Octolepis ibityensis Z.S.Rogers, 2005

Rogers, Zachary S., 2005, A revision of Octolepis Oliv. (Thymelaeaceae, Octolepidoideae), Adansonia (3) 27 (1), pp. 89-111 : 104-107

4. Octolepis ibityensis Z.S.Rogers , sp. nov.

Haec species a Octolepide dioica, cui aliter similis est, foliis angustioribus 0. 8-1. 4 (haud 1. 4-4.0) cm latis, inflorescentiis unifloris (haud 3- ad 7-floris), pedicellis minus quam 2 (haud plus quam 4) mm longis et fructu 1. 4-1. 6 cm longo lineis dehiscentiae 1 vel 2 (haud 1. 9- 3 cm longo lineis (4 ad 5)) differt.

TYPUS. — Randrianaivo, Ranaivojaona, Birkinshaw, Ravololonanahary, Ralimanana & Randrianasolo 8, Madagascar, Prov. Antananarivo, Mont Ibity, à 2- 3 km à l’Est de la Cimenterie d’Ibity, 1590-1830 m, 20°04’40”S, 47°00’10”E, 19-21 Oct. 1993, ³ fl. (holo-, MO!; iso-, G!, P, TAN!, WAG!) .

Trees to 3 m tall; young stems sparsely moderately to sparsely strigose-tomentose or glabrescent. Leaves alternate to subopposite, rarely opposite; blades narrowly obovate or elliptic, c. 2.6-4.6 × 0.8-1.4 cm, length/width ratio c. 3- 5:1, coriaceous, surfaces discolorous, adaxial surface glabrescent, abaxial surface lighter green, sparsely strigose or glabrescent, apex emarginate, usually with a small notch, rarely rounded, margin sparsely strigose or glabrescent, revolute, more so near base, base short attenuate or cuneate; midrib sparsely strigose or glabrescent; venation strongly raised on both surfaces, secondary veins c. 6-7 pairs, ± parallel, straight or arched toward apex, angle of divergence from midrib 30-55°, submarginal vein loop c. 1-2 mm from margin; petioles 3-5 mm long, c. 1 mm in diam., strigose-tomentose or glabrescent. Inflorescences axillary, borne on the defoliated portion of the stem; fascicles 1-flowered; pedicels c. 1-2 mm long, c. 1 mm in diam., glabrescent or sparsely strigose. Flower buds 2.0-2.5 × 2. 0- 2.5 mm, sparsely strigose, ± smooth. Flowers 4- 6 mm wide; sepals 5, rarely 6, ovate, c. 2.5-3.5 × 2. 0-2.5 mm, coriaceous, strigose-tomentose or glabrescent on both surfaces, ± smooth, apex acute or rounded, margin tomentose; petals 5, rarely 6, moderately to sparsely pubescent on both surfaces; each petal lobe narrowly triangular, 2.1-3.2 × 0.4-0.5 mm, length/width ratio c. 5- 8:1, coriaceous, apex acute. Staminate flowers with 10 stamens, rarely 12; filaments 1.6-2.0 × 0.2-0.3 mm; anthers 0.5-0.8 × 0.4-0.6 mm; pistillode minute, obscured by dense erect receptacle trichomes, trichomes c. 0.5-0.8 mm long. Pistillate flowers (description based on persistent organs in fruit) with 10 staminodes, rarely 12; staminodes 0.8-1.2 mm long, 0.2-0.4 mm wide (at base), ± smooth, glabrous; rudimentary anthers globose; ovary surrounded by many erect receptacle trichomes, trichomes c. 0.5-0.8 mm long. Fruits ovoid or ovoid-pyramidal (with 3 faces), 1.4-1.6 × 1.2-1.4 cm; dehiscence lines 1 or 2, rarely 3 (i.e. 1-3 carpels develop), depressed, not bicarinate; pericarp fleshy, c. 2-3 mm thick, rugose or rugulose, sparsely strigose to nearly glabrous, trichomes of different lengths, trichomes 0.7-1.0 mm long or 0.1-0.2 mm long; persistent style to 1 mm long. Seeds dark brown

1 cm

or black, 1.1-1.2 cm long, 5-6 mm wide, sparsely puberulent, more evident near the poles. — Fig. 5.

DISTRIBUTION AND PHENOLOGY. — Octolepis ibityensis grows in narrow tracts of gallery forest along two ravines on the Ibity Massif in central Madagascar from 1450 to 1830 m elevation ( Fig. 8). The species flowers from October to January and fruits in January.

VERNACULAR NAME. — None available.

