Torke, Benjamin M. & Zamora Villalobos, Nelson A. 2010. Notes on
Fabaceae
Description - Evergreen tree to ca. 5 m tall, reproductive when less than 2 m tall, the trunk to ca. 7 cm in diameter; bark smooth, gray; exudate scant, clear; pubescence of simple, relatively straight, appressed to semi-erect hairs, mostly 0.15-0.5 mm long; leaf-bearing branchlets terete to somewhat angular in cross-section, 0.8-1. 5 (-2. 5) mm thick, sparsely to densely strigose-pilose. Leaves stipulate, alternate, spiral on interior branches, distichous on distal branchlets, imparipinnate, with 1-4 pairs of opposite lateral leaflets; stipules filiform, 1.5-4 mm long, ca. 0.2 mm wide at base, strigose-pilose abaxially; petioles alate, the wing similar to those on the rachis, basally pulvinate, 2-8 mm long; rachis individually alate between leaflets, caniculate and strigose-pilose or glabrescent between wing lobes adaxially, rounded and moderately to densely strigose-pilose abaxially, (1-)2.5-6 (-7) cm long, the wings narrowly obtriangular, nearly covering the petiolules, apically stipellate, reticulate-venulose, 1.5-3(-4) mm wide just below stipels, essentially glabrous; petiolules pulvinate, terete, 0.6-1 (-1.3) x 0.5- 0.9 mm, strigose-pilose, often densely so; leaflet blades membranaceous to chartaceous, those of the terminal leaflet oblong-elliptic, larger than the others, (3.3-)4-8.5x(1-)1.4- 3.1 cm, those of the upper lateral leaflets oblong-elliptic, 3-5.8 x 1-1.9 cm, those of the lowermost lateral leaflets broadly elliptic or ovate, (1.3-)2-3.1x(0.8-)1-1.8 cm, all blades mostly glabrous, strigose-pilose on the midrib, the base broadly acute, obtuse, or rounded, the apex abruptly acuminate, the acumen obtuse or rounded, briefly mucronate, 0.6-1.3 cm long on terminal leaflets, the midrib and other venation prominent on both surfaces, the secondaries brochidodromous, the intersecondaries and tertiaries relatively straight and parallel to secondaries, the higher order veins intricately reticulate. Inflorescences racemose, occasionally 1 -branched, arising from the axils of current leaves, 1 -several- flowered, the flowers more or less spirally arranged, the axes green, more or less terete, (1.4-)2.2-7.8 cmx0.5-0.8 mm, moderately to densely strigose-pilose; bracts elliptic, convex, 0.6-1.2 xca. 0.5 mm, strigose-pilose abaxially, stipulate, the stipules similar to those of the foliage leaves, (0.5-)1. 1-2.2 xCa. 0.1 mm; pedicels terete, 7.5-20 xca. 0.6 mm, moder- ately to densely strigose-pilose; bracteoles lacking; flower buds green, globose to weakly ellipsoid, 5.7-6.7 mm long and nearly as wide, mostly glabrous, sparsely strigose basally. Calyx more or less actinomorphic, entire in bud, splitting irregularly, sparsely strigose at base abaxially, otherwise glabrous, the segments usually 4, sub-equal, ovate to elliptic, basally truncate, apically acute to obtuse, strongly deflexed, the margins recurved, 6.7- 8.4x3-5 mm. Corolla monopetalous, the petal adaxial, yellow, membranaceous, mostly glabrous, sometimes sparsely strigose on the central vein abaxially, clawed, the claw ca. 1 mm long and roughly as wide at the base, dilated apically, the blade oblate, the base broadly rounded, obtuse or truncate, 9.8- 1 1.6 x 11.5-12.4 mm, the margin undulate, the venation sub-palmate, with ca. 8 primary veins, the central vein more robust than the others. Androecium zygomorphic, glabrous, the stamens of two sizes, the larger stamens 5-7, abaxial, in a single row, the filaments yellow, somewhat compressed longitudinally, tapering apically, 7-9 mm long, ca. 0.4 mm thick near base, the anthers oblong in outline, ca. 2.3 x 1 mm, the smaller stamens 80-90, mostly adaxial, in several rows, the filaments yellow, terete, 4-8 xca. 0.05 mm, the anthers oval in outline, ca. 0.8x0.7 mm. Gynoecium mono- pistillate, light green, glabrous or nearly so, sometimes sparsely pubescent on the stipe, the stipe oval in cross section, dilated basally and apically, 4-4.7 mm long, ca. 0.4 mm thick near middle, the ovary acuate-elliptic in outline, compressed laterally, 3.7-4.2x1.1-1.5 mm, the style lateral or oblique, not well differ- entiated from the ovary, conical, 0.3-0.4 mm long, the stigma punctiform or more or less truncate. Fruits maturing bright orange, glabrous, dehiscing along both margins, the stipe terete, dilated basally and apically, 0.6- 1 cm long, ca. 1 mm thick at center, the body plumply ellipsoid, 1.9-2.6x1.1-1.5 cm, the persistent style oblique, ca. 0.4 mm long. Seeds 1 per fruit, maturing black, reniform, adaxially concave, ca. 2.1x1x0.8 cm, the aril adaxial, white, fleshy, fimbriate, convex, ca. 1.8x1.3 cm flattened, covering ca. one-third of seed.
