Monoon namkadingense Souladeth & Tagane, 2018

Tagane, Shuichiro, Souladeth, Phetlasy, Zhang, Meng & Yahara, Tetsukazu, 2018, Flora of Nam Kading National Protected Area IV: Two new species of Annonaceae, Monoon namkadingense and Neo-uvaria laosensis, Phytotaxa 336 (1), pp. 82-88 : 83-85

Monoon namkadingense Souladeth & Tagane , sp. nov. ( Fig 1 .)

TYPE:— LAOS. Bolikhamxay Province: Nam Kading National Protected Area, 288 m elev., 18°11’56.5”N, 104°23’48.1”E, 23 December 2016, Tagane S., Yahara T., Zhang M., Okabe N., Hyakumura H., Souladeth P., Sengthong A., Chayer S. L54 [fl. & fr.] (holotype FOF!, isotypes HNL!, FU!, K, KYO!, P).

Monoon namkadingense is similar to M. simiarum (Buchanan-Hamilton ex Hooker & Thomson) Xue et al. (2012: 1033) in having greenish yellow flowers mostly along twigs behind leaves, but differs by having smaller leaves (4.5–11.6 × 1.5–3.4 cm vs. 12–20 × 5–8 cm), fewer secondary veins (6–12 vs 11–20 pairs), few-flowered inflorescences and smaller flowers (sepal up to 1.3 mm long vs. 3–5 mm long; outer petals ca. 1.3 cm long vs. 2.5–4 cm long).

Tree, 15 m tall, 66 cm in dbh. Twig densely pubelurent when young, glabrescent, grayish brown. Petiole 3–6 mm long, puberulent when young, glabrescent, blackish, concave adaxially, rounded abaxially; leaf blade elliptic, elliptic-oblong, elliptic-obovate, 4.5–11.6 × 1.5–3.4 cm, ±thickly chartaceous, dark dull greenish brown adaxially, greenish yellow and slightly glossy abaxially, glabrous, midrib sunken adaxially, prominent abaxially, glabrous, secondary veins (6–)10–12 pairs, at angle of (45º–)50º–65º from the midrib, almost flat adaxially, prominent abaxially, tertiary veins scalariform, faintly visible abaxially. Inflorescences on twigs behind leaves, sometimes on branches, single- to 3-flowered. Flowering pedicel 1.2–1.4 cm long, widening distally, covered with minute pale brown hairs, with 1 bract at or above middle point of pedicel; bracts ovate-triangular, ca. 0.8 × 0.8 mm long, densely short pale brown hairy abaxially, glabrous adaxially, apex acute, sepals 3, broadly ovate-triangular, ca. 1.3 × 2.3 mm, reflexing, outside covered with minute pale brown hairs, inside glabrous, margin ciliate, apex broadly obtuse, petals 6 in 2 whorl of 3, thickly chartaceous, oblong-oblanceolate, greenish yellow in vivo, yellowish brown when dry, apex acute, outer petals ca. 1.3 × 0.4 cm, outside ±sparsely covered with minute pale brown hairs, inside sparsely hairy except near basal 1/5 which is glabrous, inner petals slightly longer than outer petals, 1.5–1.6 × ca. 0.4 cm, hairy as in outer petals on both sides, stamens 98–108 per flower, 0.8–0.9 mm long, glabrous, anthers 0.6–0.7 mm long, connectives ca. 0.15 mm long, apex truncate, glabrous; carpels 40 per flower, ovary cylindrical, 0.5–0.6 mm long, 4-(or 5-)angular, hairy along angles, stigmas connivent cylindrical, 0.4–0.6 mm long, slightly angled, hairy only near apex. Fruiting pedicel 1.6–2.6 cm long, ca. 3 mm thick, blackish when dry, glabrous; monocarp stipe 1.6–2.6 cm long; monocarp ellipsoid, 1.6–2.5 long, 1.2–1.5 cm in diam., glabrous, reddish in vivo, blackish when dry. Seed 1 per monocarp, ellipsoid, ca. 1.4–2. cm long, 1–1.2 cm in diam., yellowish brown.

