Three new plant species discovered in Nui Chua National Park, Ninh Thuan, Vietnam

Morphological characteristics and taxonomy

1. Memecylon longipedunculatum Tagane , VSDang & Nuraliev - Long-stemmed Sam, belongs to the Mua family (Melastomataceae), is a small tree, up to 5 m high. Leaves grow opposite, small, thick, slightly succulent, obtuse apex or sometimes concave, midrib slightly raised on the underside. Flowers are small, blue-purple, growing in clusters at the ends of branches or leaf axils; calyx is bell-shaped, petals are broadly triangular, pointed tip. Berries, spherical, purple-black when ripe.

Memecylon longipedunculatum Tagane, VSDang & Nuraliev - Long-stemmed Sam (Photo: Shuichiro Tagane)

M. longipedunculatum has many similarities with M. chevalieri, which is found in Cambodia, Laos and Vietnam. However, the new species differs in having longer flower stalks and petals, smaller leaves and spherical fruits.

The new species was published in the specialized journal Phytotaxa, No. 683, pp. 1 - 8, January 29, 2025 - https://doi.org/10.11646/phytotaxa.683.1

2. Nymphanthus adenophorus Tk.Yamam ., Tagane & VSDang - Phyllanthus adenophorus, belonging to the Phyllanthaceae family, is a low, creeping, monoecious shrub; branches are reddish brown. Leaves are arranged alternately, leaf blades are obovate to broadly elliptical, sometimes nearly round, grayish red when young, turning green when mature. Flowers grow in leaf axils, monoecious; male flowers grow singly or in bunches, pink to purple; female flowers grow singly, purple. Capsules, nearly spherical, purple, smooth.

Nymphanthus adenophorus Tk.Yamam., Tagane & VSDang - Phyllanthus amarus (Photo: Shuichiro Tagane)

This species has similar morphological characteristics to N. pireyi - a species endemic to Vietnam and N. nanellus - a species endemic to China, but the difference is that the flower-bearing branches are shorter, the number of leaves is fewer, the leaf blades are larger, the male flower stalks are longer and the female flowers have multi-layered folded discs.

The new species was published in the specialized journal Phytotaxa, No. 683, pp. 18 - 24, January 29, 2025 - https://doi.org/10.11646/phytotaxa.683.1

3. Wrightia nuichuaensis Tagane & VSDang - Long cac nui chua, belongs to the Apocynaceae family, is a shrub about 3m high, with a smooth stem and white latex; young branches are yellowish brown to reddish brown, shiny, old branches turn gray with small rough spots. Leaves grow opposite, elongated elliptical or inverted elliptical, dark yellowish green on the upper surface, dull yellowish brown on the lower surface, both sides are smooth and shiny. The inflorescence grows at the top of the branch, cyme-like, bearing 3 - 13 flowers, drooping flower stalks when blooming; Green calyx, 5 pointed lobes, edges with short hairs; Orange - red corolla, wide ovoid lobes, edges slightly curved and inverted when fully blooming, the outer surface has a characteristic layer of small seeds.

Wrightia nuichuaensis Tagane & VSDang - Lord Mountain Cucumber (Photo: Shuichiro Tagane)

With its orange-red flowers, twisted corolla, stamens high in the corolla tube and simple appendages, this species is easily distinguished from other species in the genus Wrightia.

The new species was published in the specialized journal Phytotaxa, No. 683, pp. 87 - 90, January 29, 2025 - https://doi.org/10.11646/phytotaxa.683.1

Distribution and conservation range

The three newly discovered plant species all have a narrow distribution range, mainly limited to the Nui Chua National Park (Ninh Thuan), one of the important ecological regions of Vietnam. In particular, Memecylon longipedunculatum Tagane, VSDang & Nuraliev were also found on Hon Tre Island (Khanh Hoa), which has a typical coastal ecosystem; this species usually grows at an altitude of less than 200 m, in sparse coastal forests on sandy or laterite soils with poor nutrients, affected by drought conditions and the marine environment.

Meanwhile, Nymphanthus adenophorus Tk.Yamam., Tagane & VSDang and Wrightia nuichuaensis Tagane & VSDang are currently only recorded in Nui Chua National Park. N. adenophorus grows in coastal scrubland at an altitude of 25 m, with an estimated population of about 50 individuals; while W. nuichuaensis grows in evergreen broadleaf forests on granite soil, with less than 20 mature trees recorded. Both species are proposed for conservation according to the criteria of the International Union for Conservation of Nature (IUCN) (2024).

Associate Professor, Dr. Dang Van Son said: Up to now, Nui Chua National Park has recorded 1,514 species belonging to 596 genera of 147 families of vascular plants. Among them, many new species have been described since 2000 by domestic and international botanists. This shows that continued investigation, statistics and taxonomic research are necessary to better understand the arid flora of this area. The discovery of 3 new plant species not only expands the national flora list but also shows great potential in discovering and publishing many more species that have never been recorded in the area and neighboring areas. Due to their narrow distribution range, these new species are facing a serious threat. Therefore, further research on ecology, distribution and timely conservation measures are urgent, to protect not only new species but also existing rare plant species from environmental and human impacts.

Associate Professor, Dr. Dang Van Son (second from right) and the field research team at Nui Chua National Park, Ninh Thuan

Translated by Quoc Khanh
Link to Vietnamese version