Polyalthia chayamaritana P.Bunchalee & N.A.Murray, 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 : 279

Polyalthia chayamaritana P.Bunchalee & N.A.Murray , sp. nov., ( Figs. 5 , 6 )

Type:— THAILAND. Roi Et, Nongpok Dist., Phu Khiao , Tham Pha Nam Thip Non-Hunting Area , 16° 23´40.55˝ N, 104° 18´37.16˝ E, 375 m, 17 Aug 2015, Puudjaa, Rueangruea & Hemrat 1897 (holotype BKF210578 !) .

Polyalthia chayamaritana resembles P. cinnamomea in petiole length, leaf shape, and axillary inflorescences but differs in being a short tree with the primary leaf vein flat on adaxial surface, inflorescence with a distinct peduncle and rachis, narrowly lanceolate to linear-lanceolate petals 13.0–25.0 × 2.0–4.0 mm, and 2 ovules per carpel. In contrast, P. cinnamomea is a medium to tall tree with the primary vein grooved on the adaxial surface, inflorescence lacking a peduncle and rachis, linear petals 55.0–90.0 × 3.0–7.0 mm, and 4 ovules per carpel.

Small trees 1.0–3.0 m tall, d.b.h. up to 3.5 cm, primary branching spiral; bark smooth, blackish gray. Twigs rusty brown erect-tomentose, lenticels moderately conspicuous. Leaves with petioles 4.0–5.0 mm long, 1.8–2.0 mm thick, grooved above, erect-tomentose; lamina symmetrically narrowly elliptic, 13.0–22.0 × 3.0– 5.5 cm, base asymmetrically cordate with auricles 0.3–0.5 mm long, apex acute, upper side glabrous, lower side erect-puberulous; midrib flat above, densely erect-pubescent; lateral veins curved towards the apex, 14–16 veins per side, attached excurrently to midrib at 65–70º, mixed eucampto/brochidodromous, curving inward 2.0–4.0 mm from margins; interlateral veins present; tertiary veins weakly percurrent. Inflorescences 1–2(–4)-flowered, axillary on leafy twigs or on woody tubercles of trunk or leafless twigs, peduncles 1.0−2.0 mm long; rachis 2.0−4.0 mm long, 1.5−2.0 mm thick; pedicels 1.0–2.0 mm long, 1.2−1.5 mm thick, brown erect-tomentose; bract lanceolate, 3.5–5.0 × 2.0– 2.5 mm, attached at the pedicel base, appressedtomentose outside, glabrous inside; buds lanceoloid. Sepals pale brown, ovate, valvate, 4.0–5.0 × 3.5–4.5 mm, apex acute, appressed-tomentose outside, glabrous inside. Petals 6 in 2 whorls, pale greenish brown to pale pinkish brown or pale greenish white in vivo, narrowly lanceolate, valvate, appressed-tomentose outside, glabrous inside; outer petals 14.0–25.0 × 3.0–4.0 mm, apex acute; inner petals 13.0–23.0 × 2.0– 2.5 mm, apex acute. Stamens pale creamy white at anthesis, cuneate, 1.3−1.5 × 0.8−1.0 mm; anthers 1.0– 1.2 mm long; anther connective apex truncate; androecium 4.0– 4.5 mm in diameter. Carpels 7–20 per flower, 1.8–2.0 × 0.4–0.5 mm, appressed-pubescent; style subsessile; stigma globose, 0.4–0.5 mm in diameter, erect-puberulous, higher than anther connective apices; ovules 2 per carpel. Torus convex and truncate, 1.8–2.0 mm in diameter, 1.0– 1.2 mm thick, glabrous. Fruits of up to 12 monocarps borne on a pedicel up to 10.0 mm long, 1.8–2.0 mm thick; monocarps brown when ripe, subglobose or oblongoid, 8.0–12.0 × 8.0–10.0 mm, appressed-tomentose, apex blunt, stipes 1.0–2.0 mm long, 0.8–1.0 mm thick. Seed 1(–2) per monocarp, subglobose or strongly biconvex, discoid, 6.0–8.0 mm in diameter, surface pitted and surrounded by a longitudinal groove, light brown, shiny; endosperm ruminations spiniform, endosperm glass like.

Ecology: —Known only from moist mountain slopes in dry evergreen forest at 250–375 m.

Phenology: —Flowering February−March and August, fruiting March–June and August.

Local name: —Thai: thon ammarit (ต้นอัมฤทธิ์).

Etymology: —In honour of Kongkanda Chayamarit, expert on the Thai flora and executive editor of the Flora of Thailand project.

Conservation status: —The conservation status is proposed as Data Deficient. Polyalthia chayamaritana is only known from the eastern Khorat Plateau, in the Tham Pha Nam Thip Non-Hunting Area, Nongpok District, Roi Et Province.

Notes: — Polyalthia chayamaritana has distinctive pale pink guava-scented wood, a feature shared with Polyalthia cinnamomea , a species distributed from Peninsular Thailand southward. Polyalthia chayamaritana is the only cauliflorous Polyalthia species known from the Khorat Plateau.

Figures

FIGURE 5. Polyalthia chayamaritana:A. Habit; B & C. Inflorescences on trunk and branches; D. Leaves; E. Leaf bases; F. Inflorescence, showing peduncle and rachis; G. Monocarps; H. Seed (side view); I. Seed (micropylar view); J. Leaf venation patterns in midrib zone; K. Leaf venation in marginal zone; L. Stamen, outside; M. Carpel. Photographs taken by Pasakorn Bunchalee.

FIGURE 6. Polyalthia chayamaritana: A. Leaves, lower side (left), upper side (right); B & C. Flowers (B. younger, C. older); D. Sepal, outside (left), inside (right); E. Outer petal, outside (left), inside (right); F. Inner petal, outside (left), inside (right); G. Stamens, outside (left), inside (right); H. Carpel; I. Monocarps; J. Mature monocarp containing two seeds; K.Young monocarp containing one seed; L. Seed, micropylar view; M. Seed, lateral view. Illustration by Orathai Kerdkaew.