Olax antsiranensis, Rogers & Malécot & Sikes, 2006

Rogers, Zachary S., Malécot, Valéry & Sikes, Kendra G., 2006, A synoptic revision of Olax L. (Olacaceae) in Madagascar and the Comoro Islands, Adansonia (3) 28 (1), pp. 71-100 : 75-77

1. Olax antsiranensis

Z.S.Rogers, Malécot & Sikes, sp. nov. ( Fig. 1 )

“ Olax pseudaleioides subsp. sabulicola ” Capuron, Olacacées, Opiliacées et Santalacées arbustives ou arborescentes de Madagascar: 13 (1968), nomen inval. [ineffective publication].

Olax antsiranensis a O. thouarsii in laminis 1.5-4 (haud 5-12) cm longis (n.b.: bracteis interdum foliaceis!) plus minusve concoloribus et apicibus emarginatis (haud paginis abaxialibus glaucis et apicibus acutis acuminatis vel raro obtusis vel rotundatis), et ligulis petalorum 0-0.3 (haud 0.6-1) mm longis indumento pubescenti sparso (haud dense) praeditis, differt.

TYPUS. — Madagascar. Prov. Antsiranana, au Sud du Mont Raynaud, sur sables, [12°30’S, 49°27’E], 26.IV.1963, fl., Service Forestier (Capuron) 22719 (holo-, P!; iso-, P- 00418010!, TEF!) .

PARATYPES. — Madagascar. Prov. Antsiranana, souspréfecture de Vohémar, commune rurale de Daraina, forêt de Bekaraoka, partie sud Andranostimaty , 13°11’S, 49°42’E, 130 m, 10.III.2003, fl., Gautier et al. 4305 (G, INH!) . — Ramena, Andavakoera, à 8 km au Sud du village Andavakoera , forêt sèche sur sable, 12°20’53”S, 49°21’27”E, 50 m, 11.VIII.2004, imm. fr., Guittou et al. 75 (K!, MO!) . — Analabe forest, Fivondronana Vohémar, Fokontany Anjiabe , 13°04’14”S, 49°53’40”E, 26.II.2003, fl., Rabevohitra et al. 4554 (K!, MO!, P!, TEF). — Fivondronana Diego II, Commune Ramena, Fokontany Andavakoera, forêt sèche d’Andranonankomba, Montagne des Français , 12°20’48”S, 49°21’28”E, 88 m, 7.IX.2004, fr., Randrianaivo et al. 1074 (G!, MO!, P, TAN, TEF). — Same locality, 12°23’02”S, 49°20’12”E, 310 m, 28.III.2004, fl., Ratovoson et al. 735 (MO!, P, TAN) . — Tendrombohitr’Antsingy [= Montagne des Français], [12°22’S, 49°21’E], 26.XI.1958, fr., SF (Capuron) 20103 (P!, TEF!) . — Sakaramy STF, forêt d’Analandriana, près de Sakoramy ( Diégo-Suarez ), [12°26’S, 49°16’E], 17.XII.1963, fr., SF (Capuron) 23017 (P!, TEF!) . — Ambongoabo massif, à l’Ouest de Diégo-Suarez , [12°15’S, 49°10’E], 26.I.1966, fr., SF (Capuron) 24442 (P!, TEF!) . — Vohémar , [13°22’S, 50°00’E], 14.X.1966, fr., SF (Capuron) 24867 (P!, TEF!) .

