Swartzia rugosa Torke & Mansano

Extinction risk predictions for the world's flowering plants to support their conservation (2024). Bachman, S.P., Brown, M.J.M., Leão, T.C.C., Lughadha, E.N., Walker, B.E. https://nph.onlinelibrary.wiley.com/doi/full/10.1111/nph.19592

Conservation

Predicted extinction risk: threatened. Confidence: confident

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, Pará, Mun. Senador José Porfírio, Rio Bacajás, hill on left bank, near Fazenda Sipaúba, 16 March 1987, fl., S. A. M. Souza et al. 1243 (holotype RB-390888!; isotypes MG!, NY!).

Morphology General Habit

Tree to c. 10 m, sometimes reproductive when only 2 – 3 m tall; trunk to c. 30 cm in diam.; pubescence golden, of two types, on vegetative organs erect, the trichomes straight or uncinate, these often exceeding 0.4 mm long, on reproductive organs, appressed, the trichomes mostly less than 0.4 mm long; leaf-bearing portion of branches 2.2 – 4.5 mm thick at middle of internodes, tawny-pilose to villous

Morphology Leaves

Leaves imparipinnate, with (3 –) 4 – 5 pairs of opposite lateral leaflets; stipules 5.5 – 29 × 1.8 – 8 mm, ovate-lanceolate, oblanceolate or elliptic, densely tawny-sericeous to villous, glabrescent; petioles 1.2 – 5.2 cm long, 1.5 – 3 mm thick at middle, basally pulvinate, more or less terete, tawny-pilose to villous, the pulvinus c. 2.5 – 6.5 × 2 – 4.3 mm, terete, basally dilated, often obscured by dense pubescence; rachis 7 – 26 cm long, 0.8 – 2.3 mm thick at middle of segments, individually winged between leaflet pairs adaxially, longitudinally sulcate between halves of wing lobes, tawny-pilose to villous, the wing lobes 2.5 – 10 mm wide measured across rachis at widest point, narrowly obtriangular-clavate, bidentate and stipellate apically, venulose, glabrous to sparingly pilose adaxially, more densely pilose abaxially; stipels 0.6 – 3.5 mm long beyond wing, c. 0.2 mm wide, subulate; petiolules 0.6 – 2 × 1.1 – 2.2 mm, pulvinular, cylindrical, adaxially canaliculate, densely pilose to villous; laminas 1.9 – 4.1 × longer than wide, 4.5 – 20 × 2.2 – 6.5 cm, membranous to thinly chartaceous, rugose-bullate adaxially, oblanceolate, oblong-elliptic, elliptic, or obovate, the distal (or medial) ones largest and most elongate, the base acute, obtuse, or rounded, the apex gradually acuminate, occasionally acute or more or less rounded, the acumen pointed or rounded, often briefly mucronate, the adaxial surface mostly glabrous, pilose-villous on midrib, the abaxial surface pilose, the midrib and other veins strongly impressed adaxially, conspicuously raised abaxially, the secondary veins 11 – 18 on each side of midrib, most initially ascending at 15 – 35°, curving upward distally and forming submarginal loops, these with included intersecondary veins semiparallel to but usually less ascending than secondaries, the tertiary veins mostly more or less perpendicular to secondaries

Morphology Reproductive morphology Inflorescences

Inflorescences simple racemes, borne from nodes on defoliate portion of branches or on trunks, to c. 50-flowered, the flowers spirally arranged; axis 15 – 30 cm long, 2.5 – 3.5 mm thick near base, terete, thinly golden-stigulose to pilosulous; bracts 2.5 – 6.5 × 1 – 2 mm, ovate to narrowly triangular, apically acute, basally truncate, glabrous adaxially, strigulose abaxially; pedicels 15 – 28 mm long, 1 – 1.5 mm thick at middle, somewhat dorso-ventrally compressed, thinly to fairly densely golden-strigulose; bracteoles lacking; flower buds 6.3 – 8.4 × 5.7 – 7.8 mm, globose, ellipsoid or oblate, weakly umbonate, thinly golden-strigulose

Morphology Reproductive morphology Flowers Calyx

Calyx sub-actinomorphic, entire in bud, splitting irregularly, mostly glabrous adaxially but strigulose centrally at insertion of stamens, thinly strigulose abaxially; segments 4 – 5 in number, 5 – 7.5 × 4 – 5.6 mm, subequal, more or less elliptic, recurved

Morphology Reproductive morphology Flowers Corolla

Corolla monopetalous; petal adaxial, thinly strigose on veins abaxially, the claw 1.2 – 1.4 mm long, 0.9 – 1.2 mm wide at base, 1.4 – 1.8 mm wide at apex, apically dilated, basally rounded, the limb 10.5 – 12.5 × 9.8 – 12 mm, broadly elliptic to orbicular, basally truncate, the venation palmate, with 5 – 9 primary veins, the central one more robust than others

