Lasianthus sithammaratensis Napiroon, Balslev & Chayamarit, 2020

Napiroon, Tiwtawat, Chayamarit, Kongkanda, Dawson, Sally, Till, Walter & Balslev, Henrik, 2020, A synopsis of Lasianthus (Lasiantheae, Rubiaceae) in Thailand and two additional new species, Phytotaxa 439 (1), pp. 1-38 : 30

58. Lasianthus sithammaratensis Napiroon, Balslev & Chayamarit , sp. nov. ( Figure 2 ).

Diagnosis:— Lasianthus sithammaratensis is morphologically similar to L. appressus Hooker (1880:181) , but differs by having: leaves that are oblong or oblong-lanceolate (not lanceolate), 8‒10 × 1.5‒2 (not 6‒8 × 2‒3) cm; 10–12 (not 6–8) pairs of secondary veins; pubescent (not appressed-hirsute) on the branches, stipules, bracts and calyx; conspicuous (not inconspicuous) stipules that are 2.5‒3 (not 0.5‒1) mm long; petioles 10‒11 (not 4‒5) mm long; bracts absent (not present and linear-lanceolate to subulate); calyx cupular (not campanulate); corolla tube sparsely hirsute outside, pilose inside (not pubescent on both sides); drupes subglobose (young drupes on specimens), pubescent (not glabrous); 4‒5 (not 8) pyrenes.

Type:— THAILAND. Nakhon Si Thammarat: Khao Maen, Nam Tok Yong National Park, 8 ° 17’42”N, 99 ° 39’47”E, 9 February 2005, K. Williams 1319 (holotype: WU!).

Description:—Shrubs 30‒40 cm tall. Stem terete, 0.6–0.8 cm diam., subglabrous; branches and branchlets terete, 5–6 mm diam., puberulous. Stipules conspicuous, broadly-triangular and persistent when dry, 2.5‒3 mm long, apex acute, pubescent. Leaves coriaceous; petiole 10‒11 mm long, pubescent; blades oblong or oblong-lanceolate, 8–10 × 1.5–2 cm, base acute, apex acute, glabrous on both surfaces, pubescent on the midrib and veins beneath; secondary veins 10–12 pairs, slender, slightly depressed above, prominent beneath, ascending at angles of 45‒50° from midrib, tertiary veins concealed above, obvious beneath, parallel or subreticulate; bracts absent. Cymes sessile; calyx pubescent, cupular; calyx tube 4 mm long; calyx 4-lobed, lobes broadly-triangular, 0.8–1 mm long; corolla 7 mm long, corolla tube 5 mm long, outside sparsely hirsute and inside pilose, 5-lobed, lobes lanceolate 3 mm long, externally sparsely hirsute, internally pilose; anthers 5, innate, 0.8–1 mm long; style 3 mm long, 5 lobed, glabrous, stigma 0.8–1 mm long. Drupes subglobose (only young drupes present on specimens), puberulous, fresh fruit purple-green, crowned by calyx limb; pyrenes 4‒5, very hard.

Common name: —Pat Muang Si Thammarat.

Distribution: —Endemic to Peninsular Thailand in moist evergreen forest at Khao Maen, Nam Tok Yong National Park in the Nakhon Si Thammarat province.

Habitat: — Growing under shade among understory trees in scrub forest, on sandy-loam at 100‒120 m elevation.

Proposed IUCN conservation assessment: — Lasianthus sithammaratensis is here assessed as Endangered (B2ab(ii)), in accordance with IUCN criteria ( IUCN 2012). It is known only from one population in Nam Tok Yong National park, Nakhon Si Thammarat province.

Phenology: — Flowering and fruiting in February–March.

Etymology: —The specific epithet refers to the type locality which is in Nakhon Si Thammarat province, southern Thailand where it is commonly known as Nakhon or Si Thammarat.

Figures

FIGURE 2. Lasianthus sithammaratensis (from holotype K. Williams 1319, WU!). A. Habit showing leaf arrangement, B. Inflorescences and stipule, C. Calyx, note cupular shape, D. Mature flower split opened, E. Flower with calyx. Illustration by Ms.Wanwisa Bhuchaisri.