Swartzia rondoniensis 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. Rondônia, 13.5 km from Alvoradad’Oeste, Line 64, road to Nova Brasilândia [d’Oeste], left side, 25 Sept. – 31 Oct. 1986, fl., L. C. B. Lobato et al. 352 (holotype MG-124667!).

Morphology General Habit

Tree to c. 13 m; trunk to c. 30 cm in diam.; pubescence of appressed, fairly straight, golden-tan or whitish, simple or malphigian hairs, mostly less than 0.25 mm long; leaf-bearing portion of branches 2 – 3 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 1 – 11.5 × 0.3 – 1 mm, triangular to lanceolate, often falcate, glabrous, parallel-veined, caducous; petioles 0.9 – 3.8 cm long, 0.8 – 1.5 mm thick at middle, basally pulvinate, terete to subterete, unwinged, glabrous to sparsely strigulose, the pulvinus 2.5 – 7.8 × 1.2 – 2.1 mm, terete, deeply rugose; rachis (1.5 –) 3 – 11 cm long, 0.7 – 1.5 mm thick at middle of segments, terete to subterete, longitudinally bicarinate to narrowly marginate adaxially, unwinged, glabrous to sparsely strigulose; stipels not seen, apparently caducous; petiolules 2.6 – 6.4 × 0.8 – 1.4 mm, pulvinular, cylindrical, adaxially canaliculate, deeply rugose, glabrous to sparsely strigulose; laminas 1.9 – 3.5 × longer than wide, (4 –) 5.5 – 13 × (1.8 –) 2.5 – 5 cm, chartaceous, mostly elliptic, the distal ones largest and most elongate, the base acute to obtuse, the apex caudo-acuminate, the acumen 7 – 15 mm, rounded or somewhat retuse, often briefly mucronate, the adaxial surface glabrous, the abaxial surface essentially glabrous to thinly and minutely malpighio-strigulose, the midrib usually somewhat raised-cariniform adaxially, other venation weakly raised adaxially, all venation salient abaxially, the secondary veins 8 – 12 on each side of midrib, most initially ascending at 20° – 35°, progressively curving upward, forming loose submarginal loops in distal half of leaflet, usually with included intersecondary and tertiary veins more or less parallel to secondaries

Morphology Reproductive morphology Inflorescences

Inflorescences simple racemes or compound racemes with a single order of branching, borne from axils of coeval leaves or from defoliate portion of branches, sometimes 2 – several-fascicled, to c. 30-flowered, the flowers spirally arranged; axes 1 – 11 cm long, c. 1.2 – 2.5 mm thick near base, terete or elliptic in cross section, often somewhat angular, fairly densely tawny-strigulose; bracts mostly 1 – 2.5 × 0.8 – 1.8 mm, triangular, ovate or elliptic, apically acute to obtuse, basally truncate, the lowermost often leaf-like, with a rachis, leaflets, and stipules, glabrous adaxially, thinly to somewhat densely tawny-strigulose abaxially, the stipules when present, 0.2 – 1.3 mm, triangular, ovate, or subulate, sometimes adnate to bract basally; pedicels 6 – 10.5 mm long, 1.5 – 2.5 mm thick at middle, dorso-ventrally compressed, apically dilated, fairly densely tawny-strigulose; bracteoles 1 – 1.7 mm, inserted near apex of pedicel, ovate or lanceolate, tawny-strigulose abaxially; flower buds 4.4 – 7.6 × 3.9 – 6.1 mm, ellipsoid, ovoid or globose, apically rounded to acute, umbonate, evenly and fairly densely tawny-strigulose

Morphology Reproductive morphology Flowers Calyx

Calyx light green when fresh, glabrous adaxially, strigulose abaxially, sub-actinomorphic, entire in bud, splitting irregularly; segments 4 – 5 in number, 2.8 – 6.5 × 1.8 – 5 mm, subequal, more or less elliptic, recurved

