Polyalthia khaoyaiensis P. Bunchalee & Chantar., 2019

Bunchalee, Pasakorn, Chantaranothai, Pranom, Johnson, David M. & Murray, Nancy A., 2019, Polyalthia khaoyaiensis (Annonaceae), a new species from Thailand, Phytotaxa 405 (3), pp. 171-179 : 172-177

Polyalthia khaoyaiensis P. Bunchalee & Chantar. , sp. nov., ( Figs. 1‒4 )

The species resembles Polyalthia meghalayensis Prakash & Mehrotra (1990) and Polyalthia evecta (Pierre) Finet & Gagnep. (1906) in its leaf-opposed inflorescence and inner petals that are longer than the outer petals. However, it differs from the both species in the flower pedicels only 3‒5 mm long and usually having 2 ovules per carpel. In contrast, the pedicels of P. meghalayensis are 5‒8 mm long and there is only a single ovule per carpel, rarely two. In P. evecta the pedicel is 8‒12 mm long and there is always a single ovule per carpel.

Type:— THAILAND. Nakhon Ratchasima, Khao Yai National Park , near old forest-station, alt. 800 m, 14 March 1986, Beusekom & Phengklai 45 (holotype BKF!; isotype L!) .

Habit: small to medium tree 1‒6 m high, d.b.h. 3‒7 cm, bark smooth, blackish-gray; young twigs rusty-brown pubescent, eventually glabrate, lenticels slightly prominent. Leaves: petioles 2‒4 mm long, pubescent; blade chartaceous, slightly discolorous, oblanceolate, 12‒21 × 3‒8 cm, apex acuminate, the acumen 11‒29 mm long, base asymmetrical cordate, lamina glabrous except for the pubescent midrib on upper surface and glabrate or with a few scattered hairs on lower surface; primary veins slightly impressed above, raised below; secondary veins arcuate, brochidodromous, 11‒13 veins per side, diverging from the primary vein at 60‒70º, loops curving inward 5‒7 mm from margin, slightly prominent above, raised below, intersecondary veins present; tertiary veins reticulate, indistinct on both surfaces. Inflorescence 1(‒2) flowered, morphologically terminal but appearing leaf-opposed; pedicel stout, 3‒5 mm long, rusty-brown pubescent, with a lanceolate bract adnate to the base or midpoint of the pedicel, 1‒1.5 × 1‒1.2 mm, pubescent outside and glabrous inside; buds lanceolate. Flowers with sepals valvate at base and separate at apex; outer petals separate; inner petals separate at base and valvate at apex. Sepals 3, chartaceous, ovate, valvate at base, 2‒3.5 × 2‒4 mm, apex acute, puberulous outside, glabrous inside. Petals 6 in two whorls: outer petals thinly coriaceous, pale green, ovate, apert, 4‒6 × 2‒4 mm, apex acute, puberulous outside, glabrous inside, half as long as the inner petals; inner petals thick and fleshy, oblong-lanceolate, erect, yellowish green to pale orange, tinged with pale pink toward the base on the inner surface in vivo, 9‒15(‒18) × 4‒7(‒9) mm, apex acute, puberulous outside, glabrous inside. Torus cushionshaped, 3‒4 mm in diameter, 1.5‒1.8 mm thick, hairy. Stamens cuneate, connectives pale pink at anthesis, 2‒2.4 mm long; anthers 1.5‒1.8 mm long; connective apex flat, hiding the anther locules. Carpels 25‒35 per flower, 2.8‒3.2 mm long; cylindrical, 1.8‒2.2 × 0.4‒0.5 mm, pubescent, stigma exceeding the stamens, rounded-clavate, 1‒1.2 × 0.9‒1 mm, pubescent; ovules 2 per carpel, rarely only 1, placentation lateral. Fruits: borne on a torus 3‒4 mm in diameter, 1.5‒2 mm thick, and consisting of (2‒)6‒10(‒13) monocarps, dark violet in vivo, sub-globular, apex apiculate; stalk (4.5‒) 5‒10 mm long; stipes 7‒10 mm long. Seeds 1‒2 per monocarp, sub-globular (when one seed per monocarp) or plano-convex (when two seeds per monocarp), ca. 8 mm long, 7‒7.5 mm wide, 4.5‒6 mm thick, brown, slightly shiny, slightly wrinkled, pitted on the sides; raphe/antiraphe sunken; endosperm glass-like, ruminations spiniform. Pollen grains shed in monads, bilaterally symmetrical, ovoid (surface sunken when dried), size 58‒65 × 52‒60 μm, inaperturate, verrucate.