CONSERVATION STATUS. — Octolepis ibityensis is known from two remnant gallery forests on the slopes of the unprotected Ibity Massif. The lower slopes of the mountain are burned annually by local villagers, leaving only narrow (c. 5-15 m wide) tracts of forests running along streams that function as natural firebreaks and provide enough shelter to protect the small populations of O. ibityensis growing along them. However, due to the frequent burning, the tracts continue to narrow, and plants untouched by fire in 2003, have since been damaged to the point that they may not recover. Octolepis ibityensis is given the provisional status of Critically Endangered (CE B1ab+B2ab).

Octolepis ibityensis is distinguished from O. dioica , the most morphologically similar species, by its narrowly elliptic leaf blades, its shorter pedicels, its fewer flowered inflorescences, its smaller flowers (with shorter sepals, smaller petal lobes, shorter filaments, and smaller anthers), and its smaller fruits with fewer lines of dehiscence. Table 2 summarizes morphological differences between both species.

PARATYPES. — MADAGASCAR: Prov. Antananarivo: Rogers et al. 78, Ibity massif, c. 2-3 km E of the Ibity cement factory, along mountain stream of Be- Apombo , 1540 m, 20°04’14”S, 47°00’11”E, 20 Jan. 2003, st. (MO!); Rogers et al. 79, same general locality, along mountain stream of Falirano , 1470 m, 20°04’24”S, 47°00’10”E, 20 Jan. 2003, ³ y.fl. (MO!); Rogers et al. 80, same locality, fr. (MO!, P!, TAN!); Rogers et al. 81, same locality, st. (MO!); Rogers et al. 306, same locality, 28 Apr. 2004, st. (MO!) .

5. Octolepis oblanceolata (Capuron) Z.S.Rogers , comb. et stat. nov.

Octolepis dioica Capuron f. oblanceolata Capuron, Adansonia , n.s. 3: 140 (1963). — Type: Réserves Naturelles (Rakotoson) 10459, Madagascar, Prov. Toliara, Marovato, District : Amboasary , [24°41’S, 46°45 ’E], 16 June 1960, ³ fl. (lecto-, P- 00077575!, here designated; iso-, P[2]!, TEF!).

Trees to 10 m tall; young stems moderately to sparsely strigose-tomentose or glabrescent. Leaves alternate to opposite; blades broadly to narrowly obovate, rarely broadly elliptic, c. 6.5-12.4 × 1.3- 4.0 cm, length/width ratio c. 2-6:1, coriaceous, surfaces discolorous, adaxial surface glabrous, abaxial surface lighter green-brown, sparsely strigose or glabrescent, apex usually acute, sometimes emarginate or short cuspidate, margin sparsely strigose or glabrescent, revolute, undulate, base attenuate or cuneate; midrib strigose or glabrescent; venation raised to nearly inconspicuous on both surfaces, secondary veins c. 8- 12 pairs, ± parallel, arched toward apex in upper half of leaf, angle of divergence from midrib 35- 55°, submarginal vein loop c. 2-3 mm from margin; petioles 4-8(-9) mm long, c. 1.0- 1.5 mm in diam., glabrescent or sparsely strigose. Inflorescences axillary, usually borne on foliated portion of the stem; fascicles 2-flowered, usually 1 flower persistent; pedicels (0.9-) 1.1-1.5 cm long, 0.5-0.7 mm in diam., glabrescent or rarely sparsely strigose. Flower buds 3.5-4 × 3.5-4 mm, glabrescent, ± smooth. Flowers 1.1-1.3 cm wide; sepals 4 or 5, ovate or oblong, rarely subtriangular, 5-6(-8) × 2-3(-4) mm, coriaceous, glabrescent, rarely sparsely strigose on both surfaces, apex acute or rounded, tomentose, margins glabrescent or tomentose; petals 5, rarely 6, densely to sparsely strigose on both surfaces; each petal lobe narrowly triangular, 3.8-5.2 × 0.8-1.1 mm, length/width ratio 4-5:1, coriaceous, apex acute. Staminate flowers with 10 stamens, rarely 12; filaments c. 3.5-4.5 × 0.3-0.4 mm; anthers c. 2 × 1 mm long; pistillode minute, obscured by dense erect receptacle trichomes, trichomes c. 1 mm long. Pistillate flowers (description based on persistent organs in fruit) with 10 (12) staminodes; staminodes 1.3-1.9 mm long, 0.3-0.4 mm wide (at base), smooth; rudimentary anther globose; ovary surrounded by many erect receptacle trichomes, trichomes c. 2 mm long. Fruits subs p h e ro i d a l o r ovo i d -p y r a m i d a l, 1.7-2.1 × 1.7-2.4 cm; dehiscence lines 4 or 5 (i.e. 4 or 5 carpels develop), ± bicarinate on both sides of line; pericarp fleshy, 4-5 mm thick, rugulose or nearly smooth, sparse or moderately pubescent, trichomes c. 1-2 mm long, erect or subadpressed, ± rigid, not stinging; persistent style to 4 mm long. Seeds dark brown, 1.1-1.3 cm long, 5- 6 mm wide, puberulent, indument denser near poles.

