Solanum pygmaeum Cav., Icon. 5: 23, tab. 439. 1799.

Knapp, Sandra, Saerkinen, Tiina & Barboza, Gloria E., 2023, A revision of the South American species of the Morelloid clade (Solanum L., Solanaceae), PhytoKeys 231, pp. 1-342 : 1

45. Solanum pygmaeum Cav., Icon. 5: 23, tab. 439. 1799.

Figs 137 , 138

Solanum pygmaeum Cav. var. hastatum Bonte ex Aellen, Ber. Schweiz. Bot. Ges. 50: 236. 1940. Type. Argentina. Buenos Aires: Pergamino, J.A. de la Peña, 14 Jan 1925, L.R. Parodi 6107 (lectotype, designated here: BAA [BAA00004675]).

Solanum pygmaeum Cav. var. suspensum C.V.Morton, Revis. Argentine Sp. Solanum 138. 1976. Type. Argentina. Córdoba: Alta Córdoba, barrio de la ciudad de Córdoba, T. Stuckert 4713 (holotype: G; isotypes: CORD [CORD00004273, CORD00004274]).

Solanum deterrimum C.V.Morton, Revis. Argentine Sp. Solanum 138. 1976. Type. Argentina. Buenos Aires: Sierra de la Ventana, 23 Feb 1944, H. Ruíz de Huidrobo 1332 (holotype: A [00077613]; isotypes: NY [00139129], S [acc. # 12-27773], SI [003308, 003307]).

Type.

Argentina. Buenos Aires: "in Pampas de Buenos Ayres esquina de Ballesteros", Sep, L. Née, s.n. (lectotype, designated by Knapp 2007, pg. 200: MA [MA-476361]; isolectotype: G [G00357891]) .

Description.

Perennial small upright herbs to 0.3 m high, subwoody at base, perennating via underground rhizomes. Stems decumbent or ascending, delicate, terete or somewhat angled with ridges, not markedly hollow; new growth pubescent with simple, appressed, uniseriate, translucent, eglandular trichomes, these 1-6-celled, 0.2-0.5 mm long, or nearly glabrous; older stems glabrous or glabrescent. Sympodial units difoliate, the leaves not geminate. Leaves simple, occasionally lobed, the blades 1-5 cm long, 0.5-3 cm wide, ovate to narrowly elliptic, widest in the lower half or near the middle, membranous, concolorous; adaxial surface glabrous or sparsely pubescent along leaf lamina and margins with simple, uniseriate trichomes like those on stem; abaxial surface sparsely pubescent with similar trichomes but the pubescence denser along the midrib; major veins 3-4 pairs; base attenuate, decurrent on the petiole; margins sinuate to entire, if sinuate then teeth more common in lower part of the blade; apex acute to obtuse; petioles 0.5-1.7 cm long, with scattered simple, appressed, uniseriate eglandular trichomes like those on stem. Inflorescences generally internodal, unbranched or rarely forked, umbelliform to subumbelliform, 1-3 cm long, with (2-)4-6 flowers clustered at the tip, glabrous or with scattered simple, appressed, uniseriate eglandular trichomes like those on stem; peduncle (1.3-)1.5-2.6 cm long, delicate; pedicels 6-13 mm long, 0.5-1 mm in diameter at the base, ca. 1 mm in diameter at the apex, straight and spreading, articulated at the base; pedicel scars spaced ca. 0-2.5 mm apart. Buds globose to broadly ovoid, the corolla strongly exserted from the calyx tube but only halfway exserted beyond the elongate and reflexed calyx lobes before anthesis. Flowers 5-merous, cosexual (hermaphroditic). Calyx tube (0.5-)1.7-2(-2.2) mm long, conical, the lobes 1.5-1.8 mm long, 0.7-0.9 mm wide, narrowly elliptic with long-acuminate to acute apices, glabrous to sparsely pubescent with simple uniseriate eglandular trichomes like those on stem. Corolla 0.9-1.6 cm in diameter, white to pale lilac with a yellow-green central portion near the base, stellate, lobed halfway to the base, the lobes 5-6.7 mm long, ca. 3-3.5 mm wide, strongly reflexed at anthesis, later spreading, glabrous to sparsely pubescent abaxially with simple uniseriate trichomes like those of the stem but shorter. Stamens equal; filament tube minute; free portion of the filaments 1-1.2 mm long, adaxially pubescent with tangled uniseriate 4-9-celled eglandular trichomes to 0.5 mm long; anthers (3-)3.5-3.8 mm long, 0.7-1 mm wide, oblong-ellipsoid, yellow, poricidal at the tips, the pores lengthening to slits with age and drying. Ovary globose, glabrous; style ca. 6.3 mm long, straight, exserted beyond the anther cone, densely pubescent with (1-)2-3-celled simple uniseriate trichomes along 4/5 from the base; stigma capitate to clavate, bilobed, minutely papillate, green in live plants. Fruit a subglobose berry, 0.8-1 cm in diameter, greyish green at maturity, the pericarp opaque and glaucous, glabrous; fruiting pedicels 12-15 mm long, ca. 1 mm in diameter at the base and at the apex, deflexed and often somewhat curved, not persistent; fruiting calyx not accrescent, lobes 1.5-2 mm long, lobes appressed against the berry. Seeds 30-more than 50 per berry, 1.8-2 mm long, 1.2-1.4 mm wide, flattened and teardrop shaped with a subapical hilum, pale yellow, the surfaces minutely pitted, the testal cells irregularly quadrate in outline. Stone cells (4)6-8, the 2 apical ones 1.5-2 mm in diameter, usually very closely paired, the rest equatorial and 1-1.2 mm in diameter, pale whitish brown. Chromosome number: n = 12 ( Moscone 1992, vouchers Bernardello & Di Fulvio 476, Moscone 99, Subils 3382; one individual from Bernadello & Di Fulvio 476 with n = 18 and chromosomal anomalies with supernumerary bivalents or univalents not segregating).

