Buxus calcarea G.E. Schatz & Lowry, 2002

Schatz, George E. & Lowry Ii, Porter P., 2002, A synoptic revision of the genus Buxus L. (Buxaceae) in Madagascar and the Comoro Islands, Adansonia (3) 24 (2), pp. 179-196 : 183-191

2. Buxus calcarea G.E. Schatz & Lowry , sp. nov.

Buxus madagascarica subsp. xerophila H. Perrier, Fl. Madagascar 113: 4-5 (1952), nomen inval., non rite publ. sine Latin, pro parte “ fa. calcicola H. Perrier”; syn. nov.

Haec species lamina foliari plerumque supra medium latiore ad congeneros madagascarienses nonnullos accedit, sed ab eis foliis minoribus (minus quam 35 mm longis) rigidissimis venatione ut videtur carentibus juventute glaucis distinguitur.

TYPUS. — Service Forestier (Capuron) 11870 [= H. Humbert & R. Capuron 29315], Madagascar, Prov. Toliara, Sud-Ouest: bush (sur calcaire) sur les falaises des environs de Lavanono [falaise côtière nord-

Fig. 3. — Distributions of Buxus , mapped on the bioclimatic zones of Madagascar (after CORNET 1974; see SCHATZ 2000). B. angustifolia (), B. calcarea (❋), B. capuronii () , B. humbertii (✚), B. itremoensis () , B. macrocarpa (J), B. madagascarica (*), B. monticola (•), B. moratii (Δ).

ouest du Cap Sainte-Marie vers Lavanono], [25°28’S, 45°00’E], 1-150 m, 8 Mar. 1955, fr. (holo-, P!; iso-, K!, MO!, P!, TEF!) .

Shrubs to small trees to 4-5 m, young stems

1 mm diam., glaucous with short, erect tri- chomes, internodes 7-11 mm. Leaves very stiff and thick coriaceous, glaucous when young, 0.7- 3.2 × 0.3-1.1 cm, oblanceolate to obovate or sometimes narrowly elliptic, usually broader above the middle, apex rounded to obtuse or rarely acute, base cuneate to attenuate, midrib invisible above, evident and slightly raised towards the base below, secondary venation absent; petioles 1-2 mm long. Flowers solitary, axillary; male flowers subtended by 8-12, slightly keeled, minute bracts; sepals 4, 0.6-1 × 1-1.2 mm, broadly ovate, apex rounded; anthers 4, sessile, 1.5 × 1 mm; female flowers subtended by 8 slightly keeled, minute bracts; sepals 4, 1.2-1.6 × 0.9-1.8 mm, broadly ovate, keeled, apex obtuse to acute, styles 3, 3- 4 mm long, apex strongly recurved, stigma borne along inside of upper 2/3. Fruits 6-8.5 × 5 mm, ellipsoid, stylar remnants 2 mm; seeds 5.5 × 3 mm. — Fig. 4 .

Buxus calcarea is known from subarid deciduous thicket on tertiary limestone in southwestern Madagascar, from the Mahafaly plateau to Angavo east of Antanimora (Fig. 3). Among the species with leaf blades usually broader above the middle, B. calcarea can be distinguished from B. capuronii and B. humbertii by its small, very stiff coriaceous leaves lacking any visible venation, which are glaucous when young.

CONSERVATION STATUS. — Buxus calcarea is known from only 4 localities, and has not been collected since 1963. With an Extent of Occurrence of c. 3,650 km 2, an Area of Occupancy of perhaps only 400 km 2, and only 4 sub-populations, B. calcarea is assigned a preliminary status of Endangered (EN B1ab2ab).

PARATYPES. — MADAGASCAR, Prov. Toliara: Perrier de la Bâthie 5989, plateau Mahafaly (Menarandra), [24°42’S, 45°03’E], June 1910, fl. ( P, 2 sheets) ; Service Forestier (Capuron) 8485, Sud-Ouest: bush, à l’est du Mandrare, sur la route d’Ambovombe à Ft. Dauphin, [25°01’S, 45°30’E], 22 Sep. 1953, fl. ( P, TEF) ; Service Forestier (Capuron) 22484, Sud: crête du massif de l’Angavo à l’est d’Antanimora, [24°50’S, 45°48’E], 500 m, 23 Jan. 1963, fr. ( MO, P, TEF) .

