Solanum americanum Mill., Gard. Dict. ed. 8, no. 5. 1768.

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

4. Solanum americanum Mill., Gard. Dict. ed. 8, no. 5. 1768.

Figs 15 , 16

Solanum oleraceum Dunal, Encycl. [J. Lamarck & al.] Suppl. 3: 750. 1814. Type. “Antilles” Herb, Richard s.n. (lectotype, designated by D’Arcy 1974a, pg. 735: P [P00319557]; isolectotypes: G-DC [G00144258], MPU [n.v.]).

Solanum erythrocarpon G.Mey., Prim. Fl. Esseq. 109. 1818. Type. Suriname. Saramacca: Hamburg (Essequibo), E.K. Rodschied 31 (lectotype, designated by Särkinen et al. 2018, pg. 52: GOET [GOET003505]).

Solanum nigrum Vell., Fl. Flumin. 85. 1829 [1825], nom. illeg., not Solanum nigrum L. (1753). Type. Brazil. [Rio de Janeiro]: "undequaeque nascitur" (lectotype, designated by Knapp et al. 2015, pg. 832: [illustration] Original parchment plate of Flora Fluminensis in the Manuscript Section of the Biblioteca Nacional, Rio de Janeiro [cat. no.: mss1198651_112] and later published in Vellozo, Fl. Flumin. Icon. 2: tab. 109. 1831).

Solanum tenuiflorum Steud., Nomencl. ed. 2, 2: 606. 1841. Type. Based on (replacement name for) Solanum nigrum Vell.

Solanum indecorum A.Rich., Hist. Fls. Cuba, Fanerogamia 11: 121. 1841. Type. Cuba. Sin loc., 1836, R. de la Sagra s.n. (lectotype, designated by Särkinen et al. 2018, pg. 52: P [P00370899]).

Solanum nigrum L. var. angulosum Sendtn., Fl. Bras. (Martius) 10: 16. 1846, as Solanum nigrum L. subsp. nodiflorum (Jacq.) Sendtn. var. angulosum Sendtn. Type. Based on Solanum tenuiflorum Steud. (= Solanum nigrum Vell.).

Solanum nigrum L. subsp. aguaraquiya Sendtn., Fl. Bras. (Martius) 10: 17. 1846. Type. Brazil. Rio Grande do Sul: "Pat. Joan a St. Barbara", C.F.P. Martius s.n. (lectotype, designated by Särkinen et al. 2018, pg. 52: M [M-0171809]; isolectotype: M [M-0171810]).

Solanum nigrum L. var. minus Hook.f., Trans. Linn. Soc. London 20(2): 201. 1847, as " minor " Type. Ecuador. Galápagos Islands: James Island [Santiago], C. Darwin s.n. (lectotype, designated by Särkinen et al. 2018, pg. 52: CGE [CGE00297]; isolectotype: K [K000922162]).

Solanum amarantoides Dunal, Prodr. [A. P. de Candolle] 13(1): 55. 1852. Type. Brazil. Rio de Janeiro, C. Gaudichaud 522 (lectotype, designated by D’Arcy 1974a, pg. 735 [as holotype]; second step designated by Särkinen et al. 2018, pg. 52: P [P00319574]; isolectotypes: P [P00319575], MPU [n.v.]).

Solanum pterocaulum Dunal var. aguaraquiya (Sendtn.) Dunal, Prodr. [A. P. de Candolle] 13(1): 52. 1852, as ' pterocaulon> '. Type. Based on Solanum nigrum L. subsp. Solanum nigrum aguaraquiya Sendtn.

Solanum ptychanthum Dunal, Prodr. [A. P. de Candolle] 13(1): 54. 1852. Type. United States of America. Georgia: Chatham Co., Savannah, Anon. s.n. (holotype: G-DC [G00144485]).

Solanum nodiflorum Jacq. var. macrophyllum Dunal, Prodr. [A. P. de Candolle] 13(1): 46. 1852. Type. Brazil. Rio de Janeiro: Rio de Janeiro, C. Gaudichaud 521 (lectotype, designated by D’Arcy 1974a, pg. 735: P [P00319582]; isolectotypes: P [P00319583, P00319585], G-DC [G00144100], G [G00343373]).

Solanum nodiflorum Jacq. var. acuminatum Dunal, Prodr. [A. P. de Candolle] 13(1): 46. 1852. Type. Brazil. Minas Gerais: Sin loc., M. Vauthier 537 (lectotype, designated by D’Arcy 1974a, pg. 735 [as type ex Herb. Drake]: P [P00319615]; isolectotypes: P [P00319614], G-DC [G00343360]).

Solanum nodiflorum Jacq. var. petiolastrum Dunal, Prodr. [A. P. de Candolle] 13(1): 46. 1852. Type. Brazil. Rio de Janeiro: Novo Friburgo, 1842, P. Claussen 180 (holotype: P [P00319584]).

