style and stigma 3 – 4.5 mm long, glabrous, distinctly longitudinally ridged

Morphology Reproductive morphology Fruits

Fruit subglobose, 7 – 8 × 7 mm, glabrous; 1-seeded

Note

Similar to other members of Ardisia subgenus Pimelandra in the combination of alternate, distichous leaves with axillary poorly-branched inflorescences with stout peduncles, and reflexed corolla lobes at anthesis, but differing in the coriaceous, elliptic to obovate leaves, with very short peduncles (less than 1 cm long) and, especially, the abaxially glabrous petals with orange-brown inconspicuous glandular dots, and the longitudinally ridged ovary and style. The new species described here is very distinct on account of the combination of the characters useful for subgenus Pimelandra, i.e. the woody habit, entire leaf margins and condensed racemose inflorescences in the axils of normal leaves. The species can be recognised as a member of subgenus Pimelandra in the field by the regularly arranged distichous leaves along the branches, and flowers with open (‘valvate’ — i.e. not overlapping) sepal lobes at anthesis. Specific characters to identify this taxon in addition to the subgenus characters are the coriaceous, elliptic to obovate leaves which are less than 20 cm long, the inflorescence less than 1 cm long with subulate bracts subtending the pedicels, the hairy petals on the inner surface (see Fig. 1G), and hairy ovary. Many species of Ardisia are noted for the black-punctate glands in the leaves and flowers, but in the dry state, A. silamensis has few, if any, distinct punctate glands in the leaves, and orange-brown punctate glands that are very similar in colour to the petals and almost inconspicuous. The specific epithet refers to Mt Silam, and the Latin suffix, “−ensis,” meaning “of origin or place”, referring to the type locality and known distribution of the new species.

Distribution

Malaysia: endemic to Mt Silam, Sabah.

Ecology

Primary forest, mossy forest at the summit with the canopy 20 – 35 ft high; soil grey-brown or red-brown/silty sand in texture/bedrock igneous intrusives.

Conservation

Ardisia silamensis is assessed here as Critically Endangered CR B1ab(iii)c(i, iv) following IUCN criteria (IUCN 2012a, b). The species is currently only known from a single location, and is restricted to habitats on ultramafic substrate and the taxon, unlike other ultramafic-specific taxa such as Nepenthes macrovulgaris, has yet to be collected from similar habitats such as the relatively well-collected ultramafics in the Mt Kinabalu area. The EOO of Mt Silam and its immediate environs is very small at only 25 km2 (surrounding areas not being ultramafic), and the mountain is bounded on each side by roads and associated human habitation along them, with the surrounding forest logged. Currently, whilst we have no recent data on the number of individuals in the population (with no collections since 1992), we have selected the higher category because of the current pressures surrounding the mountain, and the possible changes in habitat quality due to climatic and stochastic events (such as the regular El Niño droughts in the region, see Wooster et al. 2012) that could impact the entire population.