Morphology Reproductive morphology Flowers Androecium

Androecium glabrous, strongly zygomorphic, the stamens dimorphic, primarily of two size classes; outermost abaxial stamens larger than others, 9 – 11 in number, the filaments 11.5 – 15.2 mm long, c. 0.6 mm thick at middle, dorso-ventrally compressed, tapering apically, the anthers 2.9 – 4.1 × 1.1 – 1.5 mm, oblong in outline, the connective apically acute to obtuse, prolonged beyond thecae; smaller stamens c. 130, adaxial to central on floral axis; the filaments 12 – 13 × c. 0.1 mm, terete to elliptic in cross section, often shortly fused basally in groups of two to several, the anthers 1.2 – 1.9 × 0.6 – 1.2 mm, ovate to oblong-elliptic in outline, the connective apically acute to obtuse, notably prolonged beyond thecae

Morphology Reproductive morphology Flowers Gynoecium

Gynoecium unicarpellate, thinly strigose, except on glabrous stigma; stipe 5.3 – 7 mm long, c. 0.6 mm thick at middle, terete to elliptic in cross section, plumply dilated at base, gradually so at apex; ovary 11 – 14 × 1.3 – 1.7 mm, acuate-filiform, laterally compressed, the locule glabrous; ovules c. 13; style 0 – 1.3 mm × c. 0.6 mm, terminal, terete; stigma obliquely truncate

Morphology Reproductive morphology Fruits

Fruits (slightly immature) green, c. 1 – 11-seeded; stipe c. 1 cm × 2 mm, more or less terete, thinly strigulose, glabrescent; body c. 7 – 30 cm long, 1.3 – 2 cm wide at seed compartments, 0.3 – 1.5 cm wide at constrictions between seeds, ellipsoid to linear-moniliform, somewhat arcuate, variously constricted between seeds, narrowly attenuate at base and apex, the sutures raised, the valve faces minutely venulose-rugose, glabrescent, but usually remaining thinly strigulose at base and apex and on constrictions

Morphology Reproductive morphology Seeds

Seeds 2.1 – 2.6 × 1.4 – 1.5 cm, ellipsoid, obovoid or ovoid, the testa chartaceous; aril c. 2.2 – 2.7 × 1 cm, fleshy, oblong, semi-encircling hilar side of seed along its longitudinal axis

Distribution

The four existing collections of Swartzia rugosa were taken from the vicinity of the Tucuruí Reservoir on the lower Tocantins River and the soon-to-be constructed Belo Monte Dam on the lower Xingu River. Map 2.

Ecology

The species occurs at upland terra firme sites, at less than 500 m elevation, with open forest, apparently with a prevalence of babaçu palms (Attaleaspeciosa Mart. ex Spreng.) and lianas, on both sandy and clay soils. One collection was reportedly taken in ‘sub-montane’ forest.

Conservation

We assign Swartzia rugosa to the IUCN Red List category of Near Threatened (NT, criterion A2, applied as for S. arumateuana). The known distribution overlaps with that of S. arumateuana, but the comparative paucity of collections of S. rugosa suggests that the species is either rare or more restricted in habitat and/or distribution. Ongoing threats in the documented extent of occurrence include rapidly expanding cattle ranching, agriculture, mining, hydroelectric development, settlement and urbanisation.

Phenology

Flowers have been observed in March, Aug. and Sept., fruits in Nov.

Note

The specific epithet refers to the bullate-rugose texture of the leaflets.

Ebracteolate pedicels, a yellow petal, a filiform gynoecium, with the ovary longer than the stipe and style and moniliform fruits suggest a close phylogenetic relationship between the new species and several species of Swartzia section Terminales, to which it is assigned; in the context of the section, it is unique in the following combination of characters: leaflets conspicuously bullate-rugose from the adaxially impressed venation, pilose on the abaxial side, with the trichomes mostly 0.1 – 0.5 mm long, pedicels 15 – 28 mm long, flower buds 6.3 – 8.4 × 5.7 – 7.8 mm, larger stamens 9 – 11, ovary 11 – 14 × 1.3 – 1.7 mm, thinly strigose, fruits linear-moniliform, variously constricted between the 1 – 11 seeds.

Another new member of section Terminales, Swartzia rugosa is most similar to S. obscura Huber, which also occurs in eastern Amazonia, but mainly north of the Amazon River. It differs from that species in its winged leaf rachis, conspicuously bullate-rugose leaflets, dull-green (vs glaucous) lower leaflet surface, more numerous larger stamens and less consistently fused smaller stamen filaments, which in S. obscura are united in a column for approximately the basal half of their length. The two species also usually differ in the orientation of the pubescence on the leaflet undersurface, which is erect in S. rugosa and appressed in most individuals of S. obscura. The bullate-rugose leaflets are similar to those of S. corrugataBenth., another member of section Terminales found in central Amazonia, but S. corrugata has an unwinged leaf rachis, smaller flower buds and flower parts, 3 – 6 larger stamens, and a more densely pubescent, less elongate gynoecium.