Octolepis ratovosonii Z.S.Rogers, 2005

Rogers, Zachary S., 2005, A revision of Octolepis Oliv. (Thymelaeaceae, Octolepidoideae), Adansonia (3) 27 (1), pp. 89-111 : 108-110

6. Octolepis ratovosonii Z.S.Rogers , sp. nov.

Haec species quoad speciebus aliis Octolepidis ab pedicellis 1.6-2.5 cm longis, petalis 10 (haud 5), staminibus vel staminodiis 20 (haud 10, raro 8 vel 12) et pericarpio indumento denso bistrato praedito strato exteriore trichomatibus urticantibus constante differt.

TYPUS. — Rogers, Rakotonasolo & Ravelonarivo 165, Madagascar, Prov. Antsiranana, Anjanaharibe-Sud Réserve Spéciale, c. 2 km NE of main road, along trail to Ranomafana thermal spring, 976 m, 14°45’05”S, 49°29’45”E, fr. (holo-, MO!; iso-, BR!, K!, P!, TAN!, WAG!) .

Trees to 9 m tall; young stems densely to sparsely strigose-tomentose. Leaves alternate to opposite; blades broadly elliptic or obovate, c. 6.6- 16.5 × 2.3-5.3 cm, length/width ratio c. 2.5-4:1, coriaceous, surfaces discolorous, dark green and glabrous adaxially, abaxial surface dries a distinctive light green, sparsely strigose or glabrescent, apex retuse or notched, margin sparsely strigose or glabrescent, flat or slightly undulate, strongly revolute, more so near base, base short attenuate or cuneate; midrib moderately strigose or nearly glabrous; venation raised on both surfaces, higher order venation raised or inconspicuous, secondary veins c. 7-11 pairs, angle of divergence from midrib 45-65°, submarginal vein loop c. 3- 6 mm from margin; petioles 8-16 mm long, 1-2 mm in diam., strigose-tomentose. Inflorescences axillary, borne on foliated or defoliated portion of stem, 1-flowered; pedicels (in fruit) 1.6-2.5 cm long, (1.5-)2.0-3.0 mm in diam., surface obscured by dense indument. Flower buds 5.1- 7.0 × 4. 0-6.1 mm, surface obscured by dense indument, rugose. Flowers (description based on staminate flower buds and persistent organs in fruit) with 4-6 sepals; sepals triangular or ovate, (0.8-)1.0-1.1 × 0.5-0.9 cm, very coriaceous, c. 2- 4 mm thick (in fruit), both surfaces obscured by dense indument, trichomes c. 0.3-0.4 mm long; petals 10, densely to moderately strigose; each petal lobe narrowly triangular, 2.4-3.1 × 0.4- 0.6 mm, length/width ratio c. 4-6:1, coriaceous, apex acute. Staminate flowers with 20 stamens. Pistillate flowers with 20 staminodes; staminodes 1.5-1.9 mm long, 0.3-0.4 mm wide (at base), ± smooth, glabrous; rudimentary anthers well developed, c. 1.0-1.1 × 0.3-0.4 mm; ovar y surrounded by many erect receptacle trichomes, trichomes c. 1.5- 2.5 mm long. Fruits ovoid-subspheroidal, 2.4-2.9 × 2.2-2.8 cm; dehiscence lines (4-)5 or 6 (i.e. 4-6 carpels develop), strongly depressed, bicarinate on both sides of line; pericarp fleshy, 7-8 mm thick, rugose and pitted, surface obscured by 2-layered indument, shorter layer dense, trichomes 0.2- 0.3 mm long, erect, soft, longer layer sparse, trichomes c. 1.5 mm long, erect, stiff, stinging (when fresh); persistent style 2-4 mm long. Seeds red-brown, 1.3-1.7 cm long, 7-9 mm wide, surface obscured by dense puberulent indument. — Fig. 6.