Distribution and Ecology: — Endemic to central Thailand, distribution in hill evergreen forest, 700‒800 m alt. ( Fig. 5 ).

Phenology: _ __ Flowering from November to April and fruiting from May to June.

Local Name: ___ Thai: Tong laeng khao yai.

Etymology: ___ The species name refers to the type locality of the species.

IUCN Conservation status: — Brockelman et al. (2017) reported this species, identified as Polyalthia evecta , to be the most abundant tree in the 30-hectare Mo Singto permanent forest plot in Khao Yai National Park, with over 29,000 stems present in the plot.

This species occurs largely within a protected area, Khao Yai National Park. Moreover, the populations are quite large in certain sites and, as noted above, is the most abundant tree in the 30-hectare Mo Singto permanent forest plot, with over 29,000 stems present in the plot ( Brockelman et al. 2017, as ‘ Polyalthia evecta ’). Therefore, the species is considered to have Least Concern (LC) conservation status (IUCN Species Survival Commission, 2012); the threat to the plant’s habitat by tourist activities is considered to be low. An EOO of 87.9 km 2 and an AOO of 32 km 2 were calculated for P. khaoyaiensis , reflecting its narrow distribution.

Additional specimens examined: — THAILAND. EASTERN: Nakhon Ratchasima, Khao Yai National Park , near old forest-station, alt. ca. 800 m, Beusekom & Phengklai 45 ( BKF) ; Nakhon Ratchasima, Khao Yai , alt. 800 m, Hansen, Seidenfaden & Smitinand 11313 (C, K, L, SING) ; Nakhon Ratchasima, Khao Yai , alt. 600‒800 m, 18 March 1965, Kasem 435 ( BK) ; Khao Yai National Park , 11 April 1991, Smitinand 12-1991 ( BKF) ; Khao Yai National Park , 18 April 1991, Smitinand s.n. (BKF 141704) ; Khao Yai National Park , km 33 trail, alt. ca. 750 m, 28 November 2005, Suddee, Pedersen & Watthana 2655 ( BKF) ; CENTRAL: Nakhon Nayok, Muang District, Khao Yai National Park, 14°26´N, 101°22´E, Mo Singto area , 790 m, 22 August 2002, Boonkongchart 142 ( CMUB) ; Nakhon Nayok, Khao Fa-pa , 10 January 1969, Kasem 591 ( BK) ; Nakhon Nayok, Khao Yai National Park , 14º22´N, 101º20´E, alt. 600 m, 24 May 2002, Koonkhunthod 161 ( BKF) ; Nakhon Nayok, Khao Yai National Park, Nong Pak Chi , 14º22´N, 101º20´E, alt. 600 m, 30 June 2002, Koonkhunthod 207 ( BKF) ; Nakhon Nayok, Hin Dahng Subdistrict, Khao Yai National Park, Mo Singto area , parking area at headquarter, alt. 775 m, 23 April 2000, Maxwell 00-206 (A, CMUB, L) ; Nakhon Nayok, Khao Yai National Park , alt. 350 m, 9 August 2005, Niyomdham & Puudjaa 7537 ( BKF) ; Nakhon Nayok, Khao Yai National Park, Nature trail Haew Suwat Falls to Pha Kluei Mai Falls , 1 April 2001, Phattarathirankanok 105 ( BKF) ; Nakhon Nayok, Mueang, Khao Yai National Park, nature trail, Krong Kaeo Waterfalls to Haew Suwat Waterfalls , alt. 700 m, 14 February 2006, Poopath, Puff, Tanaros & Putthai, RP 6212 ( BKF) ; E. Khao Yai National Park, Mo Singto , alt. 700 m, 29 March 2000, Santisuk s.n. (BKF 127742) ; Nakhon Nayok, Khao Yai National Park, Mo Singto , alt. 765 m, 25 May 2002, Talo 30 ( BKF) ; Nakhon Nayok, Khao Yai National Park , Mo Singto area, Hin Dahng Subdistrict, alt. 750 m, 16 March 2002, Tanthana 16 (BKF, CMUB) ; SOUTH-EASTERN: Prachin buri, Khao Yai National Park, Haew Suwat Fall , alt. 250, 4 March 2002, Chamchumroon, Puff & Koonkhunthod V.C. 1386 ( BKF) ; Prachin Buri, Khao Yai National Park , 14°30´N, 101°30´E, alt. ca. 700 m, 18 November 1966, Hennipman 3982 (BKF, P) ; Khao Yai National Park , Prachin buri, alt. ca. 750 m, 27 March 1998, Wongprasert s.n. (BKF 123999) .