3. Buxus capuronii G.E. Schatz & Lowry , sp. nov.

Haec species lamina foliari plerumque supra medium latiore ad congeneros madagascarienses nonnullos accedit, sed ab eis foliis majoribus (maximo plus quam 40 mm longo) supra secus costam rubellam trichomatibus albis erectis brevibus obtectis distinguitur.

TYPUS. — Service Forestier (Capuron) 24212, Madagascar, Prov. Mahajanga, Ouest (Ambongo): forêt de Tsiombikibo [FC], à l’ouest de Mitsinjo, [16°00’S, 45°44’E], 19 Nov. 1965, fl. (holo-, P!; iso-, BR!, C!, G!, K!, MO!, P (2)!, PRE!, TEF!, US!, WAG!) .

Small tree, stems 1 mm diam., reddish, prominently ridged, covered with sparse, short, erect, white trichomes, internodes 5-11 mm. Leaves coriaceous, 3-5.1 × 0.6-1.8 cm, narrowly obovate to obovate, apex rounded to obtuse, base cuneate to attenuate, midrib raised and rounded above, 0.2 mm broad at apex broadening to 0.9 mm broad at base, reddish, with short, erect, white trichomes becoming dense toward the base, slightly raised below, secondary veins 12-16 per side, barely visible on young leaves; petioles 1-2 mm long. Flowers axillary; male flowers solitary or 3 per axil, subtended by 8 or 12, slightly keeled, minute bracts; sepals 4, 0.8 × 0.6-0.9 mm, broadly ovate, the apex rounded to acute; anthers 4, sessile, 1.6- 1.7 × 0.7-0.8 mm; female flowers solitary, or 2-3 per axil, or the central flower in bisexual inflorescences, subtended by 12 strongly keeled, minute bracts; sepals 4, 1.5 × 1.6 mm, triangular, strongly keeled, the apex acute, styles 3, exserted only 0.5 mm above sepals. Fruits unknown. — Fig. 5 .

Buxus capuronii is known only from the type collection, gathered by CAPURON in November, 1965, at the dry deciduous forêt de Tsiombikibo to the west of Mitsinjo in the Ambongo region (Fig. 3). Among the species with leaf blades broader above the middle, B. capuronii can be distinguished from B. calcarea and B. humbertii by its larger leaves with the midrib above bearing short, erect, white trichomes.

ETYMOLOGY. — This species is named in honor of René CAPURON, who contributed so much to our knowledge of Madagascar’s woody flora.

CONSERVATION STATUS. — Because Buxus capuronii is known only from a single historical collection, the available data are insufficient to assess its conservation status. It must therefore be regarded as Data Deficient (DD). Tsiombikibo currently retains the status of a Forêt Classée, and thus there is hope that B. capuronii still persists there, or in nearby Baie de Baly PN.

4. Buxus humbertii G.E. Schatz & Lowry , sp. nov.

Buxus madagascarica subsp. xerophila H. Perrier, Fl. Madagascar 113: 4-5 (1952), nomen inval., non rite publ. sine Latin, pro parte “ fa. silicicola H. Perrier”; syn. nov.

H a e c s p e c i e s l a m i n a f o l i a r i p l e r u m q u e s u p r a medium latiore ad congeneros madagascarienses nonnullos accedit, sed ab eis foliis minoribus (minus quam 35 mm longis) glabris venatione secundaria tertiariaque supra manifesta apice plerumque emarginatis distinguitur.

TYPUS. — Humbert 13695, Madagascar, Prov. Toliara, bassin de réception de la Mananara, affluent du Mandrare, pentes occidentales des montagnes entre l’Andohahela et l’Elakelaka entre Ampahiso et Mahamavo (gneiss), vers 700 m, [24°45’S, 46°43’E], Jan.-Feb. 1934, fr. (holo-, P!; iso-, MO!, P!) .

