Research Article |
Corresponding author: Van Son Dang ( dvsonitb@gmail.com ) Academic editor: Yasen Mutafchiev
© 2018 Van Son Dang, Ba Vuong Truong, Thi Phuong Thao Nguyen, Nghia Son Hoang.
This is an open access article distributed under the terms of the CC0 Public Domain Dedication.
Citation:
Dang VS, Truong BV, Nguyen TPT, Hoang NS (2018) Tacca khanhhoaensis V.S. Dang & Vuong (Taccaceae), a new species from southern Vietnam. PhytoKeys 114: 115-122. https://doi.org/10.3897/phytokeys.114.29367
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Tacca khanhhoaensis V.S. Dang & Vuong (Taccaceae) is described as a new species from Hon Ba Nature Reserve in southern Vietnam. This species is morphologically similar to T. chantrieri and T. ampliplacenta but differs from its allies by several salient characters: size of leaves and petioles, inflorescent much shorter leaves, number of flowers, stigma lobes, buds colour. A description, conservation assessment, together with photographs and a key to the species of Tacca in Vietnam are presented.
Hon Ba Nature Reserve, Khanh Hoa, Taccaceae , Taxonomy, Vietnam
The family Taccaceae is composed of only one genus, Tacca J.R. Forster & G. Forster and its 11 species (Ding et al. 2000). Its species are distributed mainly in tropical regions of Asia and Oceania, except for T. parkeri Seem. known only in South America (
During botanical field surveys in Hon Ba Nature Reserve, Khanh Hoa Province, southern Vietnam in 2017, a species of Tacca was collected. After thorough examination of the Tacca species in
The description of the new species was based on material collected in Hon Ba Nature Reserve (over 19,000 ha), Khanh Hoa Province, southern Vietnam (Figure
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.
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.
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!).
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.
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!).
Flowers were observed in April and May. Immature and mature fruits were observed in May and June.
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.
The name of this species is derived from the name of the province Khanh Hoa, where the species was discovered.
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 (
Tacca khanhhoaensis is morphologically similar to T. chantrieri and T. ampliplacenta. The comparisons of morphological characters amongst these three species are summarised in Table
Morphological comparison of Tacca khanhhoaensis with its closest congeners (modified from
Characters | T. khanhhoaensis | T. chantrieri | T. ampliplacenta |
---|---|---|---|
Leaves | |||
– number | 5 to 8 | 3 to 12 | 5 to 10 |
– shape of leaf lamina | oblong to obovate or oblong-elliptic | oblong to oblong-elliptic | oblong-obovate |
– length of leaf lamina | 30–45 cm | 20–50(–60) cm | 55 cm |
– length of petiole | 14–22 × 0.5–1 cm | 11–43 × 0.2–0.5 cm | 30–50 × 0.7–1.2 cm |
Inflorescence | |||
– number of flowers | 5 to 10 | 15 to 25 | 25 |
– length of scape | 20–38 cm | 6–63 cm | 40–70 cm |
– outer involucral bracts | ovate-lanceolate, | ovate-lanceolate, | lanceolate to oblong-ovate, |
4.5–5.5 × 2–2.5 cm | 2–9 × 0.8–4 cm | 6–8 × 3–4 cm | |
– inner involucral bracts | broadly ovate, | broadly ovate, | broad-triangular, |
6–6.5 × 4–5 cm | 2.5–10 × 1.5–9 cm | 10–16 × 8–10 cm | |
Flowers | |||
– colour of buds | dark red | green | black-purple |
– outer perianth lobes | narrowly ovate or triangular, | oblong-ovate or narrowly triangular, | oblong, |
10 × 3–5 mm | 5–12 × 3–8 mm | 12 × 8 mm | |
– inner perianth lobes | broadly ovate, | broadly ovate or triangular, | broad-ovate, |
8–10 × 4–6 mm | 4–11 × 4–12 mm | 12 × 10 mm | |
Apex of stigma lobes | 2-lobed | 3-lobed | 2-lobed |
Ovaries | 5–6 × 8–9 mm | 2–7 × 3–5 mm | 5–8 × 10 mm |
Fruits | 3–4 × 1.5–2 cm | 2–4 × 1–2 cm | 4–6 × 2–2.5 cm |
Seeds | 1.5–5 × 1–1.5 mm, slightly brown, 4–7-ribbed | 2–4 × 1–2 mm, brown, 9–14-ribbed | 2–3 × 1.5–2 mm, brownish-red, many ribbed |
1 | Leaves lobed | 2 |
– | Leaves entire | 3 |
2 | Leaves 3-lobed, each lobe pinnately. Filiform bracts present | T. leontopetaloides |
– | Leaves 3–13-lobed, each lobe simple. Filiform bracts absent | T. palmata |
3 | Leaf-base attenuate and decurrent. Fruit dehiscent | T. plantaginea |
– | Leaf-base attenuate but not decurrent. Fruit indehiscent | 4 |
4 | Inner two involucral bracts long petiolate | T. integrifolia |
– | Inner two involucral bracts sessile | 5 |
5 | Inner involucral bracts suborbicular-fan-shaped | T. subflabellata |
– | Inner involucral bracts broadly ovate | 6 |
6 | Inflorescence with 15–25-flowered. Apex of stigma lobes 3-lobed. Seeds reniform, brown, 9–14-ribbed | T. chantrieri |
– | Inflorescence with 5–10-flowered. Apex of stigma lobes emarginated or 2-lobed. Seeds reniform, slightly brown, 4–7-ribbed | T. khanhhoaensis |
Authors are grateful to the staff of the Hon Ba Nature Reserve for their kind assistance during the field survey. We thank the curators and staff of the herbaria at the VNM, HN and VNMN for their help in accessing specimens. This work was partly supported by the National Collection Project (BSTMV.20/16-21) of the Vietnam Academy of Science and Technology, Vietnam.