Swartzia discocarpa Ducke

  • Family

    Fabaceae (Magnoliophyta)

  • Scientific Name

    Swartzia discocarpa Ducke

  • Description

    Authors: Benjamin M. Torke and Vidal de Freitas Mansano

    Type: Brazil, Pará, rapids of Mangabal, middle Tapajós River, 9 Feb 1917 (fl), A. Ducke s.n., RB Herb. No. 17067 (lectotype, designated by R. S. Cowan, Fl. Neotrop. Monogr. 1: 122. 1968: S; isolectotypes: G, K, P, RB, U, US).

    Description: Tree to 15 m+; trunk to 50 cm+ in diameter; young branchlets thinly to moderately strigulose, glabrescent. Leaves imparipinnate, with (1-) 2-4 pairs of opposite lateral leaflets; stipules 0.4-1.9 x 0.2-0.5 mm, triangular to lanceolate, strigulose adaxially, glabrescent, caducous; petioles 0.8-3 cm, thinly to moderately strigulose, glabrescent, pulvinus 2-6 mm; rachis (2-) 3.4-8.2 cm, minutely stipellate, unwinged, thinly to moderately strigulose, glabrescent, the stipels <0.5 mm, triangular, caducous; petiolules 1.7-5.9 mm, thinly strigulose, glabrescent; laminas 2.1-3.1 x longer than wide, 5.1-15.5 x 1.8-6 cm, chartaceous, discolorous, elliptic, broadly acute to obtuse at base, acuminate or caudo-acuminate at apex, the acumen rounded, often briefly mucronate, 6-15 mm long, the adaxial surface glabrous, the abaxial surface glabrous to thinly strigulose, with minute simple and malpighian hairs, sometimes canescent, the midrib raised-cariniform on both surfaces, other venation immersed to weakly raised and inconspicuous adaxially, raised abaxially, the secondary veins ca. 8-12, initially ascending at 23-39°, forming loose submarginal loops, each usually with several included intersecondary veins parallel to secondaries. Inflorescences simple racemes or compound racemes with a single order of branching, borne in axils of coeval leaves or from annotinous branchlets, sometimes 2-several-fasciculate, to ca. 20-flowered; axes 2.5-10.5 cm, fairly densely golden-strigulose, glabrescent; bracts 0.7-2.2 (-2.8) x 0.3-1 mm, triangular, ovate or lanceolate, strigulose adaxially; pedicels 3.9-6.5 mm, dorso-ventrally compressed, fairly densely strigulose, glabrescent; bracteoles 0.3-1.9 mm, opposite to subopposite, inserted in distal two-thirds of pedicel, triangular to lanceolate, abaxially strigulose, glabrescent; flower buds 4.1-4.9 x 3.8-4.5 mm, ellipsoid to globose, sometimes apically umbonate, mostly glabrous, but usually strigulose at base. Calyx segments 3-4 in number, ca. 2.5-5.2 x 2.2-4.7 mm, subequal, recurved, elliptic to irregularly shaped, mostly glabrous, often strigulose at base abaxially. Petal yellow, glabrous; claw ca. 2.9 mm; limb broadly ovate, basally truncate, ca. 5.3-7.4 x 5-6.2 mm. Stamens glabrous, dimorphic, of two sizes; larger stamens 4-6 in number, abaxial, the filaments ca. 7.8-8.5 mm, dorso-ventrally compressed, apically tapering, the anthers ca. 1.2 x 0.8-1.1 mm, elliptic in outline; smaller stamens ca. 58 in number, the filaments 4.5-6.1 mm, the anthers 0.8-1.2 x 0.6-0.9 mm, elliptic to rotund in outline. Gynoecium glabrous; stipe 6-6.4 mm; ovary 2.8-3.7 x 1.5-1.9 mm, D-shaped in outline, laterally compressed, the locule glabrous; ovules 8-9; style 0.4-1.1 mm, obliquely terminal to lateral at ovary apex, conical, recurved; stigma punctiform. Fruits green, glabrous; stipe ca. 7-8 mm; body 2.5-2.9 x 1.6-2.4 cm, discoid, broadly elliptic to nearly circular in outline, laterally compressed, rounded at base and apex, but then shortly apiculate at apex by persistent style. Seeds usually 1 per fruit, ca. 2.1 x 1.2 cm, ellipsoid; aril ca. 1.4-1.8 cm long, white, convex-elliptic, covering about a third to half of seed on hilar side.

    Common names: No common names have been recorded.

    Geographic distribution: Swartzia discocarpa occurs in south-central Amazonian Brazil in the state of Pará, where it is known from a handful of collections from several localities in the middle reaches of the basin of the Tapajós River, and from a single locality in the vicinity of Juruti, on the south shore of the Amazon River, to the west of the mouth of the Tapajós River. The distribution may be continuous between these localities, as most of the region has been very poorly collected.

    Ecology: Swartzia discocarpa has been collected in "terra firme" rainforest on sandy and clay soils. One collection was made in a somewhat poorly drained area near a rushing stream. Nothing else is known about the species' ecology.

    Phenology: The timing of flowering may be sporadic or bimodal; the species has been observed with flowers in January, with very immature fruits in November, and with mature fruits in February.

    Taxonomic notes: Swartzia discocarpa possesses the core features of S. sect. Recurvae, including malpighian trichomes, bracteolate pedicels, and the gynoecium with the stipe substantially longer than the ovary proper, a relatively short style and a punctiform stigma. In the balance of characters, it is perhaps most similar to S. leiocalycina of Guyana and Suriname, with which it shares glabrous flowers buds, starkly contrasting with golden-strigulose inflorescence axes and pedicels, and mostly single-seeded, discoid fruits, but it differs from that species in its glabrous to thinly strigulose (versus densely strigulose) abaxial leaflet surface and adaxially raised (versus depressed) leaflet midrib. It is also closely related to S. recurva, with which it undoubtedly co-occurs, but it differs from that species in having smaller, thinner leaves, stipules and bracts, and smaller flowers, with an adaxially glabrous (versus adaxially sericeous) calyx. The collection from Juruti displays relatively long bracts and bracteoles, but is otherwise compatible with other material of the species.

    Uses: No uses have been recorded.

    Etymology: The specific epithet refers to the characteristic shape of the fruits.

    Conservation status: Although current data prevent a definitive conservation assessment, the geographical spread of the localities where the species has been collected indicates that the overall range is large and that the species is probably not currently threatened, although rapidly expanding deforestation and flooding of forests by planned hydroelectric development along the Tapajós River and its tributaries are among a myriad of threats to natural habitats in the region. The species occurs in the Amazonia National Park, south of the city of Itaituba, and is likely present in other protected areas in region.

    References: Cowan, R. S. 1968. Flora Neotropica Monograph No. 1. Swartzia (Leguminosae, Caesalpinioideae, Swartzieae). Hafner Publishing Company, New York and London; Ducke, A. 1935. Plantes nouvelles ou peu connues de la region Amazonienne (VII série). Archivos do Instituto de Biologia Vegetal 2: 27-74; Torke, B. M. & V. F. Mansano. 2009. A phylogentically based sectional classification of Swartzia (Leguminosae-Papilionoideae). Taxon 58: 913-924.

  • Floras and Monographs

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