Shrubs to small trees, young stems <1 mm diam., glabrous, internodes 4-9(-20) mm. Leaves coriaceous, glabrous, greenish and somewhat glossy, 0.8-2.2 × 0.3-1 cm, oblanceolate to obovate, slightly convex, apex rounded and often emarginate, base attenuate and decurrent, midrib flat to slightly impressed along lower half above, slightly raised below, dense secondary and tertiary venation evident and slightly raised above; leaves subsessile, petioles <1 mm long. Flowers unknown, axillary; sepals of female flowers in fruit 2 × 1.5-1.8 mm, triangular, the apex acute to obtuse. Fruits 6-7 × 4.5-5 mm, ellipsoid, the stylar remnants 1 mm long; seeds 3-3.5 × 2 mm. — Fig. 6 .

Buxus humbertii is known from three disjunct areas of dry to subarid deciduous thicket and forest in southern Madagascar, possibly associated with siliceous soils on gneiss (Fig. 3): the western slopes of Andohahela PN in the upper Mananara river basin; the Menarahaka river valley east of Ihosy; and Zombitsy PN near Sakaraha, where it was last collected in 1972. Among the species with leaf blades usually broader above the middle, B. humbertii can be distinguished from B. calcarea and B. capuronii by its small, somewhat convex leaves with distinct secondary and tertiary venation visible on the upper surface and with a usually emarginate apex.

ETYMOLOGY. — The species epithet honors Prof. Henri HUMBERT , who conducted extensive field work in Madagascar over five decades, and who contributed greatly to our understanding of the Malagasy flora and vegetation.

CONSERVATION STATUS. — Buxus humbertii is known from only 3 localities, and has an Area of Occupancy of approximately 300 km 2 within an Extent of Occurrence of c. 24,765 km 2. Thus, despite the fact that it may persist at two protected areas (Zombitsy PN and Andohahela PN), B. humbertii is assigned a preliminary status of Endangered (EN B2ab).

PARATYPES. — MADAGASCAR, Prov. Toliara: Debray 1913, forêt du Zombitsy-Sakaraha, [Zombitsy PN], [22°46’S, 44°42’30”E], 30 Nov. 1972, st. ( MO, P) ; Guillaumet 2438, forêt du Zombitsy-Sakaraha, [Zombitsy PN], [22°46’S, 44°42’30”E], Apr. 1969, st. ( P, TAN) ; Service Forestier (Capuron) 20229, Ouest : forêt du Zombitsy, à l’est de Sakaraha, [Zombitsy PN], [22°46’S, 44°42’30”E], 3-5 Apr. 1961, fr. ( K, MO, P, TEF) ; Service Forestier 96-R-10, forêt de Menarahaka, Dist. d’Ihosy, [22°32’S, 46°29’50”E], Dec. 1951, st. ( MO, P, TEF) ; Service Forestier 46-R- 239, Menarahaka, Ihosy, [22°32’S, 46°29’50”E], 7 Feb. 1954, st. ( P, TEF) ; Service Forestier 207-R-239, forêt de Menarahaka, Dist. d’Ihosy, [22°32’S, 46°29’50”E], 25 Mar. 1956, st. ( P, TEF) .

5. Buxus itremoensis G.E. Schatz & Lowry , sp. nov.

Haec species ab omnibus congeneris madagascariensibus foliis maturis linearibus distinguitur.

TYPUS. — Labat, Du Puy & Andriantiana 2441, Madagascar, Prov. Fianarantsoa, Ambatofinandrahana , Itremo, juste à l’est du col d’Itremo, 20°34’13”S, 46°35’08”E, 1560 m, 26 Nov. 1993, fl., fr. (holo-, P!; iso-, K!, MO!, TAN!, TEF!, WAG).