Additional specimens examined: — LAOS. Bolikhamxay Province : Nam Kading National Protected Area, 459 m elev., 18°42’37.4”N, 104°11’45.3”E, 28 June 2017, Tagane S., Souladeth P., Okabe N., Yang C.-J. L 1097 [fr.] (FOF!, FU!) ; 282 m elev., 18°10’27.5”N, 104°28’21.2”E, 26 December 2016, Tagane S., Yahara T., Zhang M., Okabe N., Souladeth P., Sengthong A., Chayer S. L411 [fl. & fr.] (FOF!); 268 m elev., 18°12’06.8”N, 104°23’18.7”E, 25 December 2016, Yahara T., Tagane S., Zhang M., Okabe N., Souladeth P., Sengthong A., Chayer S., L363 [ster.] (FOF!); 268 m elev., 18°12’06.8”N, 104°23’18.7”E, 27 June 2017, Tagane S., Souladeth P., Okabe N., Yang C.-J. L1054 [fl.] (FOF!, FU!): 258 m elev., 18°12’09.8”N, 104°23’16.1”E, 27 June 2017, Tagane S., Souladeth P., Okabe N., Yang C.-J. L1005 [fl.] (FOF!, FU!).

Distribution: — Laos, Bolikhamxay Province (so far known only from Nam Kading National Protected Area).

Habitat and Ecology: —In lowland evergreen forest, also in evergreen forest on limestone hills; 250–460 m elevation.

Phenology: —Flowering and fruiting specimens were collected both in June and December.

DNA barcodes: —GenBank accession no. LC317009 (rbcL), LC317010 (matK); we sequenced Tagane et al. L54. DNA sequences of the barcoding regions of M. namkadingense are identical with Polyalthia viridis Craib (1914: 4) [= Monoon viride (Craib) Xue et al. (2012: 1034) ] (GenBank accession no. AY319040, identities: 516/516), in rbcL, and Polyalthia lateriflora ( Blume, 1825: 20) King (1892: 58) [= M. laterifolium (Blume) Miquel (1865: 19) ] (accession no. AY518781, identities: 828/828) and Monoon kingii ( Baker, 1924: 3) Xue et al. (2012: 1032) (JX227877, 789/789) in matK.

Etymology: —The specific epithet refers to the geographical location of the find and is derived from the name of the adjacent Nam Kading National Protected Area.

Vernacular name:—ພພວນນອຍນາກະດງ (Phiphouan Noy Nam Kading, suggested here).

Primary conservation assessment: —Endangered (EN). From our collections and field observation, M. namkadingense is considered to be widely distributed in lower elevations (200–600 m) of Nam Kading National Protected Area and the area occupancy for this species is estimated to be less than 2000 km 2. Given the lowland evergreen forest is gradually cleared or selectively logged even in the protected area recently for timber collection and/or conversion to the cassava field, we suggest the category of this species as EN according to the IUCN criteria of B1a & b ( IUCN 2012).

Note: —The genus Monoon was recently reinstated from Polyalthia Blume (1830: 68) sensu lato based on chloroplast DNA sequence data and anatomical observations by Xue et al. (2012). It consists of ca. 60 species distributed in tropical and subtropical Asia, from India to Japan, extending to Australia. Whereas several species are known in surrounding countries: 13 species from Thailand ( Pooma & Suddee 2014), eight species from Vietnam ( Ly 2017), two species from Cambodia ( Finet & Gagnepain 1907), five species from China ( Li & Gilbert 2011), and only one species of Monoon , M. simiarum has been known from Laos ( Newman et al. 2007, Xue et al. 2012). Monoon nankadingense is easily distinguished from the other species in neighboring areas by a combination of its relatively smaller leaves less than 11.6 cm long, fewer secondary veins, solitary to 3-flowered inflorescences produced on twigs behind leaves, sometimes on branches and 1.2–1.4 cm long flowering pedicels.

Figures

FIGURE 1. Monoon namkadingense Souladeth & Tagane. A) Habit, B) Flowering twig, C) Top branch, D) Portion of lower leaf surface, E) Flowering (above) and petals-dropped flower after anthesis (below), F) Flower, G) Stamens and carpels, H) Monocarps, I) Bracteole, J) Sepal, K) flower petals and some stamens removed, L) Outer petals (left three) and inner petals (right three), M) Stamens, N) Carpels. Materials (I–N) from Tagane et al. L54 (FU). Scale bars I, M & N = 5 mm; J & K = 1 mm; L = 1 cm.