Billolivia yenhoae Luu, 2018

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 : 229-231

Billolivia yenhoae Luu , sp. nov. ( Fig. 2 )

Billolivia yenhoae is unique in the genus in having stolons and up to 52 cm long peduncles. It is most similar to B. citrina in having yellow flowers but differs in having obovate leaves, much longer peduncles, bright yellow corolla lobes, strongly S-curved filaments, and fully hairy ovaries.

Type:— VIETNAM. Khánh Hòa Province: Khánh Vĩnh District, SƠn Thái Commune , approximate coordinates 12°13’01”N and 108°44’50’’E, at 1,061 m elevation, 01 November 2013, Lưu H ồng Trường KH 0941 (holotype SGN!; isotypes SGN!) .

Terrestrial herb to 20 cm tall, stoloniferous; stems to 10 cm, internodes congested; stolons up to 60 cm long, densely pubescent. Leaves alternate; petioles 4‒9 cm long, densely pubescent with brown multicellular uniseriate hairs to 4 mm long; lamina obovate to oblanceolate, slightly asymmetric, 13‒20 cm long, 6‒7 cm wide, base round to cuneate, apex subacute to acute, margin coarsely dentate, 8‒10 of secondary veins on each side of midrib, adaxial lamina dark green, with sparse erect brown hairs to 3 mm long when young, glabrous when mature, margin densely ciliate, abaxial lamina pale green, with dense erect brown hairs to 5 mm long on midrib and venation, glabrous on lamina between veins. Inflorescences axillary, thyrse, to 15-flowered; peduncle light green, 10‒52 cm long, densely pubescent; ray white to light green, to 15 cm long, pubescent; bracts oblong to oblanceolate, light green, to 3.5 × 1 cm, apex acute, abaxially densely pubescent, with ciliate margins; pedicels white, 4‒5.5 cm long, pubescent. Calyx of 5 lobes almost divided to base, white to light green, outside densely brown long pubescent, inside glabrous; lobes narrowly triangular, to 12 mm long, to 2 mm wide at base, apex acute, with ciliate margins. Corolla 28−34 mm long, composed of a narrow tube and a 2-lipped limb with lobes recurved; tube 18‒21 mm long, white, contracted below the middle, then slightly flaring towards mouth, outside pubescent, inside glabrous; throat yellow, glabrous and with purple lines; upper lip 2- lobed, lobes 1.3−1.5 × 9−11 mm, ovate; lower lip 3-lobed, lobes slightly obovate, 12−14 × 8−9 mm; all lobes bright yellow, with purple lines at base, outside sparsely pubescent with multicellular uniseriate hairs to 5 mm, inside with shortly stalked glands. Stamens inserted at the middle of the corolla tube; filaments 6‒7 mm long, strongly S-curved, white, with sparse glandular hairs on upper half. Disc bowl-shaped, obscurely 5-lobed, 1.5 mm high. Ovary 5‒5.5 mm long, 2.5 mm in diameter, fully covered with dense stalked glands; style 13‒14 mm long, densely covered with glandular hairs; stigma 2-lobed, ciliate. Fruits ovoid, around 10 × 0.6 mm, brown hairy, translucent violet and with persistent style.

Additional specimens examined (paratypes): — VIETNAM. Khánh Hòa Province: Khánh Vĩnh District, SƠn Thái Commune, approximate coordinates 12°13’01”N and 108°44’50’’E, at 1,040 m elevation, 12 November 2016, Lưu H ồng Trư ờng, Nguyễn Qu ốc Đạt & Nguyễn Tr ần Qu ốc Trung NF-BOL-KH 036 ( SGN!) ; 26 November 2016, Ph ạm H ữu Nhân & Lưu H ồng Trư ờng PHN12-01 ( SGN!, PHH!, HNU!, VNMN!) .

Distribution, habitat and phenology: — Growing in scattered clumps on moist gulleys in montane moist evergreen closed forest at around 1,060 m elevation, SƠn Thái Commune, Khánh Vĩnh District, Khánh Hòa Province, Vietnam. Flowering was seen in November to January.

Etymology: — The species is named after the first author’s beloved wife LƯƠng Thị Yên Hòa for her invaluable support for his interest in botany.

Vietnamese name: — LƯu hoa Yên Hòa.

Proposed IUCN conservation status: — The species is only known from a single population of less than 250 individuals growing in a less than 1 km 2 watershed of an unnamed stream, which is less than 100 m away from a recently built national road. We have not found any additional populations even though we have been surveying biodiversity in the whole Khánh Hòa Province and neighbouring provinces since 2012. This is a really rare species distributed in a forest where human impacts, including illegal logging, are common. This species, therefore, should be considered for listing in the Critically Endangered category, CR B2a&b(i,ii&iii) ( IUCN 2012).

Notes:— Billolivia yenhoae is the first taxon in the genus known to have vegetative propagation by stolons, which may form colonies in separated gulleys. It grows with an undescribed Billolivia with distinguishably hairy leaves, which will be the subject for another paper. Billolivia yenhoae has the longest peduncles in the genus. Its yellow flowers recall those in B. citrina but B. yenhoae is distinct in having obovate to oblanceolate leaves, much longer peduncles, larger flowers, bright yellow corolla lobes, S-curved filaments, and fully hairy ovaries.

Figures

FIGURE 2. Billolivia yenhoae. A. Habit. B. Leaf, adaxial and abaxial laminas. C. Inflorescence. D. Flowers, front and side views. E. Longisection of corolla showing the gynoecium. F. Stamens. G. Open anthers. H. Stigma. I. Cross section of ovary. Photo: Lưu Hồng Trường.