Trivalvaria casseabriae Y.H.Tan, S.S.Zhou & B.Yang, 2018

Yang, Bin, Zhou, Shi-Shun, Ding, Hong-Bo, Li, Ren, Maung, Kyaw Win & Tan, Yun-Hong, 2018, Two new species of Trivalvaria (Annonaceae) from northern Myanmar, PhytoKeys 94, pp. 3-12 : 3

Trivalvaria casseabriae Y.H.Tan, S.S.Zhou & B.Yang sp. nov. Figure 2

Diagnosis.

Trivalvaria casseabriae is similar to Trivalvaria argentea in leaf shape, but can be distinguished by its larger flower size and outer petals equal to inner petals, petals 6-10 × 3-5 mm (vs. 2 × 3 mm), 2-2.5 times as long as wide and elliptic to ovate-elliptic.

Type.

MYANMAR. Kachin State, Putao District, Wasadam to Upper Shankhaung, 27°26'42"N, 97°14'27"E, 850m a.s.l, 21 May 2017, Myanmar Exped. 2379 (holotype, HITBC!; isotype, RAF!).

Description.

Shrubs up to 1.5 m high. Young twigs pubescent, older twigs glabrous to sparsely pubescent. Leaves subcoriaceous, glabrous above, sparsely pubescent beneath, lanceolate to oblong, 12.5-24.5 × 2.5-5.5 cm, base cuneate to obtuse, apex acuminate to caudate, midrib immersed above, prominent beneath, sparsely pubescent, lateral veins 5-7 pairs, immersed and faintly distinct above, prominent beneath, smaller veins faintly prominent beneath. Petiole 3-8 mm long, 1-3 mm in diameter, pubescent. Flowers white, androdioecious, 14-20 mm in diam., solitary or in pairs between leaf axils (extra-axillary), rarely ramiflorous. Bracts 1-2, triangular to ovate-triangular, 2-3 × 1-2 mm, pubescent to densely pubescent outside. Pedicel 2-3 mm long, pubescent. Sepals 3 per flower, free or sometimes shortly connate, ovate to broadly ovate, 2-3.5 × 2-3 mm, pubescent outside, puberulous inside and apex acute to obtuse, base rounded. Petals 6 per flower in two whorls, imbricate, spreading, subequal, outer petals (Fig. 2 .F1) elliptic to ovate-elliptic, 6-10 × 4-5 mm, sparsely pubescent outside, puberulous inside, base rounded to obtuse, apex acute to obtuse; inner petals (Fig. 2 .F2) elliptic to ovate-elliptic, 6-10 × 3-5 mm, sparsely pubescent outside, puberulous inside, base rounded to obtuse, apex acute. Stamens numerous stamens, ca. 2 mm long, apex shield-like, sometimes tongue-shaped in outer whorl, glabrous; torus triangular conical. Carpels 6-10 per flower, with globose stigma, pubescent. Monocarps and seeds not seen.

Phenology.

Flowering at May to July.

Etymology.

The specific epithet is derived from the abbreviation of Southeast Asia Biodiversity Research Institute, Chinese Academy of Sciences (CAS-SEABRI); noun in apposition. The name is dedicated to its three-part mission, viz., (a) Serve China’s "the Silk Road Economic Belt and the 21st Century Maritime Silk Road" initiative; (b) Integrate efforts by CAS and international institutes to organise professional research groups and train researchers in Southeast Asian countries; and (c) Provide support to all domestic and international partners.

Distribution and habitat.

Trivalvaria casseabriae is only known from the type locality of Putao, Kachin state in Northern Myanmar, where it grows in the understory of tropical montane broadleaf forests, the dominant tree species being Altingia excels , Dysoxylum spp., Garcinia spp., Elaeocarpus spp., at an elevation of ca. 700-900 m.

Conservation status.

Although Trivalvaria casseabriae was collected on the way from Wasadam to Upper Shanhkaung, Putao District, Northern Myanmar, only one population and less than 50 individuals, has been discovered. Potential populations and more individuals may be found in future field surveys. Currently, the locality is not legally protected and, although young individuals were recorded in field, the fragmented habitat and continuous logging severely threaten its survival. At present, it is suggested that it be considered as ‘Vulnerable’ (VU) on the basis of current IUCN Red List Categories and Criteria (IUCN, 2012).

Specimen examined

(paratypes). MYANMAR. Kachin State, Putao District, on the way from Wasadam to Upper Shankhaung, 27°26'39"N, 97°14'23"E, 800 m a.s.l, 21 May 2017, Myanmar Exped. 2389 (HITBC!), Putao District, Upper Shanhkaung, 27°26'30"N, 97°14'26"E, 680 m a.s.l, 28 April 2016, Myanmar Exped. 201614 (HITBC!).

Key to the species of the genus Trivalvaria

Figures

Figure 2. Trivalvaria casseabriae Y. H. Tan, S. S. Zhou & B. Yang, sp. nov. A Habitat B Branch C Flower buds (side view) D Flower (adaxial view) E Flower (abaxial view) F Flower (F 1 Outer petals; F 2 Inner petals; F 3 Androphore). Photographed by Y. H. Tan, H. B. Ding and B. Yang.