Distribution

(Fig. 139 ). Solanum pygmaeum is native to central and coastal Argentina (Provs. Buenos Aires, Chaco, Córdoba, Corrientes, Entre Ríos, La Pampa, San Luis, Santa Fé, Santiago del Estero, Tucumán) and Uruguay (Dept. Rocha); it is also adventive in Europe, arriving as seeds through wool shipments but not usually established as permanent populations. A specimen (Gillies s.n., BM) cited in Särkinen et al. (2018) as being from Chile is almost certainly mislabelled and was collected somewhere in Argentina.

Ecology and habitat.

Solanum pygmaeum in South America grows in dry forests and grassland habitats, usually in sandy and clay soils, along railroad tracks and roadsides; from 100 to 1,000 m.

Common names and uses.

None recorded.

Preliminary conservation status

( IUCN 2022). Least Concern [LC]. EOO = 18,428,537 km2 [LC]; AOO = 596 km2 [VU]; calculated on the global range. Solanum pygmaeum is widespread in its native range and is a patch-forming species of open areas and many different habitat types.

Discussion.

Solanum pygmaeum is a plant that spreads by underground stems, often forming dense stands of small straggling plants along roads and in grassy vegetation. It is easy to distinguish by its large flowers (anthers more than 3.5 mm long), narrowly elliptic calyx lobes (1.5-1.8 mm long), and rhizomatous habit. Leaves are quite variable in size, but are usually narrowly elliptic, less often wider in the lower half. It is most similar to S. rhizomatum of the Bolivian Andes but differs from that species in its unbranched (versus forked) inflorescences, larger anthers (those of S. rhizomatum are less than 3.5 mm long) and berries with 15-25 seeds (versus more than 50 seeds in S. rhizomatum ). The two species are not sympatric.

Details of typification of the synonyms of S. pygmaeum can be found in Särkinen et al. (2018); we have still been unable to trace original material of Solanum pygmaeum var. latifolium .

Figures

Figure 137. Solanum pygmaeum A habit B flowering branch C flower D calyx E dissected calyx, adaxial surface F dissected flower G stamen, dorsal view H stamen, ventral view I gynoecium J fruit K seed (A-K Bernardello & DiFulvio 476). Illustration by L. Ribulgo. Previously published in Barboza et al. (2013: 256) and Saerkinen et al. (2018: 130).

Figure 138. Solanum pygmaeum A habit B flowering branch C dissected flower D developing fruits (A-D Chiarini 1341). Photos by F. Chiarini. Previously published in Saerkinen et al. (2018: 131).

Figure 139. Distribution map of Solanum pygmaeum. For adventive distribution, see Saerkinen et al. (2018: 133).