Trivalvaria ochroleuca Chaowasku & D. M. Johnson 2021, sp. nov.
Creators: name: Johnson, David M.
name: Chaowasku, Tanawat
name: Murray, Nancy A.
name: Chalermglin, Piya
Publisher: name: Zenodo
Year: 2021
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Magnoliopsida
Magnoliales
Annonaceae
Trivalvaria
Trivalvaria ochroleuca

description: Trivalvaria ochroleuca Chaowasku & D.M.Johnson, sp. nov. (Figs. 1A,B, 2B)   
 Type:— THAILAND. Kanchanaburi: Southwestern District, Khao Yai, E of Sangkhla, elev. c. 1100 m, 29 March 1968 (flower), van Beusekom & Phengklai 193 (holotype: BKF-4190!; isotypes: L.2066282! P-00268392!).   
 This new species is distinguishable from T. costata by rounded (versus angular and acute) inner petal apices, greater number of stamens (ca. 180 versus 30–50), and blunt leaf acumen 3–8 mm long (versus acute and up to 26 mm long) (Table 1).   
 Shrubs up to 3 m. Twigs densely but finely brown-tomentose, eventually glabrate. Leaves elliptic to oblanceolate, 15.7–18.2  5.9–6.0 cm, base cuneate to nearly rounded, apex blunt-acuminate, the acumen 3–8 mm long, glabrous except for short coarse hairs along midrib above, with short coarse hairs along midrib and secondary veins but otherwise glabrous below, secondary veins eucamptodromous, 8–9 per side, relatively straight but strongly ascending; petiole 7– 8 mm long. Inflorescences sub-opposite to leaves, 1–2-flowered, peduncles 1.5–3.0 mm long, pedicels ca. 5 mm long, bearing 2 bracts ca. 2 mm long; buds not seen. Flowers bisexual. Sepals triangular, 2.5–3.0 mm long, obtuse, sericeous. Petals spreading at anthesis, white to dirty pale yellow, elliptic-oblong, ca. 5.5  3.5 mm, rounded, glabrous on inner surface, sericeous on outer surface. Stamens ca. 180, forming a globose boss ca. 5.5 mm in diameter, oblong, ca. 1.3 mm long, anther connective apex truncate, glabrous. Carpels ca. 14, ovaries ca. 1.0 mm long, pubescent, stigmas globose, ca. 0.3 mm long, glabrous. Receptacle short-cylindrical, ca. 2.5 mm high, ca. 2.0 mm in diameter, glabrous. Fruit unknown (but see below and Fig. 2E).   
 Distribution and Ecology: —Southwestern Thailand, in dry evergreen forest at 1100–1200 m.   
 Phenology:— Flowering January and March.   
 Etymology:— Named for the flower colours, dull yellow and creamy white.   
 Vernacular name:— Ma khao khao (มะขาวเขา) (Kanchanaburi).   
 Conservation status:— Trivalvaria ochroleuca is known from a single locality, where it has been collected twice, 42 years apart, most recently in 1968. Nothing is known of its relative abundance, or whether it is still present. According to the Kerr itinerary given by Jacobs (1962), this locality is 20 km east of Wangka in northern Kanchanaburi Province. A more recent collection from Tak Province (see below) has been lost. In light of its narrow distribution, T. ochroleuca is given a preliminary conservation assessment of critically endangered.   
 Additional specimen examined:— THAILAND. Kanchanaburi: Kao Ri Yai, ca. 1200 m, 31 January 1926 (flower), Kerr 10368 (BK, L.4311236).   
 Notes:— An additional specimen from nearby Tak Province in Thailand was unfortunately lost, but the flower was photographed (Fig. 2B). A DNA sequence was obtained for phylogenetic analysis (Chaowasku, unpubl.). Similarly, the fruit (Fig. 2E) of a Trivalvaria plant photographed in Prachuap Khiri Khan Province is probably this species. A specimen collected by Gallatly from a slightly higher elevation in southern Myanmar (Molyet, 5000 ft., 19 Jan 1877, K), cited by King (1892: 27), under Ellipeia costata King, may also represent this species.
description: Published as part of Johnson, David M., Chaowasku, Tanawat, Murray, Nancy A. & Chalermglin, Piya, 2021, Three new species of Trivalvaria (Annonaceae) from Thailand, with a key to the Thai species, pp. 79-86 in Phytotaxa 489 (1) on page 80, DOI: 10.11646/phytotaxa.489.1.6, http://zenodo.org/record/5757631