Ardisia patentiradiosa C.M. Hu & Nuraliev, 2021

Nuraliev, Maxim S., Kuznetsov, Andrey N., Kuznetsova, Svetlana P. & Hu, Chi-Ming, 2021, Ardisia patentiradiosa (Primulaceae), a new species from southern Vietnam, Phytotaxa 522 (1), pp. 63-67 : 63-66

Ardisia patentiradiosa C.M. Hu & Nuraliev , sp. nov. ( Figs. 1 & 2 )

TYPE:— Vietnam. Gia Lai Province: K’Bang District, Son Lang Municipality, Kon Chu Rang Nature Reserve , 29 km ESE of Mang Den town, 980 m a.s.l., around point 14°30´50´´N 108°32´46´´E, 05 April 2018, Nuraliev 2017 (holotype MW MW0595717 , isotype IBSC) .

The new species is morphologically similar to A. gracilenta C.M. Hu & J.E. Vidal and A. pitardii C.M. Hu & J.E. Vidal , but differs from both by being glabrous throughout, leaves with pellucid glandular stripes, inflorescence compound umbellate, and with slender pedicels.

Shrubs to 1.5 m tall, glabrous throughout; branchlets ± angulate and slightly dilated at insertion. Leaves alternate, equidistant along the branchlets; petiole 1.5–2.5 cm long, channeled adaxially; blade elliptic-lanceolate, (6) 8–13 cm long, 2–4 cm wide, gradually tapered to the base, apex acuminate, margin entire, thickly chartaceous, adaxial surface dark green, abaxial surface paler and often turning brownish when dry, with scattered translucent glandular stripes (visible under trans-illumination); midrib narrowly impressed above, raised beneath; lateral nerves 11–13 on each side of midrib, with short intermediaters, very slender, indistinct or faint, angle to the midrib about 50°, arcuate upward, not forming an uniform intramarginal vein, reticulation of veins invisible. Inflorescences axillary near apex of branches, compound umbellate; peduncle 2.5–4 cm long; primary rays 2–4, slender, 1–1.8 cm long, almost horizontally spreading out from peduncle, each bearing 2–4 umbellately arranged flowers; pedicels 8–12 mm long, filiform. Calyx whitish green, ca. 1.5 mm long, split nearly to base; lobes broadly ovate, apex broadly acute, tip blunt, margin minutely ciliolate, not punctate. Corolla light purple, ca. 3.5 mm long, rotate, deeply lobed almost to base, lobes broadly ovate, ca. 3 mm long, 2.5 mm wide, apex acute, margin ciliolate towards base. Stamen filaments purple, broadly triangular; anthers narrowly ovate, longer than filaments, ca. 2.5 mm long, apiculate. Ovary superior, ovoid; style protruding beyond stamens, ca. 3.5 mm long; ovules ca. 10, arranged irregularly in 2–3 series on placenta.

Etymology: —The epithet patentiradiosa refers to the widely spreading rays of the umbellate inflorescence of the new species.

Habitat, ecology and phenology: — Ardisia patentiradiosa inhabits a bank of a small forest river. It was found on an islet between two river arms, above a local waterfall. This area represents an outcrop of a basalt bed; it experiences temporary flooding and is overmoistured all year round. Flowering in (March–) April.

Taxonomic remarks: —The new species is assigned to Ardisia subgenus Akosmos Mez (1902: 102), which possesses the following characteristics: erect woody branching shrubs or undershrubs; leaves entire, without marginal glands; inflorescence axillary or sometimes terminal on special lateral flowering branches with a few leaves or leaf-like bracts near apex; sepals not strongly dextrorsely imbricate, acute or obtuse ( Mez 1902, Walker 1940). This subgenus is well represented in SE Asia. According to the available information, the diversity pattern of the subgenus Akosmos is: 18 species in China ( Chen 1979), 13 species in Thailand ( Larsen & Hu 1996), 3 species in the Malay Peninsula ( Stone 1989) . In Vietnam, there are 30 species ( Hu & Vidal 2004), of which 7 species are in common with China, 3 species in common with Thailand and 23 species are endemic. It is thus reasonable for assuming that the greatest concentration of species diversity of subgenus Akosmos occurs in Vietnam.

Ardisia patentiradiosa is characterized by the following combination of taxonomically important features: plant glabrous throughout, leaves with pellucid glandular stripes, inflorescence compound umbellate with primary rays spreading widely and almost at right angle to peduncle, pedicels very slender, up to 1.2 cm long. It is therefore readily distinguished from the species with hairs or scurfy scales on branchlets or inflorescence, including A. gracilenta and A. pitardii that are otherwise very similar to A. patentiradiosa (Table 1). Among the glabrous species, only A. obtusa shows some similarity with the new species in general form and leaf shape, but A. obtusa can be easily distinguished by its subterminal inflorescences borne in axils of reduced leaves, paniculate pattern in inflorescence branching (i.e., branches corymbosely or umbellately arranged), and leaves without pellucid glandular dots or stripes.

Table 1. Main morphological differences between A. patentiradiosa and its allies.

Figures

FIGURE 1. Ardisia patentiradiosa. A. flowering branch; B. a flower after removing corolla and stamens, showing calyx and pistil; C. pistil; D. flower; E. corolla opened up, showing stamens.A–E drawn from Nuraliev 2017.

FIGURE 2. Ardisia patentiradiosa.A. flowering branch; B. inflorescence; C. abaxial leaf surface; D–E. flowers; F.dorsal view of a flower showing calyx.