DESCRIPTION

Trees to 10 m tall. Branches glabrous; young branches 4-sided, winged; older branches terete, darker; bark cracked, exfoliating. Leaves alternate, distichous, elliptic or ovate, rarely obovate, 1.5- 4 cm long, 9-23 mm wide, c. 2-2.5 times longer than wide; leaf blades chartaceous, glabrous, surfaces smooth, rarely slightly wrinkled, usually darker in color adaxially, base acute-cuneate (decurrent with petiole), margin slightly revolute, more obvious in lower half, apex apparently emarginate, sometimes with a short mucron in the sinus; midrib depressed or slightly raised adaxially, raised abaxially, glabrous; venation usually conspicuous on both surfaces, less pronounced abaxially, secondary veins c. 5 pairs per side; petioles 0-0.5 mm long, c. 1 mm in diam., glabrous. Inflorescences racemose or pseudosolitary; axes 4-sided, c. 0.5 mm in diam., reaching 7 mm long, proliferating with up to 5 flowers; floral pedicel 2.2-2.8 mm long, c. 0.5 mm in diam. Flowers hermaphroditic, tubular, heterostylous; calyx cupuliform, green, 1-1.2 mm long, semimembranous, glabrous, margin truncate; petals 5, white, oblong, 5.8-7.7 mm long, glabrous adaxially; petal lobes c. 3 mm long, 1.1-1.7 mm wide; petal ligule absent or up to 0.3 mm long, sparsely puberulent or glabrous; free portion of filaments 1-2 mm long; fertile stamens (5) 6 (7); anthers oblong, c. 1.5 × 0.7 mm, longitudinally dehiscent; staminodes 4 or 5, each bifid portion narrowly elliptic, c. 2 × 0.5 mm, membranous, glabrous, base thick, dark, articulate with filament; nectary disc annular, 0.1-0.2(-0.3) mm tall, glabrous; ovary ovoid-spheroid, c. 1.2 × 1 mm; style c. 0.4 mm in diam., articulate above ovary in immature fruit; long style not seen; short style 2.3-2.7 mm long; stigma capitate, 3-lobed, 0.4- 0.6 mm in diam., papillate. Drupes transversely ellipsoid, uniformly depressed at both poles, 1.1-1.2 cm long, 1.5-1.7 cm in diam., yellow, glabrous; accrescent calyx surrounding base of fruit, thin and chartaceous, 7-8 mm in diam., margin tearing irregularly into 4-8 lobes; stylar remnants c. 0.2 mm long.

REMARKS

The flowers of Olax antsiranensis have 5 petals, (5) 6 (7) stamens, 4 or 5 staminodes, and a weakly accrescent calyx in fruit. Olax antsiranensis is distinguished from O. thouarsii by its 1.5-4 (vs. 5- 12) cm long leaves, the more or less concolorous leaf blade with an emarginate apex (vs. abaxially glaucous blade with an acute, acuminate, or rarely obtuse or rounded apex), and by the 0-0.3 (vs. 0.6-1) mm long, sparsely (vs. densely) pubescent petal ligule. Please note that leaves of O. thouarsii should not be confused with its foliose bracts (see species no. 8 for further discussion).

The placement of this taxon was not addressed in the Flore ( Cavaco & Keraudren 1955a) because no collections were available at that time. Capuron (1968) collected Olax antsiranensis on five occasions, considering it to be a subspecies of O. thouarsii (though he regarded O. pseudaleioides to be the correct name for the species). We believe that O. antsiranensis deserves recognition at the rank of species.

DISTRIBUTION AND PHENOLOGY

Olax antsiranensis occurs in a few dry forest fragments in northern Madagascar near Diégo-Suarez and Vohémar from 0 to 310 m elevation (Fig. 11). The species grows on sand, calcareous limestone, and lateritic soil on basaltic rock. It flowers February through April and fruits from August to January.

VERNACULAR NAME

Kombimba (Ratovoson et al. 735); Sarinkombimba (Guittou et al. 75).

USE

“Fakaboka” (Ratovoson et al. 735). In Malagasy, Fakaboka means the plant is used by sorcerers to curse people (F. Ratovoson pers. comm.).

CONSERVATION STATUS

Olax antsiranensis grows in one protected area (Sakaramy). The EOO of the species is 1400 km 2, a figure which easily meets the requirements of B 1 in the EN category (i.e. EOO <5000 km 2). AOO for the species is 600 km 2 (grid cell size 10 × 10 km) and does not quite qualify as EN in the B2 category (i.e. AOO <500 km 2). Therefore, the spe- cies is assigned a provisional conservation status of Vulnerable (VU B1ab + 2ab).

Figures

FIG. 1. — Olax antsiranensis Z.S.Rogers, Malécot & Sikes: A, flowering branch; B, flower (two petals, two stamens and two staminodes removed); C, fruit. A, Service Forestier 22719 (type); B, Rabevohitra 4554; C, Service Forestier 20103. Scale bars: A, 1 cm; B, 3 mm; C, 4 mm.