Polyalthia pumila Ridl. J. Straits Branch Roy.Asiat. Soc.

Bunchalee, Pasakorn, Leeratiwong, Charan & Johnson, David M., 2021, Two new species and a new record of the genus Polyalthia (Annonaceae) from Peninsular Thailand, Phytotaxa 510 (3), pp. 239-250 : 246-248

Polyalthia pumila Ridl. J. Straits Branch Roy.Asiat. Soc. 54: 12. (1910).

TYPE: Peninsular Malaysia, Perak, Dindings, Sera Woods , March 1896, Ridley 7996 (lectotype SING [ SING0059298 ], designated by Turner, Gard. Bull. Singapore 64: 241. 2012 ; isolectotype K! [ K000691442 ] ). ( Figs. 5 & 6 )

Shrubs 0.8‒1.2 m tall, bark smooth, blackish brown, primary branching spiral. Young branches rusty brown to dark brown tomentose, the hairs erect and ca. 1.0 mm long, with moderately prominent lenticels. Leaves with petioles stout, 3.0‒6.0 mm long, flat above, rusty‒brown tomentose; lamina coriaceous, smooth, symmetrically or asymmetrically elliptic, oblanceolate or obovate, (12.0‒)15.0‒30.0 × (4.5‒)6.0‒11.0 cm, base asymmetrically cordate with auricles 2.0‒ 3.0 mm long, apex acute to acuminate with acumen 7.0‒15.0 mm long, upper side glabrous except on base of midrib, which is sparsely puberulous, lower side glabrescent, puberulous along midrib; midrib grooved above; lateral veins (10‒)12‒16 per side, fairly straight, diverging at 55‒65° from the midrib, simple loop-forming 3.0‒4.0 mm from the margins; intersecondary veins present; tertiary veins reticulate. Inflorescences supra-axillary on leafy branches, 1(‒3)- flowered; pedicels 1.5‒3.5 mm long, 1.5‒1.8 mm thick, pubescent; bract solitary, linear, 1.5‒2.5 × ca. 0.8 mm, attached at pedicel base, sparsely pubescent outside and glabrous inside; bud lanceolate, petals separate at base, valvate at apex. Sepals imbricate, brownish-green in vivo, ovate, 5.0‒6.0 × 4.0‒5.0 mm, apex acute, sparsely pubescent outside and glabrous inside. Petals orangish red to red, coriaceous, separate, erect, apex acute; outer petals lanceolate, 23.0−30.0 × 3.0−5.0 mm; inner petals linear, 25.0‒33.0 × 2.0‒3.0 mm. Stamens orangish red to red, slightly cuneate, 1.3‒1.5 × 0.6‒0.7 mm, filament ca. 0.2 mm long, anthers ca. 1.0 mm long; anther connective apex truncate; androecium 5.0‒6.0 mm in diameter. Carpels 10‒15 per flower, 2.2‒2.5 × 0.3−0.4 mm, pubescent, style rudimentary, stigmas clavate, 1.0‒ 1.2 mm, pubescent, exceeding the height of the anther connective apices; ovules ca. 2 per carpel, attached laterally. Torus cushion-shaped and slightly concave at top, 2.5‒3.0 mm in diameter, 1.0‒ 1.2 mm thick, glabrous. Fruits with 7‒12 monocarps on pedicels 18.0‒25.0 mm long, 1.8−2.0 mm thick, pubescent. Monocarps greenish yellow when ripe, globose to subglobose or suboblongoid, 9.0‒12.0 × 8.0‒9.0 mm, base rounded, apex mucronate, glabrous, stipes 1.0‒2.0 mm long, 1.0‒ 1.2 mm thick. Seeds plano-convex, 1‒2 per monocarp, ca. 8.0 × 7.0 × 4.0 mm, grooved in horizontal view, surface rugulate and sparsely pitted, slightly shiny.

Distribution and Ecology: —Understory of tropical rain forest in Narathiwat Province near the southern border of Peninsular Thailand ( Fig. 7 ), south to Perak and Johor States of Malaysia ( Ridley 1910).

Phenology: —Flowering and fruiting in April.

Local name: —Thai: Saed sri nara.

IUCN Conservation status: —The plant is known from single locality in Thailand. In Peninsular Malaysia it was reported from two widely separated localities in the original description but it has not been re-collected since 1896. Therefore, this species is considered as Data Deficient (DD).

Specimen examined: — THAILAND. PENINSULAR: Narathiwat, Cha Nae District, Dusong Yo Subdistrict, Ruepoh village , Mo Tae Mountain , 4 April 2020 (flower & fruit), Leeratiwong 20-1528 (PSU) .

Notes: —This is the first report of Polyalthia pumila for Thailand. The species is notable for its stature, among the shortest in the family ( Sinclair 1955). It is similar to P. motleyana and its relatives in having branches with distichous phyllotaxis, a lamina with a more or less bullate surface, the leaf base more or less cordate, and secondary veins with simple brochidodromous venation.

Figures

FIGURE 5. Polyalthia pumila: A. Habit; B. Inflorescence, showing supra-axillary attachment; C. Base of flower, with petals removed to show stamens and carpels; D. Sepals (outside below, inside above); E. Outside of outer petal; F. Outside of inner petal; G. Stamens (inside view on left, outside view on right); H. Carpel; I. Fruit; J. Monocarp. The illustration was drawn by Thadanai Saensuk from Leeratiwong 20-1528 (PSU).

FIGURE 6. Polyalthia pumila: A. Twig and flowers; B. Flowers and a single monocarp; C. Upper surface of leaf base; D. Lower surface of leaf; E. Fruit; F. Seed (Side view). Photographs in A & B were taken Charan Leeratiwong in Narathiwat, Cha Nae District, Dusong Yo Subdistrict, Ruepoh village, Mo Tae Mountain, 4 April 2020. C, D, E & F are from Leeratiwong 20-1528 (PSU); photographs by Pasakorn Bunchalee.

FIGURE 7. A. & B. Maps showing distributions of Polyalthia heliopetala (●), P. taweensis (▲) and P. pumila (■) in southern Peninsular Thailand. Map in B is an enlargement of the area shown in the rectangle in A. Maps by Pasakorn Bunchalee.