Capparis lianosa Fici & Souvannakhoummane, sp. nov (Figs 2; 3) A C. zeylanica L. spinis stipularibus minoribus, foliis cum apice acuminato, petalis brevioribus, gynophoro breviore glabro vel glabrescente, stigmate plano praecipue differt. TYPUS. — 115° Lao PDR, Luang120° Prabang Province, Muang Ngoi Neua, evergreen forest on limestone, 510 m, 17.III.2019, Fici et al. 1911 (holo-, PAL!). PHENOLOGY. — Flowering in March-April. DISTRIBUTION AND ECOLOGY. — The new species is only known from the type locality (Fig. 1), where few scattered individuals were observed in the evergreen forest at the top of a Permo-Carboniferous limestone formation, with Dracaena cambodiana Pierre ex Gagnep., Euphorbia antiquorum L., Ficus sp., Schefflera pueckleri (K. Koch) Frodin, Platycerium holttumii Joncheere & Hennipman, Asplenium nidus L. var. nidus (Fig. 3); 410-510 m a.s.l. CONSERVATION STATUS. — Following the IUCN Red List Categories and Criteria (IUCN 2012), the new species is here assessed as Vulnerable (VU D1) due to its restricted area of occupancy, in a single location so far known, and low number of individuals observed. However due to the inaccessibility of most limestone outcrops in the area, its population size is possibly larger. DESCRIPTION Large woody climber up to c. 20 m long. Stem to 15 cm diameter bearing knobs with thorns; twigs pubescent with dense, simple, greyish hairs mixed with stellate, reddish or greyish hairs. Stipules Stipular thorns recurved 1.5-2.5 mm long, pubescent. Leaves Petioles sulcate, 0.6-1 cm long, pubescent. Leaf blades ovate or elliptical, wider at or below the middle, (2.3-) 2.5-2.8 times as long as wide, (9.5-) 11-13.6 × (4-) 4.4-5.5 cm; base acute; apex obtuse or rounded, acuminate with tip 3-5 mm long; mature leaves with upper surface glabrous, lower surface mostly glabrous, sparsely pubescent along the midrib and lateral veins, young leaves pubescent on both surfaces; veins c. 4-5 on each side of the midrib, thin, decurrent along the margin. Flowers Flowers serial; pedicels 0.6-1.3 cm long, pubescent. Sepals acute, densely pubescent outside and at margins, glabrous inside, outer pair boat-shaped, coriaceous, 7 × 4-6 mm, inner pair thinner, 5-6 × 3-3.5 mm. Petals oblong, white or yellowish, 7-9 × (2.5-) 3-4 mm, pubescent at margins and inside, glabrous outside. Stamens c. 37-40; filaments (1.4-) 1.8-2.2 cm long, pink or reddish; anthers basifixed, c. 1 mm long. Gynophore 1.9-2.3 cm, white, pink or reddish in the available material, glabrous or glabrescent; ovary ovoid or ellipsoid, 1.5-2 × 1-1.5 mm, glabrous, with flattened stigma. Fruit Unknown. REMARKS Capparis lianosa, sp. nov. belongs to sect. Monostichocalyx, which includes several species in south-eastern Asia. It is mainly distinguished from related taxa by its short stipular thorns, leaves ovate or elliptical with base acute and apex shortly acuminate, petals pubescent inside, gynophore glabrous or glabrescent and ovary with flattened stigma (Figs 2, 3). With regard to the lianous habit, the length of stems – up to c. 20 m – of the new species appears noteworthy if considering the available data for other climbing species of sect. Monostichocalyx (Jacobs 1960, 1965). C. lianosa, sp. nov. resembles in the habit and indumentum C. zeylanica L., a species showing wide distribution from India eastwards to the Philippines and Indonesia, which however differs in qualitative characters as the gynophore hairy at the base and the stigma elongate (Jacobs 1965). Furthermore in C. zeylanica the stipular thorns are 3-6 mm long, leaf-blade is 4-10 (–18) cm long, with base rounded or subcordate, rarely acute and apex acute or rounded, rarely slightly acuminate, with a stiff, recurved mucro, petals are 9-12 (–19) mm long, anthers are 1.6-2 mm long and gynophore is (2–) 4-5 (–6.5) cm long (Table 1). C. lianosa, sp. nov. shows also affinities with C. acutifolia Sweet, a species widespread from India to southern China, Taiwan and Vietnam, which mainly differs in the thorns straight or wanting, leaf apex more markedly acuminate, lower number of stamens (<35), gynophore filiform and ovary pear-shaped (Table 1). Some other species of sect. Monostichocalyx recorded in southeastern Asia and characterized by innovations hairy with often reddish stellate hairs and flowers serial in supra-axillary rows (Jacobs 1965), as C. pyrifolia Lam., C. urophylla Chun, C. tenera Dalz. and C. echinocarpa Pierre, can be easily distinguished from C. lianosa by the shorter sepals (up to c. 5 mm long) and by the lower number of stamens (up to 20) (Table 1). The Central Indochina limestone karst ecoregion, represented in Lao PDR and Vietnam (Inthakoun & Delang 2008), is a relevant centre of differentiation for the genus Capparis. In Lao PDR most species of this genus are linked with carbonatic substrata and three new species have been recently described from the Khammouan karst (Fici et al. 2018, 2020; Souvannakhoummane et al. 2018).

Published as part of Fici, Silvio & Souvannakhoummane, Keooudone, 2020, Studies on the genus Capparis L. (Capparaceae) in Lao PDR. V: A new species from limestones of the Luang Prabang Province, pp. 113-118 in Adansonia 42 (5) on pages 114-117, DOI: 10.5252/adansonia2020v42a5, http://zenodo.org/record/3877381