Billolivia citrina Luu, H.Đ.Tr

Trư ờng, Lưu H ồng, Đăng, Tr ần H ữu, Nhân, Ph ạm H ữu, Trung, Nguy ễn Tr ần Qu ốc, Đ ạt, Nguy ển Qu ốc & Long, Vũ Ng ọc, 2018, Two new species of Billolivia (Gesneriaceae) with yellow flowers from Vietnam, Phytotaxa 362 (2), pp. 227-232 : 227-229

Billolivia citrina Luu, H.Đ.Tr ần et N.L.Vu, sp. nov. ( Fig. 1 )

Billolivia citrina is similar to B. yenhoae in having yellow flowers but differs in having ovate leaves, much shorter inflorescences, smaller flowers, citrus yellow corolla lobes, slightly curved filaments and apically hairy ovary. It is also close to B. cadamensis in having overall habit, leaf indumentum, flower shape, and purple lines on the base of lobes but differs in having ovate leaf laminae, densely pubescent bracts, greenish white calyx, and yellow corolla lobes.

Type:— VIETNAM. Phú Yên Province: Sông Hinh District, Mt. Hòn Đen, approximate coordinates 12°53’52”N and 108°48’40”E, at ca. 600 m elevation, 20 January 2017, Trần H ữu Đăng, Nguyễn Trần Quốc Trung, Nguyễn Quốc Đạt, Vũ Ngọc Long NF-BOL-PY 002 (holotype SGN!, isotypes SGN!, PHH!, HNU!, VNMN!).

Terrestrial herb to 20 cm tall; stems rhizomatous, creeping and then erect, sparsely pubescent with brown multicellular uniseriate hairs to 3 mm long. Leaves alternate; petioles 3‒9 cm long, densely pubescent with brown multicellular uniseriate hairs to 3 mm long; lamina ovate, slightly asymmetric, 9‒14 cm long, 5.0‒9.0 cm wide, base round, apex subacute, margin coarsely dentate, 8‒10 secondary veins on each side of midrib, adaxial lamina dark green, glabrous, margin densely ciliate, abaxial lamina pale green, with dense brown appressed hairs to 2 mm long. Inflorescences axillary, 3‒9-flowered; peduncle white, to 8 mm long, densely pubescent; ray white, to 1 mm long, densely pubescent; bracts lanceolate to narrowly triangular, to 9 × 3 mm, abaxially densely pubescent, apex acute, margins ciliate; pedicels white, 2‒2.5 cm long, distally sparsely pubescent, basally densely pubescent. Calyx of 5 lobes almost divided to base, greenish white, outside densely long brown pubescent, inside glabrous; lobes triangular, to 8 mm long, to 3 mm wide at base, apex acute, with ciliate margins. Corolla 26‒28 mm long, composed of a narrow tube which slightly flares towards an oblique mouth and a 2-lipped limb with lobes recurved; tube 14 mm long, white, outside pubescent, inside glabrous; throat white, with shortly stalked to subsessile glands and purple lines on the base of lobes; upper lip 2- lobed, lobes 6−7 × 12−13 mm, ovate; lower lip 3-lobed, lateral lobes elliptic, 5−6 × 10−11 mm, lower lobe slightly obovate, 7−8 × 5.5−6 mm; all lobes citrus yellow, outside sparsely pubescent with multicellular uniseriate hairs, inside with shortly stalked glands. Stamens inserted at 6‒7 mm from corolla base; filaments slightly curved, 7‒8 mm long, white with a red dot in the middle, sparsely glandular puberulent. Disc bowl-shaped, 5-lobed at apex, 1 mm high. Ovary 3‒3.5 mm long, 2 mm in diameter, with dense stalked glands on apical 1/3; style 7‒8 mm long, densely covered with glandular hairs; stigma slightly lobed, ciliate. Fruits ovoid, greenish cream, 14−16 × 6−8 mm, mostly brown puberulent, basally glabrous, translucent when ripe; seeds many, ovoid, 0.15 × 0.2 mm, black.

Distribution, habitat, and phenology: — Found on moist gulleys in montane moist evergreen closed forest at around 600 m in elevation, Mt. Hòn Đen, Sông Hinh District, Phú Yên Province, Vietnam. Flowering and fruiting were seen in December and January.

Etymology: — The epithet refers the citrus yellow colour of its corolla lobes.

Vietnamese name: — LƯu hoa vàng chanh.

Proposed IUCN conservation status: — Billolivia citrina has been known only from the type location, where it is not commonly encountered. Our surveys in the province over the last several years have not found additional populations of the species. This new species appears to have a restricted distribution confined to forests of Song Hinh District with a total area of <400 km 2 where deforestation for agricultural expansion is occurring. The species, therefore, should be considered for listing in the Endangered category, EN B2a&b(i&ii) ( IUCN 2012).

Notes:— Billolivia citrina is similar to B. yenhoae in having yellow corolla lobes but differs in many characters: ovate leaves, much shorter peduncles, smaller flowers, citrus yellow corolla lobes, slightly curved filaments, and apically hairy ovaries. Billolivia citrina is also morphologically close to B. cadamensis in having short stems, glabrous adaxial laminae, hairs mainly on abaxial midribs and veins, calyces divided into 5 lobes to base, shape of corolla and lobes, corolla throat with purple lines on the base of lobes and white glandular puberulent filaments with a red dot in the middle. The later species, however, has elliptic leaf laminae, glabrous bracts, brownish red calyces, and white corolla lobes. The purple lines in the corolla of B. citrina recall those of B. cadamensis , B. tichii , B. vietnamensis , and B. moelleri but these species have white and/or purple corolla lobes.

Figures

FIGURE 1. Billolivia citrina. A. Habit. B. Stem and inflorescence. C. Flower and fruits. D. Flower, side view. E. Lower lip of corolla. F. Stamens. G. Upper lip of corolla and gynoecium. H. Leaf, abaxial and adaxial laminas. I. Infructescences. J. Fruit, cross and longitudinal sections. Photo: Trần Hữu Đăng.