Polyalthia chantaranothaii P.Bunchalee & Chalermglin, 2021

Bunchalee, Pasakorn, Johnson, David M., Murray, Nancy A. & Chalermglin, Piya, 2021, Three new species of Polyalthia (Annonaceae) from Thailand and Laos, Phytotaxa 512 (4), pp. 272-282 : 276-279

Polyalthia chantaranothaii P.Bunchalee & Chalermglin , sp. nov. ( Figs 3 , 4 )

Type:— THAILAND. Lampang, Me Ping, 200 m, 21 June 1926, Winit 1708 (holotype BK 201002 !; isotype BKF!) .

Polyalthia chantaranothaii resembles Polyalthia intermedia and P. suberosa in its short habit and mostly solitary flowers on leaf-opposed inflorescences, but it differs from both species because the primary leaf vein is flat or raised rather than grooved on the upper side and the pedicel is 4.0–6.0 mm rather than 10.0–30.0 mm long. In addition, P. chantaranothaii differs from P. intermedia in its cordate rather than acute leaf base and from P. suberosa in its acuminate leaf apex and oblong inner petals, whereas the leaf apex of P. suberosa is shallowly retuse, obtuse or acute, and the inner petals are obovate.

Small shrubs 0.5–3.5 m tall, d.b.h. up to 3.5 cm, primary branching spiral; bark smooth, blackish gray. Twigs initially brown erect-puberulous, lenticels conspicuous. Leaves subsessile, the petioles 1.0–2.0 mm long, 0.8–1.0 mm thick, grooved on the upper side, erect-puberulous; lamina symmetrically oblanceolate or elliptic, 7.5–14.0 × 2.5–4.5 cm, base asymmetrically cordate with auricles 0.7–1.0 mm long, apex acuminate with acumen 10.0–15.0 mm long, upper side glabrous, lower side appressed-puberulous; midrib flat to raised above, puberulous; lateral veins curved towards the apex, 8−10 veins per side, attached excurrently to midrib at 65–75º, brochidodromous, curving inward 3.0–5.0 mm from margins; interlateral veins present; tertiary veins reticulate. Inflorescences 1(−2)-flowered, leaf-opposed or supraaxillary, lacking peduncle and rachis; pedicels 4.0–6.0 mm long, 0.4–0.5 mm thick, brown appressed-puberulous; bract acute, ca. 0.5 × 0.5 mm, attached to middle of pedicel, appressed-puberulous outside and glabrous inside; buds ovoid. Sepals pale green at anthesis, ovate, valvate, 2.0–2.5 × 2.0– 2.5 mm, apex acute, appressed-puberulous outside, glabrous inside. Petals 6 in 2 whorls, appressed-puberulous outside, glabrous inside; outer petals pale yellowish green in vivo, valvate, ovate, 2.0–2.5 × 3.0– 3.5 mm, apex acute; inner petals pale yellow on both sides or pale pink towards the base inside in vivo, valvate, thicker than the outer petals, oblanceolate to oblong, 8.0–10.0 × 3.0– 4.5 mm, apex acute. Stamens pale yellow at anthesis, clavate, 0.9–1.2 × 0.6–0.9 mm; anthers 0.8–1.0 mm long; anther connective apex truncate; androecium 4.0–5.0 mm in diameter. Carpels 10–15 per flower, 1.4–1.6 × 0.4–0.5 mm, appressed-pubescent; stigma subsessile, globose, 0.4–0.5 mm in diameter, erect-puberulous, higher than anther connective apices; 1(–2) ovule per carpel. Torus thickly cushion-shaped and truncate, 1.8–2.0 mm in diameter, 0.8–1.0 mm thick, glabrous. Fruits of up to 8 monocarps borne on a pedicel 8.0–12.0 mm long, 0.6–0.7 mm thick; monocarps dark red at maturity, subglobose or oblong, 5.0–6.0 mm in diameter, glabrous, apex apiculate, stipes 2.0–4.0 mm long, 0.6–0.7 mm thick; seed 1(–2) per monocarp, subglobose, 4.0–5.0 mm in diameter, surface smooth and surrounded by a longitudinal groove, brown, shiny; endosperm ruminations spiniform, endosperm glass-like.

Ecology: —Scattered along streams and waterfalls in mixed deciduous forest or dry evergreen forest at 200– 850 m.

Phenology: —Flowering March–May, fruiting May–August.

Local name: —Thai: tong laeng doi (ต้องแล่งดอย); nom noi (นมน้อย) (Phitsanulok).

Etymology: —In honour of Pranom Chantaranothai, Thai professor of botany and benefactor of many plant taxonomists, who assisted the first author in analyzing the morphology of this species.

Conservation status: —The species occurs in a small area of northern and northeastern Thailand and adjacent Laos PDR. Distribution has been changed by human activities, but the species should be regarded as Data Deficient because many of the localities have not been re-investigated recently.

Additional specimens examined: — THAILAND. Northern : Chiang Mai, SE foothills above Ban Yang Pong Luang, Doi Chiang Dao, Chiang Dao , 550 m, 27 May 1989, Maxwell 89-678 ( BKF, CMU, L.1763039) ; Nan, Baan Luang , 450 m, 4 Aug 1998, Maxwell 98-795 ( BKF) ; Lampang, Wang Nuea, Doi Luang N. P., Wangkaew Falls , 600 m, 23 Apr 1997, Maxwell 97-403 ( BKF, CMUB, L.1763030) ; Phitsanulok, Chat Trakan, Phumiang-Phuthong Wildlife Sanctuary , 500 m, 17 June 2010, Romklao Botanical Garden 0062/2553 ( QBG) . Northeastern : Loei, Wang Sapung, Phu Luang , 9 Aug 1976, Bunnak 3142 ( BKF) ; Loei, interior of Nam Thop, on eastern slope of Phu Luang , 400−850 m, 7 Dec 1965, Tagawa, Iwatsuki & Fukuoka T-1943 ( BKF, KYO) . LAOS. Vientiane: Muang Baw , 300 m, 27 Apr 1932, Kerr 21276 ( BK, L.1768110) .

Notes: —The outer petals of Polyalthia chantaranothaii are the shortest of any species in the P. evecta complex. The distribution of P. chantaranothaii differs from that of its most similar congeners: Polyalthia intermedia is restricted to the Khorat Plateau of eastern Thailand and extends into Cambodia and Vietnam; Polyalthia suberosa , a widespread Southeast Asian species, is found throughout Thailand.

We could not precisely locate Muang Baw, Laos, reported as the collecting area for Kerr 21276 ( BK). Jacobs (1962) indicated that Kerr 21249–21298 were made along a southeastern route between Pu Lawek and Borikan, via Nam Yak , Muang Baw , and Hat Kam , an area northeast of the city of Vientiane. ( Jacobs gives the coordinates for Pu Lawek as 18°46’N, 103°14’E.)

Figures

FIGURE 3. Polyalthia chantaranothaii: A. Habit; B–E. Young branches and flowers; F. Immature monocarps; G & H. Leaf venation in midrib zone (upper side and lower side, respectively); I & J. Leaf base (upper side and lower side, respectively); K. Leaf venation on marginal zone. Photographs taken by Pasakorn Bunchalee.

FIGURE 4. Polyalthia chantaranothaii: A. Flowering branch; B & C. Petiole and leaf base (upper side and lower side, respectively); D–F. Flowers. G. Stamen, outside (left), inside (right); H. Carpel; I. Sepal, outside (left), inside (right); J. Outer petal, outside (left), inside (right); K. Inner petal, outside (left), inside (right). Illustration by Wipawan Kiaosanthie.