Cyphostemma calcarium Rabarij & L.M.Lu, 2021

Rabarijaona, Romer Narindra, Rafaralahy, Valisoa Louisicael, Rakotovao, Charles, Ranaivoson, Rindra Manasoa, Liu, Bing, Chen, Zhi-Duan, Wen, Jun & Lu, Li-Min, 2021, Cyphostemma calcarium, a new species of Vitaceae from the Ankarana Special Reserve, Madagascar, PhytoKeys 180, pp. 73-80 : 73

Cyphostemma calcarium Rabarij & L.M.Lu sp. nov.

Figs 2 , 3

Diagnosis.

Cyphostemma calcarium is most closely comparable to C. rutilans Desc. in morphology. It differs from the latter in having distinct pubescent branches (vs. branches entirely glabrous in C. rutilans ); leaves minutely puberulous and shiny on the adaxial surface, abaxial surface densely whitish pubescent to velvety particularly on the veins (vs. leaves entirely glabrous and shiny on both sides in C. rutilans ); and leaflets broadly oblong or elliptic, base cuneate (vs. leaflets narrowly ovate, base subcordate in C. rutilans ). Seeds of C. calcarium are ellipsoid in outline, 7-7.5 × 3-3.5 mm, surface rugose to ± muricate (vs. seeds globose, 5-6.5 mm in diameter, surface strongly rugose in C. rutilans ).

Type.

Madagascar. Antsiranana: Diana, Ankarana Special Reserve, Tsingy Rary , 12°56'24.00"S, 49°07'04"E, 97 m, 16 May 2013, Rakotovao C. et al. 6376 (holotype: TAN!) .

Description.

Succulent erect shrub, up to 2 m tall. Old stems swollen, succulent; bark smooth, lenticellate; branches brown to reddish, shortly pubescent. Tendrils absent. Stipules triangular to ± falcate, 4-5 × 1.5-2.5 mm, soon caducous. Leaves 3-foliolate, central leaflet often drooping, somewhat thick and fleshy when fresh, becoming coriaceous when dry, usually folded upwards along the midrib; leaflets 3-5 × 1.5-2.5 cm, broadly oblong or elliptic, base cuneate, rounded to obtuse at the apex, margin shallowly denticulate; minutely puberulous and shiny on the adaxial surface, abaxial surface densely whitish pubescent to velvety particularly on the veins; venation closely reticulate, prominent. Petioles 1.5-2.5 cm long. Petiolules equal, up to 1 cm long. Inflorescence a compound dichasium, terminal, ca. 7.5 cm long, very shortly pubescent; bracts inconspicuous; pedicels 2-4 mm. Floral buds ± 2.5 mm long, minutely puberulous or glabrescent; sepals ± 0.5 mm long; petals reddish; stamens 4, filaments cylindrical, ca. 2.2 mm long, anthers ca. 0.8 mm long; ovary glabrous, styles ± 2.5 mm long. Fruits ellipsoid, 9-12 × 5-7 mm, glabrous. Seeds broadly ellipsoid, 7-7.5 × 3-3.5 mm, rugose; base rostrate; beak conspicuous; apex revolute; rugae apex shallowly conspicuous on both surfaces; chalaza linear, sinuate, up to 6 mm long (ca. 6/7 of seed length); ventral ridge raised, elongate but widened in the middle, extending up to 6/7 of seed length; endosperm m-shaped in cross-section.

Phenology.

Flowering and fruiting around May.

Etymology.

The epithet of the species refers to the habitats on limestone outcrops.

Distribution and habitat.

It grows on limestone outcrops in northern Madagascar at an altitude of 90-300 m. (Fig. 1 )

Provisional conservation assessment.

The new species is endemic to Madagascar with distribution restricted to its type locality. It is assessed here as Critically Endangered (CR) according to the IUCN Categories and Criteria ( IUCN 2019). Even though the species occurs within a protected area, succulent plants are still highly sought after by collectors for their horticultural values. Seeds of Cyphostemma calcarium should therefore be collected, banked, and propagated to ensure its long-term conservation.

Taxonomic notes.

This species is described from materials collected by Rakotovao C. et al. in 2013. It was initially identified as Cissus pileata Desc., but it clearly belongs to Cyphostemma in having constricted flower buds and floral disks with four free glands. These characters, together with its M-shaped endosperm as viewed in cross sections of the seeds and the presence of extra layers of endotestal sclereids covering the ventral infolds in cross-section, clearly distinguish the new species from Cissus L. A summary of some diagnostic characters that differentiate this new species from other shrubby species of Cyphostemma in Ankarana Special Reserve is provided in Table 1 .

Figures

Figure 1. Distribution map of Cyphostemma calcarium sp. nov. with the black dot showing the locality of the type specimens. Map on the right shows the position of Ankarana Special Reserve in Madagascar.

Figure 2. Comparison of two shrubby Cyphostemma species with 3 - foliolate leaves in the Ankarana Special Reserve A-E Cyphostemma calcarium sp. nov. A branches showing puberulent leaves and infructescence B-E seed morphology from Rakotovao C. et al. 6376 (Dorsal, ventral, lateral, and cross-section presented from left to right) F-J Cyphostemma rutilans Desc. F branches with glabrous leaves and inflorescence G-J seed morphology from Bardot-Vaucoulon M. 817 (Dorsal, ventral, lateral, and cross-section presented from left to right). Photos by Rakotovao Charles, Missouri Botanical Garden (A); Billiet Frieda, Meise Botanic Garden (F). The red arrow indicates an extra layer of endotestal sclereids covering the ventral infolds. Scale bars: 1 mm

Figure 3. Cyphostemma calcarium sp. nov. A branches showing the inflorescence and infructescence and the bark with distinct lenticels B trichomes on the abaxial leaflet surface C flower bud constricted at the middle D flower with petals and stamens removed to show the floral disc of 4 - large free glands E fruit with a persistent stigma (Illustration by Ai-Li Li; based on Rakotovao C. et al. 6376, TAN).