Premna confinis Pei & Chen ex Wu, Fl.

Premna confinis Pei & Chen ex Wu, Fl. View in CoL Yunnan. 1: 437 (1977).

Type: — CHINA. Yunnan. Funing County, in mixed forests, elev. 600 m, 13 May 1940, Q.W.Wang & Y.Liu 87177 (Holotype KUN0484498 !, isotypes KUN0484499 !, PE00031067 !, WUK0276533 !)

Illustrations:— Wu (1977: 438, Plate 104: 1–2); Pei & Chen (1982: 92, Plate 10: 1–4); Wu & Peter (1998: 49, Fig. 49: 1–4).

Phenology: —Flowering buds were observed in early April, while flowers and fruits were recorded from mid-April to late May.

Distribution and habit: —In China, populations of P. confinis are currently known only from western and northern Guangxi and southeastern Yunnan, where they typically occur in secondary forests on limestone mountains ( Pei & Chen 1982, Chen & Gilbert 1994). In Vietnam, the species has recently been recorded in Cao Bang and Ha Giang provinces, which are also found in karst forest habitats. All these new localities lie along the China-Vietnam border ( Fig. 3 View FIGURE 3 ). In Cao Bang Province, the species was found in primary mixed forests dominated by Keteleeria fortunei ( Murray 1862: 421) Carrière (1866: 449) , situated on limestone ridges at elevations of 600–1000 m. In Ha Giang Province, it grows in secondary evergreen broad-leaved forests on limestone mountains at altitudes ranging from 1200 to 1280 m.

Taxonomic note: —The taxonomic study of Premna in Vietnam originated from Paul Dop's fieldwork in the Indochina region during the early 20th century. In 1923, only three species and one variety of Premna were initially recorded in Vietnam ( Dop 1923). Among these, P. balansae and P. chevalieri , were collected from the Tonkin region in northern Vietnam. Following extensive fieldwork over several decades, Pham (2003) published the first comprehensive list of Premna species in An illustrated Flora of Vietnam, documenting 15 species and one variety. A thorough revision of Premna was conducted in the updated Flora of Vietnam, which recognizes 25 species and four varieties ( Vu 2007). Subsequently, an additional new species, P. vietnamensis Li in Hai et al. (2018: 5), was discovered from Gia Lai Province, Central Highlands of Vietnam. This discovery highlights the existence of previously unrecognized biodiversity within the genus, as demonstrated by our current findings. Originally, P. confinis had been misidentified as P. chevalieri at the Missouri Botanical Garden Herbarium. Upon closer examination, it was correctly identified as P. confinis . Key morphological differences distinguish the two species: P. confinis features large, leathery leaves with an oblong-lanceolate shape and sunken veins, an unequally five-lobed calyx, and purplish-red fruit. Conversely, P. chevalieri has papery, glossy leaves that are ovate to elliptic in shape, a calyx with five equal shallow lobes, and black fruit. Through field and herbarium works, this study formally confirms the presence of P. confinis in Vietnam. This discovery enhances our understanding of Premna diversity in the country and emphasizes the need for ongoing taxonomic studies across the Indo-China region.

Specimens examined: — CHINA. Guangxi: Dahua County, Liuye Town , 468 m, 24 April 2018, D.X.Nonget al. 451229180424035LY ( GXMG0181787 !) ; Debao County, Longguang Town , broad-leaved forest, 591 m, 26 June 2015, Debao Team 451024150626015LY ( GXMG0175284 !) ; Jingxi County, Dizhou Town , 850 m, 21 April 1998, H.N.Qin et al 1028 ( PE02009750 !) ; Lingyun County, Jiayou Town, broad leaves forest, 933 m, 29 April 2013, Lingyun Team 451027130429057 ( GXMI056957 !) ; Longya County, broad leaves forest, 1016 m, 16 May 2012, K.J.Yan 19894 ( GXMI062064 !) ; Longzhou County, Jinglong Town , 500 m, 14 August 1957, S.Q.Chen 13970 ( IBSC0496393 !) ; Napo County, Baisheng Town, Mianliang Village , 9 May 2015, G.X.Hu et al. 276 ( KUN1265974 !) ; Nonggang National Nature Reserve , 590 m, 27 April 2009, Y.S.Huang & C.W.Wang H09354 ( IBK00216764 !) ; Tian-e County, Liupai Town, 900 m, 11 May 1989, Beijing team 891162 ( PE02009752 !). Yunnan: Xichou County, 1200 m, 24 December 1939, Q.W.Wang & Y.Liu 85966 ( PE01276403 !) ; Pingbian County, 15 June 1953, 1030 m, P.Y.Mao 2912 ( IBSC0496397 !) . VIETNAM. Cao Bang: Tra Linh District, Quoc Toan Municipality, in Thang Heng and Lung Tao villages near Thang Heng Lake , 650–1000m, 22°45'30"N, 106°17'22"E, 25 May 1997, L.Averyanov, VH4960 ( MO5319638 !) GoogleMaps ; ibid., L.Averyanov, VH 4896 ( MO5287752 !) GoogleMaps ; Nguyen Binh District, Ca Thanh Municipality, Ta Pin village , 22°43'47"N, 105°51'24"E, 1250–1350 m, 17 April 2019, K.S.Nguyen et al. NSK 1275 ( HN!) GoogleMaps ; Ha Giang: Meo Vac District , 23°10'27"N, 105°22'25"E, 1200–1280 m, 6 April 2024, B.H.Quang et al. BHQ 1086 ( HN!) GoogleMaps .