Xerochlamys elliptica F.Gérard

Hong-Wa, Cynthia, 2009, Endemic families of Madagascar. XII. Resurrection and taxonomic revision of the genera Mediusella (Cavaco) Hutchinson and Xerochlamys Baker (Sarcolaenaceae), Adansonia (3) 31 (2), pp. 311-339 : 329-330

6. Xerochlamys elliptica F.Gérard

Comptes rendus de l’Association française pour l’Avancement des Sciences 1914 (sess. 43): 407 (1915). — Type: Madagascar, sur le quartz du mont Ibity , dans des bois à tapia du centre de l’île, [19°45’S, 47°15’E], 1400 m, VI.1912, fl., Perrier de la Bâthie 3009 (holo-, P! [ P00389117 ]; iso-, K [image seen]) .

ADDITIONAL MATERIAL EXAMINED. — Madagascar. Prov. Antananarivo, Ibity, 20°08’23”S, 46°58’44”E, 1385 m, 21 VI .2005 , Hong-Wa et al. 330 (MO, P, TAN). — 20°08’40”S, 46°58’53”E, 1426 m, Hong-Wa et al. 347 (MO, P, TAN). — Prov. Fianarantsoa, Ihadilanana , 20°26’17”S, 47°03’42”E, 1449 m, 22.VI .2005 , Hong- Wa et al. 349 (MO, P, TAN). — Itremo , 20°31’55”S, 46°24’28”E, 1617 m, 24.VI.2005, Hong-Wa et al. 356 (MO, P, TAN).

DESCRIPTION

Small trees; young and older twigs glabrous. Leaf blades dark green above, whitish beneath, elliptic, 2.6-4 × 1-2 cm, subcoriaceous, glabrous, base cuneate, margin plane, thickened, apex slightly emarginate, midrib green, flat to slightly raised above, raised beneath, secondary veins conspicuous, 8-10 per side, 3.5-5 mm apart, looping 0.8-2 mm from the margin; petiole 3-5 mm long, glabrous. Flowers often solitary or sometimes in inflorescences, axillary, with 2 flowers; peduncle 1-2.5 mm long, glabrous; pedicel absent to 0.5 mm long, glabrous. Involucre light brown, cupulate, 3-7 × 3-9 mm, glabrous, occasionally with sparse white trichomes, teeth 13-21, 1- 2 mm long; flowers 13-26 mm long at anthesis from apex of pedicel to apex of petals; sepals oblong, 7-9 × 3-6.5 mm long, deeply emarginate, exserted 2-6 mm beyond the involucre; petals white, rarely pinkish, oblong, 10-19 × 6.5-13 mm, exceeding the involucre by 7-12 mm; disc 2.5-4 mm tall; stamens 18-37, 8- 14.5 mm long; ovary ovoid, 3-4 mm high, style 7-12 mm long, basally pubescent, stigma 2 mm wide. Fruits globose, 4-9 × 4-9 mm, exceeding the accrescent involucre by 4-8 mm; seeds black, flattened-ellipsoid, 2-5 mm long, 1-10 per fruit.

PHENOLOGY

Flowering and fruiting in June.

VERNACULAR NAME

Kitoto.

HABITAT

Quartzite substrate in evergreen sclerophyllous Uapaca bojeri (tapia) woodland from 1300 to 1600 m in the subhumid bioclimatic zone.

DISTRIBUTION

Known from only five specimens collected at Ibity and the Itremo massif ( Fig. 4 ).

REMARKS

This species can be recognized by its glabrous, elliptic leaf blades that are dark green above and whitish beneath, its very prominent venation, and its often solitary white flowers enclosed within a cupulate involucre. All these characters distinguish it from X. bojeriana , which is characterized by pubescent, elliptic to occasionally ovate leaf blades, indistinct leaf venation, and pink flowers often grouped into inflorescences. Gérard (1915, 1919) described X. elliptica , initially known from only a single specimen (Perrier 3009), but Perrier de la Bâthie (1931) and Cavaco (1952a, b) considered it to represent nothing more than an individual of X. bojeriana that was vigorously resprouting. Additional material now shows, however, that the features distinguishing X. elliptica are constant between individuals, across habitats and through time. Field observations also show that X. elliptica differs from several broadly co-occurring congeners ( X. bojeriana , X. diospyroidea and X. itremoensis ) by its growth pattern and its white (vs. pink) flowers.

Xerochlamys elliptica differs from X. villosa by its small leaf blades that are <4 cm long (vs.> 4 cm in X. villosa ), elliptic (vs. ovate), and abaxially white (vs. dull green), and its cupulate (vs. urceolate) involucre that is often glabrous (vs. yellow tomentose) but sometimes bears white trichomes.

CONSERVATION STATUS

With an extent of occurrence of 2491 km 2, an area of occupancy of 36 km 2 and none of the four subpopulations growing in currently protected areas, Xerochlamys elliptica should be considered Endangered [EN B1ab(i,ii,iii,iv)+2ab(i,ii,iii,iv)].

Figures

FIG. 4. — Distributions of Xerochlamys elliptica F.Gérard (Å), X. diospyroidea (Baill.) Baker (▲), X. tampoketsensis F.Gérard (■) and X. villosa F.Gérard (●) mapped on the bioclimatic zones of Madagascar (after Cornet [1974], simplified by Schatz [2000]).