Swartzia microcarpa Spruce ex Benth.

Description

Type: Brazil, Amazonas, Rio Uaupes and Rio Paapurés, Nov 1852 (fl), R. Spruce 2619 (holotype: K; isotypes: BM, BR, C, CGE, F, FI, G, GH, GOET, IAN, LE, NY, P, RB, S, US, W).

Description: Tree to 25 m; young branchlets densely tawny-strigulose. Leaves imparipinnate, with (3–) 6–10 alternate to subopposite lateral leaflets, sometimes with the terminal leaflet abortive; stipules ca. 0.3–0.6 x 0.2–0.7 mm, triangular, minute-strigulose adaxially, caducous, sometimes not apparent; petiole 7–24 mm, unwinged, densely tawny-strigulose, the pulvinus 3–8.7 mm; rachis (2.2–) 6–20 cm, unwinged, often somewhat zig-zag, densely tawny-strigulose; stipels absent or minute and caducous; petiolules 3.3–6.1 mm, densely strigulose; laminas 1.7–4 x longer than wide, 4.5–12 x 2–6 cm, chartaceous, mostly elliptic, sometimes oblong, ovate or obovate, the margin often somewhat recuved, the base acute to obtuse-rounded, the apex caudo-acuminate, the acumen pointed, rounded, or weakly retuse, often briefly mucronate, 7.5–18 mm long, the adaxial surface glabrous, the abaxial surface densely tawny-strigulose, with malpighian hairs the midrib depressed adaxially, raised abaxially, other venation raised-prominulous to immersed, the secondary veins 8–15, initially ascending at 18–35°, forming loose submarginal loops, these with one to several included intersecondary veins semiparallel to secondaries but less ascending. Inflorescences simple racemes or compond racemes with a single order of branching, borne from axils of coeval leaves or from annotinous portion of branches, to ca. 25-flowered; axes 5.5–15.5 cm, densely tawny-stigulose; bracts 0.9–3.4 (–5.7) x 0.7–1.9 mm, broadly triangular or ovate to triangular-lanceolate, densely strigulose abaxially; pedicels 8–16.6 mm, dorso-ventrally compressed, dilated apically, densely tawny-strigulose; bracteoles 0.7–2.2 mm, opposite to subopposite, inserted in the distal third of pedicel, ovate or triangular to ovate-lanceolate; flower buds 7.7–10.6 x 6.5–8.6 mm, ellipsoid, umbonate, densely tawny strigulose. Calyx segments 3–5 (–6) in number, 5–10 x 2.5–7 mm, subequal, elliptic, oblong or irregularly shaped, strongly recurved, glabrous adaxially, densely tawny-strigulose abaxially. Petal yellow, glabrous; claw 2.8–5.3 mm; limb broadly ovate or rotund, the base truncate or subcordate, 7.3–17.5 x 7.9–18.3 mm. Stamens glabrous, dimorphic, of two size classes; larger stamens ca. 7 in number, the filaments 10–16 mm, dorso-ventrally compressed basally, tapering apically, the anthers 1.3–2.2 x 0.8–1.4 mm, elliptic in outline; smaller stamens 140–180 in number, the filaments 4–13 mm, the anthers 0.7–1.4 x 0.7–1 mm, elliptic to rotund in outline. Gynoecium with the stipe 8.4–16.2 mm, linear-cylindrical, slightly dilated at base and apex, arcuate, mostly glabrous, becoming densely malpighio-strigulose toward apex; ovary 5.4–9.4 x 2.7–4.1 mm, inequilaterally arcuate-elliptic in outline, laterally compressed, densely golden malpighio-strigulose, the locule glabrous; ovules 5–6; style 2.5–5.3 mm, obliquely terminal, arcuate, basally dilated, mostly glabrous, becoming densely malpighio-strigulose toward base; stigma punctiform. Fruits with the stipe 1.6–2.1 cm patchily strigulose, glabrescent; body 6.5–8.8 (–12) x 4–5.5 cm, elliptic to obovate in outline, laterally compressed, broadly acute to obtuse at base, obtuse or rounded at apex, then briefly acuminate by persistent style, the surface shallowly rugose to verrucose, densely ferruginous-strigulose, sometimes glabrescent on the somewhat raised sutures. Seeds 1 (–2) per fruit, ca. 5 x 3–3.5 cm, more or less elliptic in outline, laterally compressed; aril ca. 2.5 x 0.9 cm, oblong, marginal on hilar side of seed.

