Octolepis aymoniniana Z.S.Rogers, 2005

Rogers, Zachary S., 2005, A revision of Octolepis Oliv. (Thymelaeaceae, Octolepidoideae), Adansonia (3) 27 (1), pp. 89-111 : 94-97

1. Octolepis aymoniniana Z.S.Rogers , sp. nov.

Haec species a speciebus aliis Octolepidis lamina foliari tenui marginibus haud revolutis, venis secondariis numerosis (15 ad 25), pedicellis filamentosis 0.3 - 0.5 mm in diametro et trichomatibus numerosissimis 2.5-3 mm longis gynoecium cingentibus differt.

TYPUS. — Kotozafy & Randriamanantena 355, Madagascar, Prov. Fianarantsoa, Ranomafana Parc National (parcelle 1), à Antara, à 7 km au N de la ville d’Ambatolahy, c. 900 m, [21°14’S, 47°26’E], 19- 21 Oct. 1993, ♀ fl. (holo-, MO!; iso-, TAN!, WAG!) .

Treelets to 2 m tall; young stems densely strigose-tomentose. Leaves alternate to subopposite; blades broadly elliptic or elliptic-oblong, c. 6.1-9.7 × 1.7-2.5 cm, length/width ratio c. 3- 4:1, chartaceous, surfaces ± discolorous, adaxial surface glabrous, abaxial surface lighter green, sparsely strigose or glabrescent, apex attenuateacuminate (rarely subacute), acumen up to 9 mm long, margin sparsely strigose or glabrescent, slightly undulate, base short attenuate or cuneate; midrib strigose; venation raised on both surfaces, densely congested, secondary veins 15-25 pairs, closely-spaced, angle of divergence from midrib 50-65°, submarginal vein loop 1-2 mm from margin; intersecondaries nearly parallel, closely-spaced; petioles 5-7 mm long, c. 1 mm in diam., densely strigose-tomentose or glabrescent. Inflorescences axillary, borne on defoliated portion of stem; fascicles 1-4- flowered, 1 or 2 flowers persistent; pedicels c. 8-14 mm long, filamentous (0.3-0.5 mm in diam.), glabrous, base strigose. Flower buds 3-3.5 × 3 mm, sparsely strigose or glabrescent, surface smooth. Flowers 9-11 mm wide; sepals 5, ovate or oblong, 3.6-4.5 × 1.7-2.2 mm, coriaceous, sparsely strigose or glabrescent on both surfaces, apex acute, strigose-tomentose, margins tomentose or glabrescent; petals 5, densely strigose on both surfaces; petal lobes narrowly triangular, each lobe 3.7-4.3 × 0.5-0.7 mm, length/width ratio c. 6-7:1, coriaceous, apex acute. Staminate flowers not seen. Pistillate flowers with 10 staminodes, each 1-1.2 mm long, 0.1-0.2 mm wide (at base), rugulose, glabrous; rudimentary anthers globose; ovary 0.8-1.4 × 1.1-1.8 mm, surrounded by hundreds of erect receptacle trichomes, each 2.5-3 mm long; style 3.1-3.8 × 0.2-0.4 mm, glabrescent, base strigose. Fruits not seen. — Fig. 3.

DISTRIBUTION AND PHENOLOGY. — Octolepis aymoniniana , known only from the type collection, was made in dense, humid, primary forest within Ranomafana National Park at 900 m elevation ( Fig. 7 ). The species was collected in flower in October.

VERNACULAR NAMES. — None available.

CONSERVATION STATUS. — Octolepis aymoniniana is known from a single collection made in 1993. Despite a thorough search of the type

1 cm

locality accompanied by the original collector (KOTOZAFY), I was unable to locate other individuals in 2003. The site falls within the current boundaries of Ranomafana National Park. Vegetation at the locality remains in good condition, so it is likely that O. aymoniniana still occurs there. The species is assigned a provisional status of Vulnerable (VU B1ab+B2ab).

Octolepis aymoniniana is distinguished by the highly congested venation consisting of 15- 25 pairs of closely-spaced secondary veins with many intersecondaries, and the small, narrow, elongated areolae. The species differs markedly from other members of the genus by its filamentous pedicels (c. 0.3-0.5 mm in diam.) and by the hundreds of long receptacle trichomes (2.5-3 mm long) surrounding the gynoecium in pistillate flowers. Vegetatively, the species can be recognized from all other Malagasy Octolepis by the thin, chartaceous leaf blades with attenuateacuminate (or infrequently subacute) apices and non-revolute margins.

Octolepis aymoniniana is named in honor of Gérard-Guy AYMONIN, whose lifetime study of paleotropical Thymelaeaceae has been a great contribution to our knowledge of the family.

Figures

FIG. 3. — Octolepis aymoniniana Z.S. Rogers, sp. nov.: A, habit of pistillate individual; B, base of inflorescence and leaf scar; C, pistillate flower (note ovary surrounded by hundreds of long, erect, filamentous receptacle trichomes); D, relationship between sepals, bifid petals, and staminodes. Kotozafy & Randriamanantena 355 (TAN, type).

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