Goniothalamus flagellistylus Tagane & V. S. Dang

Tagane, Shuichiro, Dang, Van Son, Yahara, Tetsukazu, Toyama, Hironori & Tran, Hop, 2015, Goniothalamus flagellistylus Tagane & V. S. Dang (Annonaceae), a new species from Mt. Hon Ba, Vietnam, PhytoKeys 50, pp. 1-8: 3-4

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scientific name

Goniothalamus flagellistylus Tagane & V. S. Dang

sp. nov.

Goniothalamus flagellistylus Tagane & V. S. Dang   sp. nov. Figs 1 View Figure 1 , 2 View Figure 2


Similar to Goniothalamus tortilipetalus   M.R.Hend., but differing from that species in having 308-336 stamens (vs. ca. 170-260) and ca.120 carpels (vs. ca. 50-100) per flower, and stigmas and pseudostyles ca.8.5 mm (vs. 4-4.5 mm) long.


Vietnam, Khanh Hoa Province, Hon Ba Nature Reserve, in evergreen forest near stream, 12°06.51'N, 108°59.23'E, alt. 400 m, Tagane S., Kanemitsu H., Dang V.S., Tran H. with Hanh N., Loi X.N., Thach N.D., Dinh N., Hieu P.N.H. V1497, 12 July 2014, Fl., holotype: KYO!; isotypes: BKF!, FU!, K!, VNM!, the herbarium of Hon Ba Nature Reserve!).


Small trees, 11 m tall, DBH 8 cm. Young twigs sparsely covered with brown hairs, soon glabrous, blackish when dry. Petioles 1-1.2(-1.5) cm long, 2.5-3.5 mm in diam., glabrous, black when dry. Leaf blades narrowly oblong-elliptic, 31-45 × 8.2-11.5 cm, length/width ratio 2.7-4.0, 185-225 µm thick, base acute to obtuse, margin entire, revolute when dry, apex acuminate, acumen ca. 1.5 cm long, leathery, slightly shiny above, glabrous on both surfaces; midribs impressed above, prominent below, glabrous on both surfaces, secondary veins 16-20 pairs, arising at an angle of 60-70 degrees from a midrib, prominent on both surface when dry, glabrous on both surfaces, tertiary veins distinct above, slightly distinct below. Flowers solitary, arising from main trunks and older branches, pendent; pedicels 19-25 mm long, 1.5-2.5 mm in diam., glabrous; bracts 3-4, very broadly triangular to hemiorbicular, ca. 1.6 mm long, brownish pubescent outside, glabrous inside, margin sometimes ciliate. Sepals ovate-triangular, 2.2-2.8 × 2.2-2.8 cm in flower, accrescent, increasing to 3.3 × 3.8 cm in fruit, 200-210 µm thick, basally connate, greenish in vivo, glabrous outside, sparsely covered with brown hairs inside, veins reticulated, distinct outside, indistinct inside. Outer petals oblong-ovate to narrowly ovate, 6-9. 2 × 2.2-3.1 cm, length/width ratio 2.7-3.4, 380-450 µm thick, greenish, glabrescent outside, sparsely covered with short brown hairs inside, except at base velutinous, veins faintly visible outside, indistinct inside. Inner petals rhombic, 1.6 × 0.7 cm, length/width ratio ca. 1.9, 1100-2100 µm thick, greenish, pubescent outside, velutinous inside with 12-14 basal grooves. Stamens 308-336 per flower, flattened-oblong, 3.8-4.8 × 0.6 mm, glabrous; connectives long-apiculate, 1.2-1.5 mm long, apiculate length 0.5-0.9 mm long, densely covered with cream-white hairs. Carpels ca. 120 per flower; ovary 1.4-1.7 × ca. 0.3 mm, densely covered with golden-brown hairs; stigmas and pseudostyles flagellate, ca.8.5 mm long, L-shaped curved in the middle, yellowish in vivo, blackish when dry, glabrous, tip awl-shaped. Fruits with persistent calyx, fruiting pedicels 2.7 cm long, 3-4.5 mm in diam. Monocarps 22, ellipsoid, 1.6-1.7 cm long, ca. 1.0 cm in diam., base attenuate, apex apiculate, glabrous, reddish-brown, pericarp ca. 0.5 mm thick when dry; stipes 0.6-1.2 mm long, ca. 2 mm in diam., glabrous. Seeds one per monocarp, 1.5 cm long, 0.8-1.0 cm in diam., yellowish brown, glabrous, seeds with copious surrounding mucilage.


