Swartzia prancei Torke & Mansano

Torke, B.M. & Mansano, V..F. 2013. Increments to the genus Swartzia (Leguminosae) from the southern Amazonian Craton. Kew Bulletin 68: 269. https://doi.org/10.1007/s12225-013-9442-4

Type

Type: Brazil, Mato Grosso, Mun. Aripuanã, near Humboldt Centre, on road to Rio Juruema, 10°12'S, 59°21'W, 8 Oct. 1973, fl., G. T. Prance et al. 18233 (holotype INPA-41538!; isotypes K!, M!, MO!, NY!, U!, US!).

Morphology General Habit

Small tree, reproductive when 3 m tall; pubescence of appressed, fairly straight, golden-tan or whitish, simple or malpighian hairs, mostly less than 0.25 mm long; leaf-bearing portion of branches 1 – 3.5 mm thick at middle of internodes, glabrous to sparsely strigulose

Morphology Leaves

Leaves imparipinnate, with (2 –) 3 pairs of opposite to subopposite lateral leaflets, sometimes with the rachis and terminal leaflet abortive; stipules c. 3.6 – 8.6 × 0.3 – 0.8 mm, filiform-lanceolate, glabrous, caducous; petioles 2 – 4.3 cm long, 1.4 – 1.8 mm thick at middle, basally pulvinate, terete to subterete, unwinged, glabrous to sparsely strigulose, the pulvinus 3.8 – 6.8 × c. 2.6 mm, terete, deeply rugose; rachis 10 – 14 cm long, 0.9 – 1.6 mm thick at middle of segments, terete to subterete, longitudinally bicarinate adaxially, unwinged, glabrous to sparsely strigulose; stipels not seen, apparently caducous; petiolules 4.2 – 5.8 × 1.3 – 2 mm, pulvinular, cylindrical, adaxially canaliculate, deeply rugose, glabrous to sparsely strigulose; laminas 2 – 3 × longer than wide, 7.5 – 15 × 3.9 – 5.7 cm, chartaceous, obovate or elliptic, the distal ones largest and most elongate, the base acute to obtuse, the apex caudo-acuminate, the acumen 9 – 13 mm, rounded, briefly mucronate, the adaxial surface glabrous, the abaxial surface sparingly and minutely malpighio-strigulose, the midrib depressed adaxially, other venation immersed to weakly raised adaxially, all venation salient abaxially, the secondary veins 8 – 12 on each side of midrib, most initially ascending at 22° – 32°, progressively curving upward toward margin, often forming loose submarginal loops in distal half of leaflet, with included intersecondary and tertiary veins more or less parallel to secondaries

Morphology Reproductive morphology Inflorescences

Inflorescences simple racemes, borne from axils of coeval leaves or from defoliate portion of branches, sometimes 2 – several-fascicled, to c. 25-flowered, the flowers spirally arranged; axes (1 –) 4 – 13 cm long, 1.3 – 3.5 mm thick near base, more or less terete, fairly densely tawny-strigulose; bracts 3 – 6 × 1.8 – 3 mm, ovate to elliptic, abaxially concave, apically acute, basally truncate, glabrous adaxially, densely strigulose abaxially, often stipulate, with the stipules to 3.8 mm long, ovate, elliptic, or triangular, often basally fused to bract, sometimes vestigial as dentations on bract margin; pedicels 6 – 14.5 mm long, 1.5 – 2.3 mm thick at middle, dorso-ventrally compressed, densely tawny-strigulose; bracteoles 1.8 – 3.5 mm long, inserted near middle of pedicel, lanceolate or oblanceolate, sometimes more or less spatulate, densely strigulose abaxially; flower buds 6 – 9.5 × 4.7 – 6.8 mm, ellipsoid, apically umbonate, densely tawny-strigulose

Morphology Reproductive morphology Flowers Calyx

Calyx glabrous adaxially, densely strigulose abaxially, sub-actinomorphic, entire in bud, splitting irregularly; segments 3 – 4 in number, c. 6 – 9 × 3.5 – 6.5 mm, sub-equal, more or less elliptic, recurved

