Elatostema kaweesakii Triyutth. & L.F.Fu, 2022

Triyutthachai, Natthawut, Fu, Long-Fei, Triboun, Pramote, Wei, Yi-Gang & Pornpongrungrueng, Pimwadee, 2022, Three new species of Elatostema (Urticaceae) from Thailand, PhytoKeys 215, pp. 37-50 : 37

1. Elatostema kaweesakii Triyutth. & L.F.Fu sp. nov.

Figs 1 , 2

Diagnosis.

Elatostema kaweesakii is similar to E. atroviride W.T. Wang but differed by its large swollen rhizome, staminate inflorescences with 2-7 cm long peduncle, receptacle rectangular, glabrous, staminate flower with 5 ovate tepals, pistillate inflorescences with 5-10 mm long peduncle, receptacle rectangular, glabrous, pistillate flower without tepals, staminode present and achene smooth (Table 1 ).

Type.

Thailand. Loei: Nong Hin district , 17°7.3'N, 101°56.05'E, 360 m alt., 9 August 2022, Triyutth. 332 (holotype KKU!; isotypes AAU!, BKF!) .

Description.

Perennial herbs, lithophytic, monoecious, rhizomatous. Rhizome rounded, 2-20 cm in diam., brownish. Stems 15-50 cm tall, simple or branched, succulent, greenish, glabrous. Stipules 2, persistent or sometimes caducous in reproductive stage, linear or lanceolate, 4-7 × 1-3 mm, membranous, glabrous. Nanophylls absent. Leaves distichous, alternate; petiole 0.5-1 cm long, greenish, glabrous; lamina asymmetrically ovate to elliptic, 5-20 × 3-10 cm, base oblique, margin serrate to dentate, apex acuminate, chartaceous; venation pinnate, major basal lateral veins present; upper and lower surfaces greenish, glabrous, cystoliths fusiform, 0.2-0.5 mm long. Staminate inflorescences axillary, solitary, capitate, 1.5-2.0 cm in diam.; peduncle 2-7 cm long, glabrous or pubescent; receptacle rectangular, 0.6-1.0 × 0.6-1.0 cm, chartaceous, glabrous; bracts ovate, connate at base, membranous, glabrous; bracteoles lanceolate, 0.6-0.8 × 0.2-0.3 mm, membranous, pubescent. Staminate flowers 80-100 per inflorescence, sessile to subsessile, glabrous; tepals 5, ovate, 1.0-1.5 × 1.0-1.5 mm, apex acuminate, membranous, pubescent; stamens 5, filaments 1.0-1.5 mm long, anthers 0.6-0.8 mm long. Pistillate inflorescences axillary, solitary, capitate 5-10 mm in diam., peduncle 0.5-1.0 cm long, glabrous; receptacle rectangular, 6-8 × 6-8 mm, chartaceous, glabrous; bracts ovate, 0.8-1.0 × 0.5-0.6 mm, membranous, pubescent; bracteoles lanceolate, 0.4-0.6 × 0.2-0.3 mm, membranous, pubescent. Pistillate flowers 40-100 per inflorescence, sessile to subsessile, glabrous; tepals absent; staminodes 3, oblong to linear, 0.2-0.3 mm long; ovary superior, ovoid, 0.3-0.5 mm long. Achenes ellipsoid, 0.8-1.2 mm long, brownish, smooth.

Distribution.

Currently known only from Loei province in northeastern Thailand.

Ecology.

Occur in limestone crevices.

Phenology.

Flowering and fruiting in April-December.

Etymology.

This species is named in honor of Mr Kaweesak Keeratikiat, who first discovered the plants.

Conservation status.

This species was found in fewer than 5 locations at Nong Hin district, Loei province, Thailand. Moreover, it has a very small population and very restricted distribution, and the number of mature individuals is fewer than 250. According to IUCN (2022) this species should be assessed as Endangered (EN) under IUCN criteria B2a and D1.

Additional specimens examined.

Thailand. Loei: Nong Hin district , 16 December 2013, S. Saengvirotjanapat 635 (QBG!), ibid., 20 April 2021, Triyutth. 329 (KKU!) .

Notes.

This species is similar to E. atroviride in their habitat as lithophytes growing in limestone crevices. Both species have rounded rhizome, absence of nanophyll and a similar shape of leaves. However, it differs from E. atroviride by several characters such as its large rounded rhizome (small size of rhizome in E. atroviride ), staminate inflorescences with 2-7 cm long peduncle (vs 2-5 mm long), receptacle rectangular and glabrous (vs elliptic and pubescent), staminate flower with 5 tepals (vs 4 tepals), pistillate inflorescence with 5-10 mm long peduncle (vs 2-4 mm long), absence of tepals in pistillate flower (vs 3 tepals), 3 staminodes (vs staminode absent) and achene smooth (vs 6-8 ribbed).

Figures

Figure 1. Elatostema kaweesakii Triyutth. & L. F. Fu, sp. nov. A habit B staminate inflorescence C staminate flower D pistillate inflorescence E pistillate flower F bracteole G achene (Drawn by N. Triyutthachai).

Figure 2. Elatostema kaweesakii Triyutth. & L. F. Fu, sp. nov. A habit and habitat B pistillate inflorescence C staminate inflorescences (Photos A, C by K. Keeratikiat, B by Triyutth).