Mature flowers and fruits were collected in July and November, respectively.

Distribution and habitat.

This species is known only from Mt. Hon Ba, Khanh Hoa Province, South Vietnam. The small population was found on a slope in broad-leaved evergreen forest, ca. 100 m apart from a rapid river, where Ixonanthes reticulata   Jack, Palaquium   sp., Gironniera subaequalis   Planch., Archidendron chevalieri   (Kosterm.) I.C.Nielsen, Barringtonia augusta   Kurz, Barringtonia macrostachya   (Jack) Kurz, Camellia krempfii   (Gagn.) Sealy, Streblus indicus   (Bureau) Corner, Xerospermum noronhianum   Blume and Pandanus fibrosus   Gagnep. are dominated.

Other specimen examined.

Vietnam, Khanh Hoa Province, Hon Ba Nature Reserve, in evergreen forest near stream, 12°06.51'N, 108°59.23'E, alt. 400 m, Toyama H., Tagane S., Dang V.S., Nagamasu H., Naiki A., Tran H., Yang C.J. with Cuong N.Q., Hieu H.N.P. V1972, 22 November 2014, Fr. (FU!, KYO!, NTU!, VNM!, the herbarium of Hon Ba Nature Reserve!).


The specific epithet is in reference to its flexuous styles which is too long to insert straight in the pollination chamber that formed by the inner petals.

GeneBank accession No.

Tagane et al. V1497: LC010815 (rbcL), LC010816 (matK).

Similar species.

Goniothalamus flagellistylus   is morphologically similar to Goniothalamus calvicarpus   Craib, Goniothalamus griffithii   Hook.f. & Thomson, and Goniothalamus tortilipetalus   , all of which form a monophyletic group ( Nakkuntod et al. 2009) and are characterized by relatively large sepals with distinct veins and stamens with long apiculate connectives ( Saunders and Chalermglin 2008). Among the three species, Goniothalamus flagellistylus   is most similar to Goniothalamus tortilipetalus   , which is distributed in the Malay Peninsula, in having more than 200 stamens and more than 50 carpels. In fact, The BLAST similarity search based on the matK sequence of Goniothalamus flagellistylus   resulted in homology as high as 734/736 bp with the sequence of Goniothalamus tortilipetalus   (GeneBank accession no. EU715081) in the DNA database. However, as described in the diagnosis above, the two species can be easily distinguished by the number of stamens and carpels per flower, and style length (Table 1). Also, Goniothalamus flagellistylus   is different from Goniothalamus tortilipetalus   in that flowers arise not only from the main trunk but also from the older branches as in Goniothalamus calvicarpus   and Goniothalamus griffithii   ( Saunders and Chalermglin 2008).

Conservation status.

Data deficient. Goniothalamus flagellistylus   is known from a single population, including only six individuals: only one produces flowers/fruits while the others are just saplings. This situation satisfies the CR (critically endangered) status in criterion D of IUCN Red List Categories ( IUCN 2014). However, more individuals could be found if neighboring areas are more thoroughly surveyed. Thus, we regard the conservation status as DD. In Mt. Hon Ba, large areas of primary evergreen forest below 300-400 m elevation had been cleared or selectively logged before the Hon Ba Nature Reserve established, and it is likely that some habitats of this species were lost. The forest habitat where we found Goniothalamus flagellistylus   remains less disturbed under a lower level of logging activities probably because of its landform of the steep slope near the rapid river. The forest in this Nature Reserve is currently protected well from anthropogenic activities, and recovering better and better. The current data available are not enough for a risk evaluation, we therefore need special attention to the individuals/populations of Goniothalamus flagellistylus   and its distribution.