Trivalvaria rubra 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 rubra Y.H.Tan, S.S.Zhou & B.Yang sp. nov. Figure 1

Diagnosis.

Trivalvaria rubra is similar to Trivalvaria costata in flower size and petal shape and size and also shares similarities with T. macrophylla in leaf shape, but can be distinguished by its pink flowers, androdioecious, petals spreading, outer petal lanceolate to narrowly oblong, 14-20 × 4-6 mm, inner petal 17-25 × 4-7 mm, oblong-ovate to ovate-triangular.

Type.

MYANMAR. Kachin State, Putao District, on the way from Nanmti to Nahsihbo, 27°24'29"N, 97°39'59"E, 890 m a.s.l, 16 May 2017, Myanmar Exped. 1801 (holotype, HITBC!; isotype, RAF!).

Description.

Shrubs up to 1.2 m high. Young twigs densely to very sparsely pubescent, older twigs glabrous to pubescent. Leaves subcoriaceous, glabrous above, sparsely pubescent beneath, obovate to narrowly elliptic or oblong-lanceolate, 13.5-27.5 × 4.2-10.5 cm, base cuneate to obtuse, apex attenuate to acuminate or acute, sometimes retuse, midrib sunken above, prominent beneath, sparsely pubescent, lateral veins 9-11 pairs, faintly distinct above, prominent beneath, smaller veins faintly prominent beneath. Petiole 5-10 mm long, 2-3 mm thick, pubescent to glabrous. Flowers pink, androdioecious 2.6-2.8 cm in diam., extra-axillary or ramiflorous, solitary or sometimes in pairs, Bracts 2-4 (Fig. 1 .G1), triangular to ovate, 3-6 × 2.5-5 mm, pubescent outside. Pedicel 2-3 mm long, pubescent. Sepals 3 per flower (Fig. 1 .G2), free or sometimes shortly connate, triangular to triangular-ovate, 6-9 × 3-6 mm, pubescent to densely pubescent outside, glabrous inside, base rounded, apex acute to acuminate. Petals 6 per flower in two whorls, sub-equal, imbricate, spreading, outer petals (Fig. 1 .G3) lanceolate, or oblong-ovate to ovate-triangular, 14-20 × 4-7 mm, pubescent to sparsely pubescent outside, glabrous inside, base rounded to obtuse, apex acute to acuminate; inner petals (Fig. 1 .G4) lanceolate or narrowly oblong, 17-25 × 4-6 mm, sparsely pubescent outside, glabrous inside, base rounded to obtuse, apex acute to acuminate. Stamens numerous, ca. 2 mm long, apex shield-like, sometimes tongue-shaped in outer whorl, glabrous; torus triangular conical. Carpels several or many, 15-25 per flower, ovary densely hairy, stigma more or less subglobose, pubescent. Fruiting pedicel 3-4 mm long. Monocarps green, pink to red, ca. 5-10 per fruit, ellipsoid or oblong, 15-18 × 7-10 mm, sparsely pubescent, stipe 2-5 mm, pericarp thin. Seed one per monocarp.

Phenology.

Flowering in May to June and fruiting occurs from June to December.

Etymology.

The species epithet refers to its pink flower.

Distribution and habitat.

Trivalvaria rubra is hitherto known from the type locality of Putao, Kachin state in Northern Myanmar, it is a small shrub that grows in the understory in tropical dipterocarpa forests, the dominant tree species are Shorea assamica , Dysoxylum mollissimum , Aglaia elaeagnoidea , Garcinia spp., Goniothalamus peduncularis , Antidesma spp., shrub species are Hymenandra wallichii , Ardisia sp., Zingiber sp., at an elevation of ca. 600-900 m a.s.l.

Conservation status.

Trivalvaria rubra was collected on the way from Namti to Nahsihbo, Putao, Northern Myanmar, this area being difficult to travel due to its rugged terrain. At least three populations and ca. 60 individuals per population have been discovered. 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, near Nahsihbo village, 27°24'36"N, 97°36'26"E, 970 m a.s.l, 11 Dec. 2017, Myanmar Exped. 3373 (HITBC!); Putao District, near Namti village, 27°24'43"N, 97°39'56"E, 820 m a.s.l, 15 Dec. 2017, Myanmar Exped. 3698 (HITBC!).

Figures

Figure 1. Trivalvaria rubra Y. H. Tan, S. S. Zhou & B. Yang, sp. nov. A Habitat B Branch with flowers (adaxial view) C Branch with flowers (abaxial view) D Male flower (abaxial view) E Flower bud (side view) F Female flower (abaxial view) G Flower (G 1 Bracts; G 2 Sepals; G 3 Outer petals; G 4 Inner petals; G 5 Androphore) H Fruit. Photographed by Y. H. Tan, H. B. Ding and B. Yang.