Swartzia aptera DC.

  • Family

    Fabaceae (Magnoliophyta)

  • Scientific Name

    Swartzia aptera DC.

  • Description

    Authors: Benjamin M. Torke and Vidal de Freitas Mansano

    Type: French Guiana. Distr. Cayenne: Cayenne, 1821? (fl), J. Martin s.n. (holotype: G; isotypes: BM, F, P, US).

    Description: Tree to ca. 15 m; trunk to ca. 20 cm in diameter; bark smooth, dark gray; young branchlets glabrous to sparsely minute-strigulose. Leaves imparipinnate, with a single pair of opposite (to subopposite) lateral leaflets, occasionally with the rachis and terminal leaflet abortive; stipules triangular to lanceolate, 0.2-1.1 mm x 0.1-0.2 mm, glabrous or minte-strigulose abaxially, often caducous; petioles naked, essentially terete, 5-20 mm, glabrous or nearly so, pulvinus 1.5-2.8 mm, glabrous to sparsely minute-strigulose; rachis naked, essentially terete, 3.8-16.5 cm, glabrous; stipels absent or relictual; petiolules 1.8-3.6 mm, glabrous to sparsely minute-strigulose; leaflet blades chartaceous, elliptic or ovate, 1.9-3.1 x as long as wide, 2.7-9.7 x 1-4.4 cm, glabrous, base rounded-obtuse to broadly acute, apex caudo-acuminate, acumen rounded or weakly retuse, 6-15 mm, midrib immersed or impressed above, raised below, higher order venation inconspicuous, immersed above, somewhat raised or immersed below, secondary veins ca. 8 on each side of midrib, ascending at 20-30°, curving distally and forming loose submarginal loops, with several included intersecondary and tertiatry veins more or less parallel to secondaries. Inflorescences simple racemes or the flowers solitary, borne in leaf axils or on defoliate portion of branchlets just below leaves, 1-several-flowered; axes 0.6-6 cm, glabrous to sparingly minute-strigulose; bracts triangular to spatulate, 0.5-1.3 x 0.3-0.6 mm, strigulose; pedicels more or less terete, somewhat dilated distally, 1.5-4 cm, glabrous or nearly so; bracteoles opposite to strongly subopposite, inserted in the distal third of pedicel, linear to subulate, 0.6-1.1 mm, glabrous or nearly so; flower buds green, globose, 7-11 x 6.8-10.5 mm, glabrous. Calyx dull light green, glabrous; segments 3-5, subequal, ovate to elliptic, recurved, ca. 7-11 x 3.8-8.5 mm. Petal yellow, glabrous; claw 4-6.5 mm; blade broadly ovate, the base more or less truncate, 13.8-20 x 14.9-22.5 mm. Androecium glabrous, the stamens dimorphic or essentially trimorphic, but with two main groups; stamens of the abaxial group 12-21, filaments light yellow, dorso-ventrally compressed, 16.5-26.3 mm, anthers elliptic in outline, 1.2-1.3 x 0.9-1.1 mm; stamens of the adaxial to central group ca. 450, the outermost distinctly longer than the others, but with some intergradation, filaments yellow, 2.5-14 mm, anthers elliptic in outline, 0.7-1.2 x 0.6-0.9 mm. Gynoecium glabrous; stipe arcuate, bulbous at base, 1.1-2.2 cm; ovary light green, narrowly arcuate-elliptic in outline, laterally compressed, 5.5-9.9 x 1-1.5 mm, locule glabrous, ovules ca. 5-6; style terminal, 2-4 mm; stigma punctiform. Fruits glabrous; stipe ca. 2.2 cm; body reddish-brown with light-tan lenticels, more or less elliptic in outline, somewhat compressed laterally, base and apex shortly acute, ca. 4.1-5.5 x 2.1-2.3 cm. Seeds usually 1, elliptic in outline, laterally compressed, ca. 3.4 x 2 cm; aril maturing pale yellow, elliptic in outline, ca. 1.5 x 1.2 cm, adaxial, covering less than quarter of seed, margin fimbriose.

    Common names: No common names have been recorded.

    Distribution: Middle and lower reaches of river drainages that empty into the Atlantic Ocean in Eastern French Guiana and the northern quarter of the Brazilian state of Amapá, at less than 200 m elevation and less than 150 km from the coast. The northeastern limit of the distribution appears to be the Mahury-Comte drainage in French Guiana. To the southeast, the species occurs at least as far as the Calçoene drainage in Amapá, but the Brazilian part of the range has been little collected. The majority of existing collections were gathered in the basin of the Oyapock (Oiapoque), which spans the boarder region of French Guiana and Brazil.

    Ecology: Swartzia aptera has been collected in well drained upland rainforest, as well as seasonally inundated forest and rocky banks along rivers. One collection (R. A. A. Oldeman 2471) was reportedly taken in savanna. On a fieldtrip to French Guiana in 2001, the present author encountered a single mature individual growing on top of a ridge near the Comte River. Nothing is known about the pollination or dispersal ecology of S. aptera.

    Phenology: Flowering and fruiting are concentrated during the dry season, particularly from July to October. One flowering collection was taken in January. Fruits are also known from February and May.

    Taxonomic notes: Swatzia aptera is a morphologically anomalous species of section Recurvae. The species' few-flowered, typically axillary inflorescences with a thin central axis lead Cowan (1968) to align it with the species that were included in section Possira by Torke and Mansano (2009), but its bracteolate pedicels and gyoecium with the stipe much longer than the ovary belie its true affinities with species of section Recurvae. In the molecular phylogenetic analyses of Torke & Schaal (2008), S. aptera was well supported as the sister taxon of S. hostmannii, another morphologically isolated species. These two species, along with S. oriximinaensis, which has not been sampled in molecular studies, differ from other members of the section in having more numerous stamens and more elongate gynoecia and in lacking stalked malphigian trichomes. Together they probably form a clade that is sister to the rest of the section. Swartzia aptera can be easily distinguished from S. hostmannii and S. oriximinaensis by its trifoliolate (versus unifoliolate) leaves.

    Uses: No uses have been recorded.

    Etymology: Candolle did not explain his choice of the specific epithet, but it presumably derives from Linneaus' order Aptera, an artificial grouping of wingless insects. In the present context, it likely refers to the unwinged leaf rachis of the species.

    Conservation status: Despite its fairly modest distribution, S. aptera is probably not currently threatened. Although the coastal zone of French Guaiana and Amapá has experienced significant deforestation, much of the area remains forested. The species likely occurs in several protected areas, including the Parc Naturel Régional De Guyane in French Guiana and the Parque Nacional Montanhas do Tumucumaque in Brazil.

  • Floras and Monographs

    Swartzia aptera DC.: [Article] Cowan, Richard S. 1967. Swartzia (Leguminosae, Caesalpinioideae Swartzieae). Fl. Neotrop. Monogr. 1: 3-228.