DISTRIBUTION AND PHENOLOGY. — Octolepis ratovosonii occurs in humid forests, from 800- 1250 m elevation ( Fig. 7 ). The species has been collected in flower bud in February and in fruit in February, July, and August.

VERNACULAR NAMES. — None available.

CONSERVATION STATUS. — Octolepis ratovosonii is known from three formally protected areas (Anjanaharibe-Sud RS, Manongarivo RS, Zahamena PN). The extent of occurrence of the species is c. 28000 km 2. Area of occupancy is c. 10000 km 2 based on a 50 km grid cell size (cell width/height, not area). Octolepis ratovosonii should be considered Near Threatened (NT).

Octolepis ratovosonii differs markedly from all other species in the genus by having 10 (vs 4-6) petals, 20 (vs 10, rarely 8 or 12) stamens and staminodes, and larger flowers (probably 3-4 times larger than other species based on the flower buds). Other distinguishing features include its densely pubescent, long and robust (c. 1.6-2.5 cm × 1.5- 3.0 mm) pedicels, its large, thickened, densely pubescent sepals, its thick, rugose, pericarp covered in by a two-layered indument, the longer of which is composed of stinging trichomes, and its densely puberulent seeds. Octolepis ratovosonii can be recognized vegetatively from the other Malagasy species by having the largest, thickest, leaves with the most revolute margins, and by the light green color of the blades after drying.

The epithet has been chosen in honor of Fidisoa RATOVOSON, a Malagasy botanist, who

1 cm 1 cm 1 cm 1 cm

FIG. 6. — Octolepis ratovosonii Z.S.Rogers , sp. nov.: A, habit; B, fruit capsule; C, capsule after dehiscence; D, densely puberulent seed. Rogers et al. 165 (TAN, type).

c o l l e c t e d t h e s p e c i e s o n t w o o c c a s i o n s a t Zahamena National Park, and whose contributions have greatly increased our knowledge of the flora in that region.

PARATYPES. — MADAGASCAR: Prov. Antsiranana: Razafimandimbison et al. 229, Anjananharibe- Sud Réserve Spéciale, au sud de campement à Mandritsarahely , 985 m, 14°46’S, 49°30’E, 10 July 1996, fr. (G!, MO!, TAN!); Rogers et al. 164, Anjanaharibe-Sud Réserve Spéciale , c. 2 km NE of main road, along trail to Ranomafana thermal spring, 976 m, 14°45’05”S, 49°29’45”E, 18 Feb. 2003, ♀ y.fl., fr. (MO!); Rogers et al. 166, same locality, ³ y.fl. (MO!); Wohlhauser et al. 350, Manongarivo Réserve Spéciale, Vallée de l’Ambahatra (cours supérieur), Bassin de l’Ambahatra (bras gauche, à l’ouest d’Andetryfotsy), 1200 m, 14°00’S, 48°26’E, 21 Nov. 2000, fr. (G!). — Prov. Toamasina: Ratovoson et al. 247, Zahamena National Park , Fivondronana Ambatondrazaka, Firaisana Antanandava, Ankosy, Ambarikely (3 km à l’Est d’Ankosy), 996-1250 m, 17°28’48”S, 48°49’33”E, 12 July 2000, y.fr. (MO!, P, TEF!); Ratovoson et al. 726, Zahamena National Park , 800- 850 m, 17°29’S, 48°43’E, 3 Aug. 2003, fr. (MO!, P, TEF!); Service Forestier (Razakamalala & Norbert) 34487, Ambodivoahangy, Fir. Antanandava, Fiv: Ambatodrazaka, [17°56’S, 48°26’E], 15 Sept. 1997, fr. (TEF!) .

Figures

FIG. 7. — Distribution map of Octolepis aymoniniana Z.S.Rogers (▲), O. oblanceolata (Capuron) Z.S.Rogers (■), and O. ratovosonii Z.S.Rogers (✚).