Pottingeria acuminata Prain

Bon, Trinh Ngoc, Savinov, Ivan A., Ha, Do Thi Thanh, Zimmer, Heidi, Son, Nguyen Thanh & Son, Hoang Thanh, 2023, Pottingeria acuminata Prain (Celastraceae): A new generic and species record for the flora of Vietnam, Phytotaxa 606 (3), pp. 220-224 : 222-223

Pottingeria acuminata Prain : J. Asiat. Soc. Bengal, Pt. 2, Nat. Hist. 67: 291 (1898).

Literature: —Airy Shaw, D.F. Cutler & S. Nilsson, Kew Bull. 28: 97. 1973; M.P. Simmons in Kubitzki, Fam. Gen. Vasc. Pl. 6: 61. 2004; L.B. Zhang & M.P. Simmons, Syst. Bot. 31: 122. 2006; Hou et al. Fl. Thail. 10(2): 185–186. 2010.

Basionym: — Pottingeria acuminata Prain (1898: 291)

TYPE: — Upper Burma ( MYANMAR): Pottinger s.n. (type: K: K000687024 ) Figs 1–2 .

Shrubs or trees, glabrous. Stipules small, triangular. Leaves alternate, distichous, margin entire, venation basally strongly triplinerved (acrodromous), secondary nerves not distinct. Inflorescences axillary, narrowly thyrsoid paniculate, sometimes several together. Flowers small, bixexual, 5-merous. Calyx deeply 5-lobed. Petals erect, longer than calyx lobes. Disk annular, somewhat 5-lobed, fleshy, thin, intrastaminal. Stamens 5, attached to the edge of the disc, filaments linear, anthers opening intro-latrorse with lengthwise slits. Ovary 1-locular, 3-carpellate, smooth, with an intruded parietal placentation with numerous ovules. Fruits capsular, ovoid, septicidally dehiscent. Seeds numerous, narrowly fusiform, albuminous.

According to Airy Shaw et al. (1973: 100), there are two varieties of P. acuminata — var. latifolia Airy Shaw ( Thailand: Chiang Mai, Doi Nang Ka)—leaves elliptical or widely ovate, 11 cm long and 6 cm wide and typical var. acuminata (Assam, Upper Myanmar)—leaves 6−9 cm long and 2−4 cm wide. Our specimens belong to var. acuminata .

Distribution, ecology and habitat in northern Vietnam:

Pottingeria acuminata has been found at Muong La nature reserve; Hua Trai commune, Muong La district, Son La Province. They usually occur at the edge of secondary forests. Pottingeria acuminata live together with species such as: Litsea cubeba , Trema orientalis , Eurya acuminata, Schima wallichi, Sonerila cantonensis , Imperata cylindrica and Gleichenia linearis .

Specimen examination: VIETNAM. Muong La nature reserve, Hua Trai commune, Muong La district , Son La Province. 21°37’24.08»N, 104°23’55.12»E, 1825 m elevation. on the edge of secondary forest, 20 November 2020, flowers and fruits, Trinh Ngoc Bon SCU2020-005 (VAFS!)

Taxonomic relationships

Pottingeria is an interesting and unusual woody genus of Flowering plants, which taxonomic position was undetermined for a long time. It was originally described by Prain in 1898 (Prain, 1898) on the solitary specimen from Upper Burma (coll. Pottinger), but without details of flower structure and was placed within Saxifragaceae . Airy Shaw et al. (1973: 100) consider Pottingeria genus as separated subfamily Pottingerioideae Airy Shaw in Celastraceae family, although still A. Engler (Engler et Prantl, 1930) posited it taxon defined as Saxifragaceae —Escallonioideae—Pottingerieae Engler (1930: 111). A. Takhtajan (1987) separated genus Pottingeria in monotypic family Pottingeriaceae Takht. (1987: 212) and nested it in Hydrangeales. Palynologically the genus closely related to Saxifragaceae s.l. or Hydrangeaceae ; on wood anatomy—to Escalloniaceae ; on seed structure—to Cunoniaceae (see review in Zhang & Simmons, 2006). Finally, according to molecular analysis, the genus «appears to be part of an early derived lineage within the Celastraceae ». Pottingeria seemingly forms a basal clade within the Celastraceae . The analysis do not support or refuse its recognition as a separate subfamily ( Zhang & Simmons, 2006).

Figures

FIGURE 1. Pottingeria acuminata Prain. A: Flowering shoot. B: Inflorescence. C: Leaf top view. D: Leaf bottom view. E: Flower. F: Immature fruit. G: Fruiting shoot. A–D, G: scale bar 1 sm; E–F: scale bar 1 mm. Photos Trinh Ngoc Bon.

FIGURE 2. A new locality of Pottingeria acuminata Prain in Vietnam (red star) and other countries according to literature sources plus herbarium materials (yellow stars) (map).