Morphology Reproductive morphology Flowers Corolla

Corolla monopetalous; petal adaxial, yellow, glabrous, the claw 3 – 5 mm long, c. 0.5 mm wide at base and 1.2 mm wide at apex, basally truncate, apically dilated, the limb 8.1 – 13 × 7.9 – 11.8 mm, ovate to orbicular, basally truncate, the venation subpalmate with c. 9 – 11 primary veins, the central vein more robust than others

Morphology Reproductive morphology Flowers Androecium

Androecium glabrous, strongly zygomorphic, the stamens primarily of two size classes or with intergradations between sizes; outermost abaxial stamens, when clearly differentiated and larger than the others, 6 in number, the filaments c. 14 mm long, 0.3 – 0.5 mm thick at middle, yellow, dorso-ventrally compressed, tapering apically, the anthers c. 1.3 – 1.6 × 1 – 1.2 mm, elliptic in outline; smaller stamens c. 145 – 190, adaxial to central on floral axis, the filaments (2.5 –) 6 – 12 × 0.1 – 0.3 mm, yellow, terete to elliptic in cross section, the anthers 0.7 – 1.1 × 0.7 – 0.9 mm, elliptic to oblate-elliptic in outline

Morphology Reproductive morphology Flowers Gynoecium

Gynoecium unicarpellate, glabrous; stipe 7.3 – 8.8 mm long, c. 0.7 mm thick at middle, light green, turning dull purple, more or less terete, basally and apically dilated; ovary 5.8 – 6.7 × 1.4 – 2 mm, light green, narrowly acuate-elliptic in outline, laterally compressed, the locule glabrous; ovules c. 8 – 9; style 1.2 – 2.8 × c. 0.5 mm, light green, turning dull purple, obliquely terminal, terete; stigma punctiform

Morphology Reproductive morphology Fruits

Mature fruits not seen; immature fruits green to yellow, glabrous, with the stipe 12 – 15 × c. 1 mm, terete, the body to c. 3.4 × 1.3 cm, smooth, becoming more or less elliptic in outline, laterally compressed, the persistent style terminal to somewhat oblique

Distribution

Swartzia rondoniensis is known from two widely separated areas in the rainforest-savanna transition of southern Amazonia. The majority of the collections were gathered in tributary drainages of the upper Madeira River in the state of Rondônia, while a single collection was made in the state of Pará, near the border with Tocantins and Maranhão, in the basin of the Tocantins River. Map 1.

Ecology

Swartzia rondoniensis has been collected at less than 500 m elevation in well-drained terra firme rainforest, in seasonally flooded riverine varzea forest and in shrubby savanna (cerrado) with bamboo.

Conservation

The species is assigned to the IUCN Red List category of Near Threatened (NT, criterion A2, applied as for Swartzia arumateuana). Assuming that the disjunction between populations in Rondônia and Pará is real, and not just an artifact of sampling, both areas that comprise the extent of occurrence are located within regions where the conversion of forest and natural savannas for soybean cultivation and for grazing pastures dominated by alien plants is rampant.

Phenology

The species apparently flowers from Sept. to Feb.

Note

Another new member of section Recurvae, Swartzia rondoniensis is closely related to the proceeding species, as well as to several other members of the section with multifoliolate leaves and glabrous gynoecia, such as S. cuspidata, S. krukovii and S. recurva. Characters that in combination distinguish S. rondoniensis are 2 – 3 pairs of lateral leaflets, an adaxially raised leaflet midrib, uniformly strigulose flower buds, and relatively small stipules, bracts and bracteoles. Table 2.

The epithet connotes the Brazilian state from which the type and several other collections were gathered.

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 to which it is assigned; in the context of the section, it is unique in the following combination of characters: stipules 1 – 11.5 mm long, leaf rachis unwinged, lateral leaflet pairs 2 – 3, nearly glabrous with the midrib raised adaxially, bracts 1 – 2.5 mm long, pedicels 6 – 10.5 mm long, flower buds 4.4 – 7.6 mm long, uniformly strigulose, petal yellow, gynoecium glabrous.

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