Tacca khanhhoaensis V.S. Dang & Vuong, 2018

Dang, Van Son, Truong, Ba Vuong, Nguyen, Thi Phuong Thao & Nghia Son Hoang,, 2018, Tacca khanhhoaensis V. S. Dang & Vuong (Taccaceae), a new species from southern Vietnam, PhytoKeys 114, pp. 115-122 : 115

Tacca khanhhoaensis V.S. Dang & Vuong sp. nov. Figures 2 , 3

Diagnosis.

Tacca khanhhoaensis is similar to Tacca chantrieri André in leaf shape and bracts, but differs from it in having shorter leaves (up to 45 cm vs. 60 cm long) and petioles (up to 22 cm vs. 43 cm long), inflorescences with fewer flowers (5 to 10 vs. 15 to 25), 2-lobed stigma vs. 3-lobed stigma and dark red buds vs. green buds. The new species is also somewhat similar to T. ampliplacenta L. Zhang & Q.-J. Li of China, but differs from it by having smaller leaves (30-45 × 10-14 cm vs. 55 cm long) and fruits (3-4 × 1.5-2 cm vs. 4-6 × 2-2.5 cm) and very short petioles (22 cm vs. 50 cm long), inflorescent much shorter leaves (vs. longer), number of flowers (5 to 10 vs. 25) and dark red buds vs. black-purple.

Type.

VIETNAM. Khanh Hoa Province, Hon Ba Nature Reserve, terrestrial under the shade of the canopy on dry soil or close to the stream, alt. 353 m, 12°06.36'N, 108°59.46'E, 16 April 2017, Truong Ba Vuong, Mang Van Lam, Dang Van Son, BV256 (holotype VNM!; isotype VNM!, the herbarium of Hon Ba Nature Reserve!).

Description.

Perennial herbs. Rhizome cylindric, fleshy, with many stout roots. Leaves radical, 5 to 8 leaves; laminae oblong to obovate or oblong-elliptic, 30-45 × 10-14 cm, apex acute, base attenuate, margin slightly undulate; main veins pinnate; petiole erect, 14-22 × 0.5-1 cm, green to purplish-green, sheathing at base. Inflorescence umbel, 5-10-flowered; scape erect, 20-38 cm long, nodding, pale green-purple at base, more dark purple above. Involucral bracts 4, decussate, sessile; two outer bracts vertical arrangement, unequally, ovate-lanceolate, 4.5-5.5 × 2-2.5 cm, black-purple, apex acuminate, base obtuse; two inner bracts horizontal arrangement, broadly ovate, 6-6.5 × 4-5 cm, deep purple red with dark purple at margin, apex acuminate, base rounded, margin undulate, slightly erose at base, possessing numerous veins. Filiform bracts 8-15, up to 32 cm long, dark purple. Flowers narrowly triangular, buds dark red flowers greenish-purple when young, when older black-purple; perianth tube 5-6 mm long, white and purple inside. Perianth lobes 6, three outer lobes narrowly ovate or triangular, 10 × 3-5 mm, apex acute; three inner lobes broadly ovate to ovate-triangular, 8-10 × 4-6 mm, apex acuminate, recurved when flower fully opening. Stamens 6, attached to the base of perianth tube, beset with stigma lobes, dark purple to dark red, filament short, anther and connective forming a hood-like structure, individual stamens with 2 thecae, each theca 2 mm long. Stigma 3, ca. 5 mm in diameter, fleshy, apex 2-lobed with finely white pubescence, lobes slightly curved down; style 8-9 mm in diameter, sub-orbicular to round-triangular in outline, surface with minute black hairs. Ovaries inferior, obtriangular, 5-6 × 8-9 mm, dark red. Fruit berry, 3-4 × 1.5-2 cm, black to dark purple, triangular in transverse section; stalk 1.5-2 cm long. Seeds reniform to nearly half orbicular, 1.5-5 × 1-1.5 mm, slightly brown, 4-7-ribbed.

Other specimen examined.

VIETNAM. Khanh Hoa Province, Hon Ba Nature Reserve, growing under forest canopy, uncommonly along the riparian forest, alt. 400 m, 12°06.37'N, 108°59.44'E, 16 November 2017, Truong Ba Vuong, Mang Van Lam, BV256a (VNM!, the herbarium of Hon Ba Nature Reserve!).

Phenology.

Flowers were observed in April and May. Immature and mature fruits were observed in May and June.

Distribution and habitat.

Tacca khanhhoaensis is only known from Hon Ba Nature Reserve, Khanh Hoa Province, southern Vietnam. It was growing under the shade of the canopy on dry soil or close to the stream, where Aporosa tetragona Tagane & V.S. Dang, Bambusa sp., Barringtonia macrostachya (Jack) Kurz, Calamus sp., Croton sp., Desmos sp., Goniothalamus flagellistylus Tagane & V.S. Dang, Ixora sp., Microcos tomentosa Sm., Phyllanthus reticulatus Poir. and Streblus indicus (Bureau) Corner are dominant.

Etymology.

The name of this species is derived from the name of the province Khanh Hoa, where the species was discovered.

Conservation status.

Tacca khanhhoaensis was collected from a small population under forest canopy in Hon Ba Nature Reserve at 300-400 m altitude. The forest habitat where we found this new species was frequently logged and disturbed. Therefore, Tacca khanhhoaensis is assessed as Critically Endangered (CR) based on the IUCN Red List Categories ( IUCN 2012), although some individuals might be found by more thorough surveys.

Note.

Tacca khanhhoaensis is morphologically similar to T. chantrieri and T. ampliplacenta . The comparisons of morphological characters amongst these three species are summarised in Table 1 .

Figures

Figure 2. Tacca khanhhoaensis V. S. Dang & Vuong. A Habit B Inflorescent much shorter leaves C Habitat.

Figure 3. Tacca khanhhoaensis V. S. Dang & Vuong. A Inflorescence B Fruits C Flowers, top view showing perianth lobes, stamens and stigma D Outer perianth lobes E Inner perianth lobes F Inner surface of perianth tube G Anther and connective H Longitudinal section of Anther with a pair of theca I Outer involucral bracts J Inner involucral bracts K Stigmas L Finely pubescent hairs at apex of stigma lobes M Black hairs on style N Longitudinal section of flower O Transverse section of fruit P Transverse section of ovary Q Seeds.