Oxandra unibracteata J.C.Lopes, Junikka & Mello-Silva, 2013

Lopes, Jenifer De Carvalho, Junikka, Leo & Mello-Silva, Renato, 2013, Oxandra unibracteata (Annonaceae), a new species from the Atlantic Forest and a new synonym of O. nitida, Phytotaxa 84 (1), pp. 25-30 : 25-28

Oxandra unibracteata J.C.Lopes, Junikka & Mello-Silva , sp. nov. ( Fig. 1–2 )

Oxandra unibracteata is similar to O. reticulata , but O. reticulata has elliptic to narrowly ovate leaves with a cordate base, pedicels 3–6 (–7) mm long, with 2–10 bracts and stipe of monocarps 1–3 (–4) mm long, whereas O. unibracteata has narrowly elliptic leaves with an acute to slightly attenuate base, 12–15 mm long pedicels with a single bract and stipe of monocarps 7–8 mm long.

Type:— BRAZIL. Espírito Santo: Linhares, Reserva Natural Vale, Estrada Flamengo km 11, 30 Nov 1981 (fl), Silva 272 (Holotype SPF!, isotypes CVRD!, RB!) .

Tree up to 25 m high; branchlets, petioles and buds glabrous; young branchlets with lenticels and two basal prophylls, deciduous, the proximal 2.5 mm long, the distal 1.5 mm long. Axillary buds with hairs or glabrous. Leaves coriaceous, glabrous, shiny above, verruculose mostly beneath, with black dots mostly on primary vein and with translucent dots in sicco; petiole 3.0–5.0 mm long; lamina 3.5–8.0 × 1.0– 2.5 cm, narrowly elliptic, apex acute to slightly acuminate, base acute to slightly attenuate; venation brochidodromous, primary vein raised, rarely impressed above, raised but not prominent below, secondary and tertiary veins raised or flat above, raised below, secondary veins 8–10 on either side, tertiary veins distinctly reticulate, angles between primary and secondary veins 45–70°. Inflorescence axillary, singleflowered; bract 1, 0.9–1.1 mm long, above basal articulation, ovate, margin ciliate. Flower pedicels 12.0–14.0 mm, glabrous, fruiting pedicel 14.0–15.0 mm long; flower buds globose; sepals ca. 2.0 × 2.3 mm, connate up to half its length, apex triangular, glabrous; outer petals 4.5 × 3.5 mm, free, imbricate, suborbiculate, glabrous, margins ciliate; inner petals 5.0 × 3.0 mm, narrowly elliptic, glabrous; stamens ca. 18, 2.0 mm long, curved, connective apex truncate, without a defined shape; carpels ca. 5, 1.2 mm long, ovule 1, basal, 0.4 mm long, ellipsoid. Fruit with persistent sepals, torus 2.5–3.5 mm in diameter with 1–5 monocarps 17.0–18.0 × 12.0–13.0 mm, ellipsoid, green to red in vivo, stipe 7.0–8.0 mm long, 0.4–0.5 × length of the monocarp; no conspicuous apicula. Fruit wall fleshy; longitudinal ribs and few obscure transverse grooves on the dried monocarp. Seeds 10.0–11.0 mm in diameter, ellipsoid, circular in transverse section. Seeds with crustaceous seed wall, raphe visible as fine rib, ruminations lamellate, endosperm glass-like.

Distribution and Phenology:— Oxandra unibracteata is endemic to the Natural Reserve Vale, in Espírito Santo, Brazil, where it grows in a fragment of the Atlantic Forest, at an elevation less than 100 m (28 and 65 m, Fig. 2 ). It flowers in November and fruits in May.

Etymology:— The species is named after the single bract on its pedicel, which is unique in the genus.

Vernacular name: — imbiú-preto.

Additional specimen examined (paratype):— BRAZIL. Espírito Santo: Linhares, Reserva Natural Vale, Estrada Ipê Amarelo , elev. 80 m, 10 May 1985 (fr), Folli 545 ( CVRD!, MO, RB!, SPF!, U) .

Oxandra is a Neotropical genus of Annonaceae with about 30 species ( Maas et al. 2011) mainly from the Amazon region, with four species from the Brazilian Atlantic Forest, including O. unibracteata ( Maas et al. 2002, 2012). The rarity of this species may be a result of difficulty in collecting trees up to 25 m tall. The other species from the Brazilian Atlantic Forest are Oxandra martiana ( Schlechtendal 1834: 326) R.E. Fries (1931: 165) , O. nitida R.E. Fries (1931: 160) and Oxandra reticulata Maas (1986: 261) . Oxandra martiana occurs in Rio de Janeiro, Espírito Santo and Minas Gerais and O. nitida in Rio de Janeiro, Espírito Santo and Bahia ( Maas et al. 2012). Oxandra reticulata has been found in more northerly states, from Maranhão, Piauí, Pernambuco and Bahia to Minas Gerais, Goiás, Mato Grosso do Sul and Espírito Santo ( Maas et al. 1986, 2012, Fig. 2 ). Despite O. reticulata and O. unibracteata being found in Espírito Santo, they prefer different habitats. Oxandra unibracteata grows in the tabuleiro forest in northern Espírito Santo at low elevations, less than 100 m, whereas O. reticulata flourishes in southern Espírito Santo in montane Atlantic Forest at an elevation of 600 to 900 m.

There are some observations about elevational separation in species of Annonaceae in Espírito Santo. Certain species occur in the tabuleiro forest but not in the montane Atlantic Forest and vice versa. Good examples are Xylopia decorticans D.M.Johnson & Lobão (2007: 208) , Unonopsis sancte-teresae Maas & Westra (2007: 521) from the montane Atlantic Forest and Duguetia sooretamae Maas (1999: 486) and Unonopsis renatoi Maas & Westra (2007: 517) from the tabuleiro forest.

The presence of a single bract on a long pedicel is the main diagnostic feature of Oxandra unibracteata . Although bracts are usually easily detached, scars on the pedicel can be easily detected, and therefore we regard this character as distinctive. Oxandra unibracteata resembles O. reticulata in having reticulately veined leaves. However, O. reticulata has elliptic to narrowly ovate leaves with a rounded to cordate base, pedicels 3 to 6 mm long, with 2–10 bracts and stipe of the monocarps 1 to 4 mm long. Oxandra unibracteata has narrowly elliptic leaves with an acute to slightly attenuate base, pedicels 12 to 15 mm long with a single bract and stipe of the monocarps 7 to 8 mm long. Oxandra unibracteata can be distinguished from O. nitida and O. martiana , in addition to its single bract, by the non-reticulate or slightly reticulate leaves and pedicels, which are 2 to 3 mm long (table 1).

Figures

FIGURE 1. Oxandra unibracteata. A. Flowering branchlet. B. Fruiting branchlet. C. Leaf. D. Bud. E. Flower, three petals removed. F. Stamens, front and lateral views. A, C–F from Silva 272; B from Folli 545, drawn by Klei Sousa.

FIGURE 2. Distribution of the species of Oxandra from the Brazilian Atlantic Forest. Oxandra unibracteata (), O. reticulata (), Oxandra nitida () and O. martiana ().