Ardisia nagaensis Julius, T. Kajita & Utteridge, 2020

Julius, Avelinah, Kajita, Tadashi & Utteridge, Timothy M. A., 2020, Two new species of Ardisia subgenus Tetrardisia (Primulaceae - Myrsinoideae) from Borneo, PhytoKeys 145, pp. 139-148 : 139

Ardisia nagaensis Julius, T. Kajita & Utteridge sp. nov. Figure 2

Diagnosis.

Similar to Ardisia tetrasepala in its simple and compact inflorescence with corymbose flowers but differs mainly vegetatively in having leaves laxly arranged, longer petioles that are covered with glandular hairs, a chartaceous lamina without marginal secondary veins, surface with scattered stellate hairs near the margin beneath and leaf base obtuse or ± cuneate. The corolla lobes are smooth without lepidote scales (vs. lepidote scales present in A. tetrasepala ).

Type.

MALAYSIA. Borneo: Sarawak, Tatau District, Ulu Merirai, Gua Naga, [02°39 ’12” N, 113°03 ’05” E], 11 July 2005, Julia et al. S95726 (holotype KEP!; iso: SAR, SING)

Description.

A small shrub, less than 1 m high; stems glabrescent, slightly flexuous, winged between the nodes with obscure raised lines running along the internodes between the petiole bases. Indumentum of simple, short (stalked), glandular, or stellate (star-liked), pale brown to rusty hairs (visible under microscope). Leaves alternate; petioles 1.5-3 cm long, sparsely to densely hairy towards midrib, simple, short, glandular hairs; lamina chartaceous, with dense gland-dots throughout the leaf, glabrous on both surfaces except for margin with scattered stellate hairs beneath, elliptic-lanceolate, 17-19 × 5-5.5 cm, apex long acuminate and slightly caudate with acumen 1.5-2.0 cm long; base obtuse or ± cuneate, margin obscurely denticulate being entire in appearance, midrib flat or slightly sunken above, raised beneath, glabrous except hairy with glandular hairs beneath, denser near leaf base; lateral veins 13-15 pairs, distinct above, prominent beneath, inter-secondary veins present in between; intercostal veins percurrent, distinct beneath. Inflorescence terminal on lateral branches, simple with flowers arranged in corymbs; peduncle and rachis 4-5 cm long, densely hairy with glandular hairs; bracts ovate to elliptic, 0.5-1.5 mm long, hairy with glandular hairs. Flowers ca. 24; pedicels slender, 1.2-1.8 cm long, up to 2 cm long in fruiting, covered with dense, glandular hairs; calyx-lobes 4, purplish, gland-dotted, lacking hairs, broadly ovate, 1-1.5 × 1-1.5 mm, apex obtuse, margin incised, sparsely ciliate with short, thick hairs; corolla-lobes 4, reflexed, twisted apically, purplish with transparent margin, lanceolate, ca. 8 × 2.5 mm, glabrous on both surfaces; stamens 4, spreading upright (in open flower), filament ± sessile, anthers twisted apically, lanceolate, ca. 6 × 1 mm, apex without a prolonged hyaline tip, thecae opening by longitudinal slits, with lineate, black dots behind, glabrous; ovary globose, ca. 1 × 0.8 mm, style and stigma filiform, ca. 6 mm long, ovules 4-6 in 1-series. Fruits ripe bright red, globose, ca. 6 × 5 mm.

Distribution.

Endemic in Borneo, Sarawak; known only from Gua Naga, Ulu Merirai area, Tatau District.

Etymology.

Ardisia nagaensis is very local and was found at only one locality, Gua Naga, for which it is named.

Conservation status.

Data deficient (DD). The only specimen available was collected in 2005 and the species is known only from a single collection location from Ulu Merirai in Central Sarawak, and thus meets the B1a criterion for Critically Endangered (CR) status. The Ulu Merirai region is an area of sandstone with limestone cliffs, and supports several point endemics, including several newly described species of Begonia L. ( Kiew and Sang 2009) and Monophyllea R. Br. ( Kiew and Sang 2013). The species was found outside of any protected area, but satellite imagery in Google Earth from 2017 shows that the collection locality has undisturbed forest coverage and was not penetrated with roads or logging tracks. However, lack of collections and field observations of the species do not allow inference of decline or fluctuation in population size or EOO and AOO, and we are unable to fulfil the criteria to preliminary assess this species as Critically Endangered.

Notes.

Compared to the other members of subgenus Tetrardisia , this new species described here has an affinity with A. tetrasepala , endemic to Peninsular Malaysia [Johor, Gunung Pulai]. This is because both are characterized by a simple and compact inflorescence, whereas other taxa in x Tetrardisia have compound and laxly flowers arranged. Ardisia nagaensis differs from A. tetrasepala by the leaf characters viz. the petiole length ( A. nagaensis with 1.5-3 cm long vs. A. tetrasepala with 0.5-0.8 cm long), the leaf base ( A. nagaensis with obtuse or ± cuneate leaf base vs. A. tetrasepala with cordate-rounded) and the venation ( A. nagaensis without marginal secondary veins vs. A. tetrasepala with marginal secondary veins). Further morphological comparison between these two species is given in the Table 1 .

The calyx is described as ‘purplish’ in the specimen label which probably refers to both the calyx and corolla. The corolla margin on one side is transparent as observed in A. denticulata .

Figures

Figure 2. Ardisia nagaensis Julius, T. Kajita & Utteridge, sp. nov. A habit B glandular hairs on stem C erect, simple hairs on petiole D the venation close-up E stellate hairs close-up F enlarged inflorescence G flower bud H mature flower I open calyx J open corolla with stamen K corolla lobe L stamen, front and back view M placenta and ovules. (Drawn by Mohamad Aidil Noordin from Julia et al. S 95726).