Polyalthia heliopetala Leerat. & Bunchalee, 2021

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 : 240

Polyalthia heliopetala Leerat. & Bunchalee , sp. nov. ( Figs. 1 & 2 )

Polyalthia heliopetala resembles P. oblonga King (1892: 65) and P. motleyana (Hook.f.) Airy Shaw (1939: 280) but differs from P. oblonga in the flower pedicels 7.0‒10.0 versus 31.0‒57.0 mm long and lanceolate versus oblong inner petals and from P. motleyana in the oblong to lanceolate rather than ovate petals and the monocarp stipes 18.0‒25.0 versus ca. 10.0 mm long. It differs from both species in having embossed patches on the inner bases of the petals.

Type:— THAILAND. Narathiwat, Ra Ngae District, Bo Ngo Subdistrict , Bue Chaeng Village , 7 April 2020 (flower & fruit), Leeratiwong 20-1527 (holotype PSU! ; isotype BKF! ).

Shrubs 2.0‒4.0 m tall, bark smooth, greyish black, primary branching spiral. Young branches rusty-brown tomentose, the hairs erect, 0.7‒1.0 mm long, with moderately prominent lenticels. Leaves with petioles stout, 2.0‒3.0 mm long, 3.0‒ 3.5 mm thick, flat above, rusty‒brown tomentose; lamina chartaceous, asymmetrically elliptic to oblanceolate and slightly curved inward, 18.0‒32.0 × 5.0‒10.0 cm, base asymmetrically cordate with auricles 1.0‒2.0 mm long, apex cuspidate to acuminate with an acumen 8.0‒10.0 (‒12.0) mm long, upper side glabrous except for the sparsely tomentose midrib, lower side glabrous except for hairs along midrib and lateral veins; midrib grooved above; lateral veins 14‒16 per side, slightly arched towards the apex, at midpoint diverging at 60‒70° from the midrib, festooned loop-forming 1.5‒2.0 mm from the margins; intersecondary veins present; tertiary veins weakly scalariform. Inflorescences 1(‒3)- flowered, supra-axillary or terminal on leafy branches; pedicels 7.0‒10.0 mm long, 1.5−2.0 mm thick, puberulous; bracts 2, attached at the pedicel base, lanceolate, 1.8‒2.0 × 1.0‒ 1.2 mm, apex acute, puberulous outside and glabrous inside. Sepals valvate, brownish yellow in vivo, ovate, 5.0‒6.0 × 3.0‒4.0 mm, apex acuminate with acumen ca. 1.0 mm long, puberulous outside and glabrous inside. Petals yellow, orange, or brownish orange in vivo, coriaceous, erect or slightly recurved, apex acute, inner surface embossed with a shallowly ovate basal patch (most visible in fresh condition), pubescent outside, glabrous inside; outer petals oblong or lanceolate, 15.0−18.0 × 5.0−7.0 mm; inner petals lanceolate, 17.0‒22.0 × 3.0‒5.0 mm. Stamens yellow in vivo, slightly cuneate, 2.0‒2.2 × 0.5‒0.6 mm, filament ca. 0.3 mm long; anthers 1.6‒1.8 mm long, anther connective apex truncate; androecium 7.0‒9.0 mm in diameter. Carpels 12‒15 per flower, 2.6‒2.8 × 0.5−0.6 mm, pubescent, style rudimentary, stigmas obovoid or oblong, 0.5‒0.7 mm, pubescent, equal in height to the anther connective apices; ovules 2 per carpel, attached laterally. Torus convex, slightly concave at the apex, 3.0‒4.0 mm in diameter, 1.8‒2.0 mm thick, glabrous. Fruits with 22‒28 monocarps on pedicels 10.0‒15.0 mm long, 1.5−1.8 mm thick, glabrous. Monocarps green in vivo (immature), ellipsoid to oblongoid, 8.0‒10.0 × 7.0‒8.0 mm, base obtuse, apex mucronate, stipes 18.0‒25.0 mm long, 1.0‒ 1.2 mm thick, glabrous. Seeds not seen.

Distribution and Ecology: —Scattered in shaded areas of tropical rain forest, in Narathiwat Province near the southern border of Peninsular Thailand, ca. 200 m alt. ( Fig. 7 ).

Phenology: —Flowering March‒April, fruiting in April and August.

Local name: —Thai: Lueang suriya.

Etymology: —The specific epithet refers to the spreading orange petals resembling the rays of the sun.

IUCN Conservation status: —Known from two localities along the southern border of Peninsular Thailand. However, there is insufficient information regarding the number of populations and population size. Therefore, the species is treated as Data Deficient (DD).

Additional specimens examined: — THAILAND. PENINSULAR: Narathiwat, Waeng District, Hala-Bala Wildlife Sanctuary , alt. 200 m, 18 March 2003 (flower), Koonkhunthod, Chasuwan & Berg 393 ( BKF) ; Narathiwat, Waeng , Bala-Hala , 3 August 1999 (fruit), Puudjaa 626 ( BKF) .

Notes: — Polyalthia heliopetala is contrasted with P. oblonga and P. motleyana in Table 1 . Turner (2014) accepted P. oblonga and P. motleyana as distinct species, but his description of P. oblonga differs sufficiently from King’s protologue that data are given separately from the two sources. For P. motleyana the description of Turner (2014) alone was used for comparison. A distinctive feature of the petals of P. heliopetala that has not been described for either of the other two species is the raised and thickened patch of tissue at the base of both the outer and the inner petals ( Figs. 1D , 2C ).

Figures

FIGURE 1. Polyalthia heliopetala: A. Habit; B. Leaf bases (upper side) and inflorescences, with point of inflorescence attachments to stem indicated by arrows; C. Flower showing recurved petals; D. Flower, top view showing the embossed patch on the inner base of the petals; E. Outer surfaces of outer petals; F. Outer surfaces of inner petals; G. Stamens and persistent sepal on pedicel; H. Torus with some stamens removed to show attachment of stamens and carpels on the convex torus surface; I. Carpel; J. Stamens (outside on left, inside on right); K. Monocarps. The illustration was drawn by Nattapong Chomlok from Leeratiwong 20-1527 (BKF).

FIGURE 2. Polyalthia heliopetala: A. Leaves and inflorescences; B. Lower surface of leaf base and flower; C. Flower showing the embossed basal patch of the inner surface of the petals; D. Upper surface of leaves and flower; E. Lower surface of leaf showing venation; F. Monocarps.A, B, D and E are from Leeratiwong 20-1527(BKF); F is from Puudjaa 626 (BKF)]; all photographs by Pasakorn Bunchalee. Photograph in C was taken by Yamilah Sama-ae in Narathiwat, Ra Ngae District, Bo Ngo Subdistrict, Bue Chaeng Village, 7 April 2020.

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.