Notes: —The new species belongs to the species group of Polyalthia s.str. with terminal inflorescences that usually appear leaf-opposed. The reticulate tertiary venation, asymmetrical leaf base, absence of domatia, lateral ovule attachment, and spiniform endosperm ruminations also support its inclusion in Polyalthia . It resembles P.meghalayensis from Meghalaya State of northeastern India, but differs from that species in its larger leaves and shorter pedicels. Furthermore, the new species differs from P. meghalayensis in its oblanceolate rather than elliptic-oblong leaves and in the absence of claws on the petals. It also resembles Polyalthia evecta from northeastern Thailand, Cambodia and Laos, but has shorter pedicels and usually two ovules per carpel, and smaller outer petals but larger inner petals ( Table 1).

Brockelman et al. (2017) documented the phenology and dispersal biology of this species, identified as Polyalthia evecta . They reported the flowering period for the species to be January to June, and the fruiting period to be September and October, and that birds and gibbons were reported to be important in dispersal of the seeds.

Figures

FIGURE 1. Polyalthia khaoyaiensis: A. Side view of flower; B. Apical view of flower; C. Young monocarps; D. Mature monocarps (D photographed by Warren Brockelman).

FIGURE 2. Polyalthia khaoyaiensis: A‒C. Leaf venation patterns (upper surface). A. Middle and upper surface of leaf blade, showing the non-decurrent connection of secondary veins to primary vein, curvature of secondary veins toward margin, and intersecondary veins (arrow); B. Margin of leaf blade, showing secondary veins forming closed loops before the leaf margin; C. Asymmetrical leaf base, and reticulate tertiary veins; D. Mature monocarp, longitudinal section, showing spiniform ruminations and glass-like endosperm.

FIGURE 3. Pollen morphology of Polyalthia khaoyaiensis showing ovoid shape and verrucate ornamentation (SEM equatorial view).

FIGURE 4. Polyalthia khaoyaiensis: A. Habit of plant and position of flower on shoot; B. Flower, side view; C. Flower, basal view, showing floral part arrangement composed of 3 sepals, 3 outer petals and 3 inner petals; D. Flower, apical view, showing arrangement of two whorls of petals, stamen and carpel arrangement; E. Sepal, abaxial view; F. Outer petal, adaxial view; G. Outer petal, abaxial view; H. Inner petal, adaxial view; I. Stamen; J. Carpel; K. Habit of plant and position of monocarps on shoot; L. Leaf, adaxial view; M. Leaf, abaxial view; N. Monocarps. Drawn by Mr. S. Chansungnoen.

FIGURE 5. A & B. Location and distribution of Polyalthia khaoyaiensis in Khao Yai National Park.