Parnassia aff. procul H. Turner & Veldkamp (2001: 601)

Pham, Ngoc Hoai, Ren, Ming-Xun, Nuraliev, Maxim S., Trinh, Ngoc Bon, Nguyen, Tien Dat, Ragupathi, Gopi & Pham, Van The, 2022, The genus Parnassia in Vietnam, and a checklist of Vietnamese Celastraceae, Phytotaxa 536 (3), pp. 213-227 : 220-221

2. Parnassia aff. procul H. Turner & Veldkamp (2001: 601) ( Fig. 5 )

Specimen examined: — VIETNAM. Lam Dong Province: Lac Duong District, Langbian Mountain , near summit, grassland area in evergreen forest, around point 12°01.879’N 108°24.759’E, at an elevation of 1847 m a.s.l., 5 September 2018, Pham Van The, Vo Duc Quang PVT1027 (photos LE: LE01093239 http://en.herbariumle.ru/?t=occ&id=99498) .

Phenology: —Flowering and fruiting in August–September.

Habitat and ecology: —The species grows in an open place near the mountain summit. The area is covered with a pine forest; the forest floor is inhabited by various ferns, Poaceae and Melastomataceae .

Brief description and notes: —The population recently discovered in mountains of Lam Dong Province is insufficiently known, but quite distinct morphologically. It is characterized by broadly cordate basal leaves, floriferous stem with a single cauline leaf inserted approximately at its middle, almost entirely white petals (only very slightly greenish at base adaxially) divided into claw and blade, obovate-rhomboid petal blade, triangular petal apex, fimbriate petal margin with fimbriations of short to medium length, anther connective without apical projection, and conspicuously three-lobed staminodes with subequal slightly thickened lobes.

The plants in question do not correspond to any of the species included in the treatment of Parnassia in «Flora of China » ( Gu & Hultgård 2001). The keys provided by Gu & Hultgård (2001) lead to P. epunctulata J.T. Pan (1985: 220) endemic to NW Yunnan, from which the Lam Dong plants differ in several traits including broader basal leaves and uniformly subequal (vs. sometimes unequal) staminode lobes. Within the preliminary account of Parnassia in Thailand ( Suksathan 2009), P. mysorensis B.Heyne ex Wight & Arnott (1834: 35) is described to have a broad variation, so that the Lam Dong plant appears to fit within the concept of this species. However, the concept proposed by Suksathan (2009) contradicts the description of P. mysorensis by Gu & Hultgård (2001): in the latter treatment, P. mysorensis is stated to possess entire, erose, or serrate (but not fimbriate) petal margin, which prevents assignment of the Lam Dong plant to this species.

The record Pham Van The, Vu Dinh An PVT1027 is remarkably similar to P. procul in the majority of vegetative and floral traits, including leaf shape, shape of petal margin and staminode morphology ( Turner & Veldkamp 2001, see also De Wilde & Duyfjes 1994). The Lam Dong plant differs from P. procul in obovate-rhomboid (vs. spathulate) petals with triangular and more or less acute (vs. obtuse to truncate) apex; however, this difference can possibly be a manifestation of an infraspecific variation. A significant variation of petal shape is already known, for example, in P. wightiana ( Gu & Hultgård 2001) .

Taking all these arguments into account, we provisionally assign Pham Van The, Vu Dinh An PVT1027 to P. procul , a species hitherto known only from Mount Leuser in northern Sumatra ( Turner & Veldkamp 2001). This finding represents a second species of Parnassia recorded in the flora of Vietnam. We argue that a comprehensive investigation of this population, including molecular phylogenetic studies, is needed for further clarification of its identity. In addition, a broad-scale morphological and phylogenetic revision of Asian tropical and subtropical Parnassia is required in order to better understand species boundaries in this genus, and make the species identification more straightforward.

Figures

FIGURE 5. Parnassia aff. procul. A, B. Plants with flowers and young fruits. C, D. Flowers at late anthesis (with anthers abscised), top views. Pham Van The, Vo Duc Quang PVT1027. Photos by Vo Duc Quang.