Lasianthus yalaensis Napiroon, Duangjai & Poopath, 2018

Napiroon, Tiwtawat, Poopath, Manop, Duangjai, Sutee, Balslev, Henrik & Vajrodaya, Srunya, 2018, Lasianthus yalaensis (Rubiaceae), a new species from peninsular Thailand, Phytotaxa 364 (2), pp. 172-180 : 175-177

Lasianthus yalaensis Napiroon, Duangjai & Poopath , sp. nov. ( Figs. 1 , 2 )

Lasianthus yalaensis Napiroon, Duangjai & Poopath is morphologically similar to Lasianthus pilosus Wight (1846: 506) , but it differs in having lanceolate stipules (vs triangular-lanceolate), small leaves 5–8 × 2–2.5 cm (vs 8.0–17.0 × 3.5–6.0 cm), 7–8 pairs of secondary veins (vs 9–15 pairs), strigose indumentum on the leaf blade, midrib, branches, stipules, bracts and calyx (vs pilose), cupular calyx (vs tubular), 2 ‒ 3 mm, triangular lobes, (vs 5–6 mm, linear), and calyx limb on fruits with short lobes 1.0 mm long (vs 2.0–3.0 mm).

Type:— THAILAND. Yala, Betong, Ban Chulabhorn Phattana 10, 5 ° 51’28.9”N, 101 ° 14’13.7”E, 1 February 2015, M. Poopath, V. Chamchumroon, J. Wai, K. Khammongkol, & S. Jirakorn 876 (holotype: BKF!, isotype: PSU!).

Shrubs up to 1 m tall. Stem terete, 1.5–2 cm diam., strigose; branches and branchlets terete, 1–2 mm diam., strigose, hairs 5–7 mm long. Stipules lanceolate and persistent when dry, apex acute, densely strigose, 5–7 mm long. Leaves chartaceous to subcoriaceous; petiole 0.5 mm long, densely strigose; blades elliptic or oblong, 5–8 × 2–2.5 cm, base rounded, apex acuminate to slightly subcordate, asymmetric or oblique, strigose on both surfaces, more densely so on the midrib and veins beneath; secondary veins 7–8 pairs, slender, slightly depressed above, prominent beneath, ascending at angles of 45° ‒ 50° from midrib, tertiary veins concealed above, obvious beneath, reticulate or netted; bracts small, 4–10 mm long, filiform, strigose. Cymes sessile; calyx strigose, cupular; calyx tube 1–1.5 mm long; calyx 5-lobed, lobes triangular, 1–1.5 mm long, margin strigose; corolla 2.5–3 mm long, corolla tube 2 mm long, outside hirsute and inside glabrous, 5-lobed, lobes triangular 0.5–1 mm long, externally hirsute, internally glabrous; anthers 5, innate, 0.5–0.8 mm long; style 2 mm long, 5 lobed, glabrous, stigma 0.8–1 mm long. Drupes globose, 4–5 mm diam., sparsely strigose, crowned by calyx limb with 1 mm long hair; pyrenes 5, very hard.

Additional specimen examined: — THAILAND. Yala, Betong, Ban Chulabhorn Phattana 10, 11 June 2005, [ V. Chamchumroon & M. Poopath 2191 ( BKF!, PSU!)], Songkhla, Na Thawi, Sankalakiri National park, 9 April 2018, [ T. Napiroon, M. Poopath, V. Chamchumroon & S. Jirakorn 027 ( BKF!, PSU!)].

Common name: —Jed Chang Sarn Noi Yala.

Distribution: —Endenic to Peninsular Thailand, known from Betong district, Yala province, Nathawi district, Songkhla province and it may occur in northwestern peninsular Malaysia close to the border of Thailand and Malaysia.

Habitat:—Growing in shade among understory trees in tropical rainforest, on metamorphic or granitic rock substrates at 400 ‒ 1,000 m elevation. This species was found from the foothills to ridges at 500–1000 m elevation.

Proposed IUCN conservation assessment: — Lasianthus yalaensis is here assessed as Endangered (B2ab(ii)), in accordance with IUCN categories and criteria ( IUCN, 2012). It is known from two populations in Betong district, Yala province and its occupancy area is estimated to be less than 500 km 2. These forests are not protected and may be devastated by agricultural activities extending nearby. The distribution of these plants is suspected to be declining.

Phenology:—Fruiting stage: February–March.

Etymology: —The specific epithet refers to type locality which is in Yala province, southern Thailand.

Molecular phylogeny:— The Bayesian tree is congruent with that inferred from maximum parsimony (tree not shown). The MP analysis resulted in 15 equally parsimonious trees with 2894 steps (CI= 0.60, RI=0.81, RCI=0.49). Bayesian and parsimony analyses of the combined data sets from this study are congruent with those reported in Smedmark et al. (2014) and support monophyly of Lasianthus . There are two well-supported clades within the genus Lasianthus namely the Asian clade and the African/Neotropical clade. The molecular data confirm the placement of the new species ( L. yalaensis ) in the Lasianthus and showed its phylogenetic relationships ( Fig. 3 ). Lasianthus yalaensis belong to the Asian clade and is closely related to L. pilosus Wight (1846: 506) , L. congesticymus H. Zhu (2001: 124) , L. scalaris Craib (1933: 26) , and L. ellipticus Wight (1846: 507) (PP=1.00, BP=80%). The new species is sister to L. pilosus . Results from molecular analyses based on nuclear and plastid markers also support the recognition of L. yalaensis as a distinct species (PP=1.00, BP=100%). Additionally, DNA sequences of a new species show substantial differences from the closest species ( L. pilosus ) and the details of its species-specific position showed in Supplementary Table 2 to Table 4. DNA sequences of the new species (Collector no. M. Poopath et al. 876 and 906) were submitted to the Genbank. The Genbank accession numbers refer to supplementary Table 1.

Figures

FIGURE 1. Lasianthus yalaensis (from holotype Poopath et al. 876, BKF!). A. Leaf arrangement and strigose branches, B. Abaxial side of leaf blade showing reticulate or netted veins, C. Calyx, D. Fruit position, E. Stipule and bracts, F. Drupe with persistent calyx on crown, G. Young flower split opened. Illustrated by Ms.Wanwisa Bhuchaisri.

FIGURE 2. Lasianthus yalaensis.A. Leaf arrangement, B. Habit, C. Indumentum strigose on branch, D. Stipule and bracts covered with strigose indumentum, E. Drupe crowned by persistent calyx. Photographs:A by M. Poopath and B–E by T. Napiroon (Poopath et al. 876, BKF)

FIGURE 3. Phylogenetic position of Lasianthus yalaensis (in bold font) inferred from Bayesian analysis of the combined data set of four DNA regions (rps16, trnTLF, ITS, ETS). Bayesian posterior probabilities and bootstrap values are indicated at each node. The clade referred to in the text is indicated to the right.