Rungia gialaiensis D. V. Hai, Z. L. Lin & Joongku Lee 2021, sp. nov.

Rungia gialaiensis D.V.Hai, Z.L.Lin & Joongku Lee, sp. nov. (Figs. 2–3)

Type:— VIETNAM. Gia Lai Province, Kbang District, Dak Smar Commune, 640 m asl., 14°13'11.9"N, 108°36'17.4"E, 7 April 2018, D. V. Hai and S. D. Thuong, DVH-100 (HN!). (holotype HN!; isotypes HN!, IBSC!).

Perennial stoloniferous herbs, usually 1 to 3 branched grown from leaf axils, spreading on the ground and rooting at nodes, spreading branches 10–30 cm long; flowering branches erect, up to 20 cm tall, stems short, up to 5 cm long, quadrangular when young; subterete, sulcate, bifariously retrorsely pubescent. Leaves opposite, usually isophyllous; petiole 1.5–2.5 cm long, pubescent; blades oval to ovate, obovate, 3.5–6.5 × 2.5–4.5 cm, base rounded and sometimes slightly decurrent onto petiole, margin entire and ciliate, apex obtuse to rounded, adaxially pubescent, green, abaxially pubescent, densely along the midvein and secondary veins, pale green, sometimes purple; both surfaces covered with cystoliths; secondary veins 6–7 on each side of midvein, netted near the margin. Spikes terminal, 5–7 cm long, secund; peduncle 2–3 cm long, pubescent, rachis pubescent. Bracts 4-ranked, heteromorphic, 2 ranks fertile and 2 ranks sterile; sterile bracts rhombic, 6–6.5 × 2–3.0 mm, green and purple on veins, 3 pair secondary veins, pubescent on both surfaces, margin membranous hyaline, 0.1–0.7 mm wide, hyaline toward the apex, margin ciliate, apex caudate to 2 mm long; fertile bracts lanceolate to narrowly elliptic, 7–7.5 × 1.5–2.0 mm, green and purple on veins, 3 pair secondary veins, pubescent on both side, margin membranous hyaline for 0.1–0.5 mm wide, hyaline toward the apex, margin ciliate, apex caudate to 1–1.5 mm long. Bracteoles narrowly lanceolate to linear, 4.5–5.5 × 0.7–0.9 mm, pale green– purple, pubescent, margin membranous for 0.1–0.3 mm wide, margin ciliate, apex caudate to 1–1.5 mm long. Calyx 5-lobed almost to the base, lobes equal, linear, 4.5–5 × 0.3–0.4 mm, pubescent, margin ciliate, apex acuminate. Corolla 10–12 mm long, white with purple stripes or bluish, bilabiate; tube cylindrical, ca. 4 mm long, glabrous at base and puberulous near throat; upper lip 2-lobed, puberulous, lobes triangular; lower lip 3-lobed, lobes ovate-rounded, apex rounded, the middle one larger than the lateral ones, puberulous. Stamens 2, inserted at base of corolla throat and base adnate with corolla tube; filaments 3–4 mm long, glabrous; anthers bithecous, superposed, thecae ovoid, the upper one sparsely pubescent and muticous, the lower one sparsely pubescent and spurred at base. Disc annular. Ovary glabrous, ca. 1 mm long, 2-loculed with two ovules per locule; style 5–6 mm long, pubescent at base and less at nearly the top; stigma minutely 2-lobed. Capsule clavate, 6–7 × 2 mm, stipitate, pubescent, 4-seeded. Seeds suborbicular or orbicular in outline, compressed, 1.1–1.2 × 1.1 mm, glabrous, surface verrucose.

Etymology:— The species is named after the type locality, Gia Lai province in Vietnam.

Phenology:— Flowering: August–March, fruiting; September–April.

Distribution and ecology: — Rungia gialaiensis is currently known from Kbang District, Gia Lai Province, and probably endemic to the Central Highlands. It was found growing under the shades of secondary forests on the basaltic soil of the hillocks, at an elevation of around 640–650 m asl. Alpinia sp., Gomphostemma lucidum Wall. ex Benth. (1831: 12), Phoebe paniculata (Nees) Nees (1836: 105), Piper sp., Rinorea virgata (Thwaites) Kuntze (1891: 42) were found associated with the new species.

Conservation status:— During our investigation in this area, we could observe only a few scattered populations of Rungia gialaiensis growing on soil under secondary forests. Because of its narrow distribution with an estimated population size of <1000 individuals, it is assessed to be Vulnerable (VU) based on the IUCN Red List Criteria (IUCN 2017). Further inventories are needed to find additional populations in Vietnam.

Additional Specimens Examined (Paratypes):— Vietnam. Gia Lai Province, Kbang District, Dak Smar Commune, 640 m asl., 14°13'11.9"N, 108°36'17.4"E, 14 March 2011, T. T. Bach, D. V. Hai, B. H. Quang, H. M. Tam, S. D. Thuong, PTV 714 (HN!); ibid. 650 m asl., 14°13’30.9”N, 108°36’18.2”E, 12 August 2011, T. T. Bach, D. V. Hai, B. H. Quang, H. M. Tam, S. D. Thuong, PTV 1026 (HN!); ibid. 640 m asl., 14°13’11.9”N, 108°36’17.4”E, 22 November 2013, D. V. Hai, B. H. Quang, DVH22112013-1 (HN!).

Taxonomic Notes:— The spike of Rungia gialaiensis is secund, with only one fertile bract at each node of the spike and the bracts being heteromorphic. Therefore, this new species should be placed in Rungia sect. Rungia following Gao & Deng (2017). The new species resembles R. daklakensis at first glance in the flowering branches and leaf shape (Hai et al. 2016), but differs from the latter mainly by the presence of stolons, characters of bracts (rhombic, pubescent and ciliate margin in R. gialaiensis versus oblong to obovate-elliptic and glabrous in R. daklakensis) and corolla (upper lip 2-lobed in R. gialaiensis versus unlobed in R. daklakensis). Close scrutiny of the inflorescences suggests R. gialaiensis allied to R. khasiana T.Anderson (1876: 518) because of the similarity in the characters of bracts, corolla and fruit, which are critical in identifying a Rungia species. R. gialaiensis, however, differs from R. khasiana mainly in the habit (erect flowering branches up to 20 cm tall in R. gialaiensis versus decumbent, 15–30 cm tall branches in R. khasiana), presence of stolons, and much shorter stem. The morphological comparison between R. gialaiensis, R. daklakensis and R. khasiana is shown in Table 1.