Refer to CAPURON (1963: 139, pl. 2, No. 12) for an illustration of O. oblanceolata .

DISTRIBUTION AND PHENOLOGY. — Octolepis oblanceolata occurs in southeastern Madagascar near Fort-Dauphin from c. 400-700 m elevation (Fi g. 7). T h e s p e c i e s h a s b e e n c o l l e c t e d i n Andohahela National Park and was also found in 2003 growing on the forested slopes above St Jacques, a small village overlooking Fort- Dauphin. Since then, however, the population at St Jacques has been extirpated (J. RABENANTO- ANDRO pers. comm.). The species flowers in June to November and fruits from August to January.

VERNACULAR NAME. — Tsilorano (Réserves Naturelles 10072).

CONSERVATION STATUS. — Octolepis oblanceolata is known from three or four populations, perhaps only one of which is formally protected within the boundaries of Andohahela National Park (Parcel 1). The population above St Jacques discovered in 2002 has recently been lost. Locality data for the other collections are incomplete, making it difficult to calculate extent of occurrence and area of occupancy. The species is assigned a preliminary conservation status of Endangered (EN B1ab+B2ab).

TYPIFICATION. — Three sheets of the type collection (Réserves Naturelles 10459) are deposited at P. Each of the specimens was identified as type of Octolepis dioica f. oblanceolata by CAPURON. The sheet, bearing the accession number P-00077575, was annotated as the “Type de la forme”, the second (P-00077576) bears an isotype label affixed to the lower half of CAPURON’ s annotation slip, and the third is marked “Isotype d. l. [= de la] forme”. The style of the labels, the handwriting, and the completeness of the label information differs between all three sheets, but none of the data on the labels contradicts the protologue. Sheet (P-00077575) is the only sheet without the isotype designation and is selected as the lectotype.

Octolepis oblanceolata was originally considered to be a form of O. dioica by CAPURON (1963). The species is distinguished from O. dioica by its larger, oblanceolate or more broadly obovate leaves, its more strongly arched secondary veins in the upper half of the leaves, its more often acute apices, its undulate leaf margins, its longer pedicels ((9.0-) 11.0-15.0 vs 4.0-10.0(-14.0) mm long), and its larger flowers (11-13 vs 8-11 mm wide).

Four collections are excluded from Octolepis oblanceolata as circumscribed above. Three of them (A. Randrianasolo 790, Ludovic 721 and 734) have been made recently at Mahabo forest, a littoral forest fragment along Madagascar’s southeast coast, and appear to be the first ever collected on sand in Madagascar ( Octolepis casearia is frequently collected on sand in continental Africa). The fourth collection, Service Forestier 25524, was made in 1965 with an incomplete locality on the label, although it was probably made somewhere to the south of Mantadia National Park. There is also a good possibility that the collection was made near the coast, because it shares morphological similarities with the Mahabo specimens. All four collections have leaves that are clearly larger than those of O. dioica , resembling some of the broadly oblanceolate leaves found on p l a n t s o f O. o b l a n c e o l a t a. Howe ve r, t h e s e excluded specimens differ in having densely sericeous pedicels, and their smaller, much more densely pubescent fruits with 3, or rarely 4, dehiscence lines.

ADDITIONAL MATERIAL EXAMINED. — MADAGAS- CAR: Prov. Toliara: Randriamampionona 1308, Andohahela National Park , Emalio , Andranolava , Site de suivi éco-tourisme, [24°41’S, 46°45’E], 25 Aug. 1996, fr. (MO!, P, TAN!); Réserves Naturelles (Rakotoson) 10072, Canton Behara, district Amboasary, [24°41’S, 46°45’E], 5 Nov. 1958, ³ fl. (P!, TEF!); Randrianaivo et al. 880, Fivondronona Fort-Dauphin, Commune (Fokontany) Ampasinampoa, Forêt de Ambatomitikitra, à 3 km W du village St Jacques, forêt humide de basse altitude, 400-700 m, 24°58’56”S, 46°57’30”E, 2 Dec. 2002, fr. (MO!, P, TAN!); Rogers et al. 101, same locality, 520-660 m, 24°58’57”S, 46°57’24”E, 25 Jan. 2003, st. (MO!); Rogers et al. 102, same locality, fr. (MO!, P!, TAN!); Rogers et al. 103, same locality, fr. (MO!) .

Figures

FIG. 5. — Octolepis ibityensis Z.S.Rogers, sp. nov.: A, habit; B, staminate flower; C, relationship between sepals, bifid petals, and stamens; D, fruit. A, D, Rogers et al. 80 (TAN); B, C, Randrianaivo et al. 8 (TAN, type).