Common names: No common names have been recorded.

Geographic distribution: Swartzia microcarpa occurs at less than 500 m elevation in the upper drainage of the Orinoco River in Venezuela, specifically the tributaries that drain the western and southern slope of the Cerro Ouana, the Serranía Guayapu and associated uplands, including the Autana, Sipapo and Guayapo Rivers. To the south, it is apparently distributed broadly in the upper Negro River drainage of southern Venezuela, northwestern Brazil and eastern Colombia, ranging as far south as the Apaporis drainage in Colombia. The extent to which widely separated collection localities reflect disjunctions in the range is unclear, since the intervening areas are for the most part highly under-sampled.

Ecology: The species occurs in both upland terra firme and in seasonally inundated forest along rivers. In the former, it seems to be most prevalent in somewhat stunted forest near small streams or in areas with poor drainage, where it may occur in association with Eperua purpurea (Aymard et al. 12695), a characteristic element of this vegetation type in the upper Rio Negro region. Near the village of Mitú in Colombia, the present author found saplings of S. microcarpa to be a fairly common in such forest, usually over white sand, but failed to find the species in the true “igapo” forest along the Vaupés River. On the other hand, in the upper Rio Orinoco, the species is perhaps restricted to seasonally inundated riverside vegetation, of which it is reported to be a common element (Foldats & Velazco 9435).

Phenology: Flowering has been observed in October and November, mature or nearly mature fruits in February, March, May and June.

Taxon notes: Swartzia microcarpa was assigned to section Recurvae by Torke & Mansano (2009), based partly on the results of the molecular phylogenetic analysis of Torke & Schaal (2008). In terms of morphology, the species is unusual in the genus in its typically alternate leaflets and among con-sectional species in its densely strigulose ovary. But in most other respects —malpighian trichomes, caudo-acuminate leaflets, bracteolate pedicels, and the form and proportions of the gynoecium— it fairly closely resembles most other species of section Recurvae. The leaflets, which are densely fulvous pubescent underneath, are reminiscent of those of S. leiocalycina, whereas the alternate arrangement of the leaflets, while it occurs sporadically in other species of Swartzia, appears as a semi-fixed state only in S. microcarpa and S. alternifoliolata. In Torke and Schaal’s (2008) analysis of combined molecular data, S. microcarpa was weakly resolved as the sister taxon of S. cuspidata, from which it is immediately separable by its densely strigulose lower leaflet surface, flower buds, and ovary. The single flowering specimen from the Orinoco drainage (Castillo 6907) differs from other flowering material of the species in having larger bracts (2.5–5.7 mm versus 0.9–1.7 mm), pedicels (12.5–16.6 mm versus 8–11.4 mm), bracteoles (1.6–2.2 mm versus 0.7–1 mm) and flower buds (7.7–10.6 mm versus 6–7.9 mm), and also in its larger petal with the claw proportionately shorter (ca. 2.8 mm versus 3.4–5 mm) and the base of the limb subcordate (versus truncate). We suspect that these differences are worthy of taxonomic recognition, perhaps at the subspecific level, but additional specimens from the Orinoco basin are needed to better document these potential morphological distinctions.

Uses: No uses have been recorded.

Etymology: The epithet meaning “small fruit” presumably was given in reference to several other species of the genus with much larger fruits that were encountered by Richard Spruce during his travels in Amazonia.

Conservation status: The species is not currently threatened. Although the total number of collections is small, S. microcarpa ranges across a broad geographical distribution, parts of which span large areas of intact Amazonian wilderness. It is likely present in a number of nominally protected areas.

Floras and Monographs

Swartzia microcarpa Spruce ex Benth.: [Article] Cowan, Richard S. 1967. Swartzia (Leguminosae, Caesalpinioideae Swartzieae). Fl. Neotrop. Monogr. 1: 3-228.

Map Distribution

View all records of Swartzia microcarpa Spruce ex Benth.

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