Morphology Reproductive morphology Flowers Corolla

Corolla usually monopetalous, occasionally bipetalous; petal adaxial, yellow, glabrous, the claw c. 4.4 – 7.2 mm long, c. 0.7 mm wide at base and 1.7 mm wide at apex, clavate, the limb c. 8.3 – 13 × 8.7 – 13 mm, broadly ovate to orbicular, basally truncate, the venation subpalmate with c. 8 – 10 primary veins, the central vein more robust than others

Morphology Reproductive morphology Flowers Androecium

Androecium glabrous, strongly zygomorphic, the stamens dimorphic and primarily of two size classes; outermost abaxial stamens larger than others, 8 – 10 in number, the filaments 13 – 16.5 mm long, c. 0.4 mm thick at middle, yellow, dorso-ventrally compressed, tapering apically, the anthers 1.3 – 1.9 × 0.9 – 1.1 mm, elliptic in outline; smaller stamens c. 125, adaxial to central on floral axis, the filaments 9 – 13 × 0.1 – 0.2 mm, yellow, terete to elliptic in cross section, the anthers 0.9 – 1.3 × 0.6 – 1 mm, elliptic to oblate-elliptic in outline

Morphology Reproductive morphology Flowers Gynoecium

Gynoecium usually unicarpellate, occasionally with 2 – 3 free carpels, glabrous; stipe 8.5 – 9.5 mm long, c. 0.7 mm thick near middle, terete to elliptic in cross-section, basally and apically dilated; ovary c. 6.2 – 6.5 × 1.8 – 2.1 mm, inequilaterally arcuate-elliptic in outline, laterally compressed, the locule glabrous; ovules c. 8 – 9; style 1.7 – 2.8 × c. 0.5 mm, obliquely terminal, terete; stigma truncate

Morphology Reproductive morphology Fruits

Fruits not seen

Note

Malpighian trichomes, bracteolate pedicels, and a gynoecium with the stipe longer than the ovary proper belie a close phylogenetic relationship between the new species and several species of Swartzia section Recurvae (R. S. Cowan) Torke & Mansano to which it is assigned; in the context of the section, it is unique in having the following combination of characters: lateral leaflets (2 –) 3-paired, the distal ones usually obovate, with the midrib impressed adaxially, bracts 3 – 6 mm long, pedicels 6 – 14.5 mm long, bracteoles 1.8 – 3.5 mm long, flower buds 6 – 9.5 mm long, densely strigulose, larger stamens 8 – 10, gynoecium glabrous.

Swartzia prancei possesses the features of the core members of section Recurvae, including malpighian trichomes, bracteolate pedicels, a rounded to truncate-based petal limb, a unicarpellate gynoecium with the stipe longer than the ovary and a truncate to punctiform stigma. It may be most closely related to other multifoliolate species of the section that have a glabrous gynoecium and a yellow petal, such as S. recurvaPoepp., S. discocarpaDucke, S. krukovii R. S. Cowan, and S. cuspidata Spruce ex Benth., but is unique among them in combining obovate distal leaflets with the midrib adaxially impressed, relatively large bracts and bracteoles and densely strigulose flower buds. Table 2.

The epithet honors the collector of the type specimen, Professor Sir Ghillean T. Prance, for his outstanding contributions to Amazonian botanical exploration.

Distribution

Swartzia prancei is known from only four collections from the vicinity of the Dardanelos waterfall on the Aripuaña River in northwestern Mato Grosso. Map 1.

Ecology

The species has been collected in well-drained terra firme rainforest on mixed sand and clay soils.

Conservation

We assign Swartzia prancei to the Red List category of Data Deficient (DD). The species is known from a very small geographical area, which has been recently altered by the construction of the Dardanelos Dam. It may be of conservation concern, but making a formal assessment as such is in our opinion not advisable at present, since the surrounding region is among the most under-collected parts of the Brazilian Amazon (Schulman et al. 2007).

Phenology

Flowering specimens have been gathered in Sept. and Oct.