Distribution, habitats, and conservation status. - Pacific slope and adjacent lowlands of central and southern Costa Rica, in the states of San José and Puntarenas, from Cantón Turrubares to Golfito, apparently absent from all but the northern portion of the Osa Peninsula (Fig. 2). Swartzia picramnioides grows in humid forests on clay soils often on slopes or near streams from sea level to about 1000 m elevation, with most collections com- ing from 200 to 500 m. Although the geographic distribution of S. picramnioides is relatively small, overall the species is probably not threatened. It is locally common in appropriate habitats and appears to be moderately tolerant of forest disturbance. The species is represented in several protected areas.
Phenology. - Flowering June to August, fruiting September to February. Taxonomic history and etymology. - The binomial Swartzia picramnioides was appar- ently coined by P. C. Standley and L. O. Williams based on a fruiting collection, P.H. Allen 5815 (M. H. Grayum, pers. comm.) but it was never validly published. It appeared along with several other unpublished names attributed to Standley and Williams "im the book The Rain Forests of Golfo Dulce" by Allen (1956). Other examples include "Octea pergamentacea Standley & L.O. Williams," subsequently published as Licaria pergamentacea W.C. Burger, and "Senecio iltisii Standley & L.O. Williams, " published as S. costaricensis R. M. king. On pages 332-333 of his book, Allen gives a brief description of Swartzia picramniodes but does not provide a latin diagnosis. The specific epithet presumably refers to the superficial resemblance of the leaves to some species of Picramnia (Picramniaceae).
By virtue of its few-flowered, axillary inflorescences, stipulate bracts, ebracteolate pedicles, and yellow, petalous flowers, Swartzia picramnioides belongs to section Possira as defined by Torke and Mansano (2009). In the molecular phylogenetic analyses of Torke and Schaal (2008), S. picramnioides (referred to as "S. sp. nov. C") was placed as the sister taxon of S. standleyi. Phylogeographic analysis (V. F. Mansano, B. M. Torke, & C. Addis, unpubl. data) suggests that both species are part of the "S. guatemalensis species group." Morphologically, S. picramnioides is perhaps most similar to the South American species, S. myrtif Sm. In particular, it shares many characters with the eastern Brazilian taxon, S. myrtifolia var. elegans (Schott) R. S. Cowan, which itself is probably deserving of specific recognition. Both have a regularly winged rachis, a ten- dency toward relatively numerous, abruptly acuminate leaflets, and relatively few larger stamens. However, the Costa Rican species stands apart from all other taxa of section Possira in the form and proportions of the gynoecium. The style is reduced far beyond that of any other species, a feature that is observable in fruiting as well as flowering specimens, and the ovary is smaller and less elongate than in consectional taxa in Central America. In addition, the species is unique in the section in having a punctiform or truncate (vs. capitellate) stigma.
Swartzia picramnioides is broadly sympatric with the more widespread species S. simplex. Both species are variable within the area of distributional overlap. At higher elevations in San Jose province S. simplex tends to have trifoliolate leaves; in Puntaraenas the leaves are uniformly unifoliolate. Similarly, leaflet number tends to decrease southward in the distribution of S. picramnioides, with some collections from southern Puntarenas being uniformly trifoliolate. However, S. picramnioides differs consistently from S. simplex in the gynoecial characters mentioned above and elaborated in the key that follows, and also in its typically more numerous and smaller, abruptly acuminate (vs. acute to weakly acuminate), membranaceous to thinly chartaceous (vs. subcoriaceous) leaflets