Rheophytic shrub 2 m tall growing amongst rocks in streambed, completely glabrous. Stems 0.6 mm diam, distinctly 4-angled, internodes 4-10 mm. Leaves coriaceous, 1.4-3.7 × 0.09-0.3 cm, linear, sometimes slightly falcate, apex acute to acuminate, base attenuate and decurrent along stem, midrib flat to slightly raised above, raised below, secondary venation absent; leaves subsessile, petioles to 0.4 mm. Flowers solitary, axillary, subtended by several minute bracts; male flowers with 4 minute sepals less than 0.5 mm long, anthers 4, sessile, fused at their base, 1 × 0.4 mm; female flowers with 4 minute sepals less than 0.5 mm long, styles 3, sessile, 3 mm long, the apex strongly recurved, stigma borne along inside of upper 2/3. Fruits 3-3.5 × 2-2.5 mm, ellipsoid, the stylar remnants 1.6 mm long. — Fig. 7 .

Buxus itremoensis is a rheophytic shrub known only from the Itremo massif (Fig. 3). It can be easily distinguished from all other Malagasy Buxus species by its linear, slightly falcate leaves. Both Buxus madagascarica and B. monticola also exhibit linear leaves during the juvenile seedling stage, as illustrated by PERRIER DE LA BÂTHIE (1952) in the Flore de Madagascar (undoubtedly based upon Perrier de la Bâthie 13275 for B. madagascarica ). Thus, Buxus itremoensis possi- bly represents a case of paedomorphism, with retention of juvenile leaves into the adult reproductive stage.

CONSERVATION STATUS. — With only a single sub-population outside the current protected areas network, an Extent of Occurrence less than 100 km 2 and an Area of Occupancy less than 10 km 2, B. itremoensis should be considered Critically Endangered (CR B1ab2ab). It joins numerous other plant species restricted to the Itremo massif, which is among the very highest priority areas for plant conservation in Madagascar.

PARATYPES. — MADAGASCAR, Prov. Fianarantsoa: Humbert 30033, montagnes à l’ouest d’Itremo, bois des pentes occidentales sur gneiss et quartzites, [20°34’S, 46°34’E], 1500-1700 m, 17-22 Jan. And 18-22 Apr. 1955, fr. ( CAS, G, K, MO, P (3 sheets), WAG) ; Lowry, Schatz, Andriamihajarivo, Hong-Wa, Rapanarivo & Rabarison 5822, Itremo massif, W of Ambatofinandrahana along road to Col d’Itremo, just below bridge over Ambalorangolana river , wet creek bed, 20°34’40’’S, 46°35’11’’E, 1540 m, 9 Nov. 2002, fl. ( CAS, G, K, MO, P, TEF, WAG) ; Randrianaivo, Birkinshaw, Rakotomamonjy, Andriatiana, Randrianasolo & Rasolomanana 154, Itremo, 20°34’S, 46°34’E, 1630-1770 m, 6 Apr. 1998, fr. ( MO, P, TAN) ; Schatz, Razafindrakoto, Andrianjafy & Rabenantoandro 3980, Itremo, 20°34’21”S, 46°34’54”E, 1580 m, 11 Mar. 2000, fr. ( MO, P, TEF) ; Service Forestier (Capuron) 11556, Mont Ambatomenaloha, W d’Itremo, restes de forêts dans les thelwegs humides, [20°34’S, 46°34’E], 18 Jan. 1955, fl. ( G, K, MO, P (2 sheets), TEF) ; Service Forestier (Capuron) 29041, berges et rochers encombrant le lit de l’Ambatorangotana dans le montée au col de l’Itremo, [20°34’S, 46°34’E], 1600 m, 21 Feb. 1970, fr. ( MO, P (2 sheets), TEF) ; van der Werff & McPherson 13585, massif d’Itremo, 20°37’S, 46°35’E, 1500 m, 27 Oct. 1994, fl., fr. ( MO, TAN) .

Figures

Fig. 4. — Buxus calcarea: A, fruiting branch; B, leaf, adaxial surface; C, leaf, abaxial surface. (Service Forestier 11870).

Fig. 5. — Buxus capuronii: A, flowering branch; B, leaf, adaxial surface; C, leaf, abaxial surface. (Service Forestier 24212).

Fig. 6. — Buxus humbertii: A, flowering branch; B, leaf, adaxial surface; C, leaf, abaxial surface. (Humbert 13695).

Fig. 7. — Buxus itremoensis: A, flowering and fruiting branch; B, leaf, adaxial surface; C, leaf, abaxial surface. (Labat et al. 2441).