Solanum inops Dunal, Prodr. [A. P. de Candolle] 13(1): 55. 1852. Type. Mexico. "sin. loc." [Tamaulipas: Tampico, 4 Feb 1827], J.L. Berlandier 46 (holotype: G-DC [G00144469]; isotypes: BM [BM000775579], F [F0073104F], LE, P [P00336046, P00336047, P00336048], W [acc. # 1889-0291394, acc. # 1889-0144848]).

Solanum nigrum L. var. oleraceum (Dunal) Hitchc., Rep. Missouri Bot. Gard 4: 111. 1893. Type. Based on Solanum oleraceum Dunal.

Solanum nigrum L. var. americanum (Mill.) O.E.Schulz, Symb. Antill. (Urban) 6: 160. 1909. Type. Based on Solanum americanum Mill.

Solanum nigrum L. forma grandifolium O.E.Schulz, Symb. Antill. (Urban) 6: 160. 1909, as Solanum nigrum L. var. americanum (Mill.) O.E.Schulz forma grandiifolia O.E.Schulz. Type. Puerto Rico. "Prope Cayey in sylvis ad rivulum superiorem m. Sept. fl. et. fr.", P.E.E. Sintenis 2429 (no herbarium cited; no duplicates found).

Solanum nigrum L. forma parvifolium O.E.Schulz, Symb. Antill. (Urban) 6: 160. 1909, as Solanum nigrum L. var. americanum (Mill.) O.E.Schulz forma parvifolia O.E.Schulz. Type. Cuba. La Habana: Santiago de las Vegas "Baker Herb. Cub. 3377" (no herbarium cited; no duplicates found).

Solanum minutibaccatum Bitter, Repert. Spec. Nov. Regni Veg. 10: 549. 1912. Type. Bolivia. La Paz: "San Carlos, bei Mapiri", 750 m, Aug 1907, O. Buchtien 1443 (lectotype, designated by Särkinen et al. 2018, pg. 54: US [00027684, acc. # 1175843]; isotypes: GOET [GOET003478], NY [00172089]).

Solanum inconspicuum Bitter, Repert. Spec. Nov. Regni Veg. 11: 204. 1912. Type. Peru. Lima: Lima, 12 Jul 1910, C. Seler 222 (holotype: B, destroyed; no duplicates found).

Solanum tenellum Bitter, Repert. Spec. Nov. Regni Veg. 11: 219. 1912. Type. Brasil. Minas Gerais: "Prope urbem Caldas florens fructibusque instructum", 4 Oct 1869, A.F. Regnell III 970 (holotype: UPS; isotype: US [00027821, acc. # 201069]).

Solanum minutibaccatum Bitter subsp. curtipedunculatum Bitter, Repert. Spec. Nov. Regni Veg. 11: 205. 1912. Type. Bolivia. La Paz: Guanai-Tipuani, Apr-Jun 1892, M. Bang 1462 (holotype: W [acc. # 1893-0005615]; isotypes: BM [BM000617672], E [E00106087], M [M-0171808], MO [MO-503647, acc. # 1713464], NDG [NDG42278], NY [00172090, 00172091, 00172092], PH [00030453], US [00027685, acc. # 1324656; 02835359], WIS [0256198WIS]).

Solanum sciaphilum Bitter, Repert. Spec. Nov. Regni Veg. 11: 220. 1912. Type. Brazil. Santa Catarina: Pedras Grandes, Aug 1890, E. Ule 1678 (holotype: B, destroyed [F neg. 2851]; lectotype, designated by Särkinen et al. 2018, pg. 54: HBG [HBG-511539]; isolectotype: HBG [HBG-511540]).

Solanum curtipes Bitter, Repert. Spec. Nov. Regni Veg. 11: 228. 1912. Type. Paraguay. Cordillera: San Bernardino, Aug 1898-1899, É. Hassler 3104 (holotype: B, destroyed; lectotype, designated by Morton 1976, pg. 149: G [G00306710]; isolectotypes: G [G00306711, G00306712, G00306713, G00306714], K [K000532497], P [P00325762], NY [00139112], UC [UC950837]).

Solanum calvum Bitter, Repert. Spec. Nov. Regni Veg. 12: 81. 1913. Type. Mexico. Baja California: Guadalupe Island, 1875, E. Palmer 60 [pro parte] (holotype: UPS; isotypes: BM [BM001017192], MO [MO-159620, acc. # 5257812; MO-568722, acc. # 1713454], NY [00138967, 00759880], YU [YU065319]).

Solanum nodiflorum Jacq. var. sapucayense Chodat, Bull. Soc. Bot. Genève, sér. 2, 8: 150. 1916. Type. Paraguay. Paraguarí: Sapucaí [ “Sapucay”], 1914, R. Chodat & W. Vischer 46 (holotype: G [G00306708]).

Type.

Cultivated at the Chelsea Physic Garden [in protologue said to "grow naturally in Virginia"], Herb. Miller s.n. (lectotype, designated by Edmonds 1972, pg. 103 [as type]: BM [BM000617683]).

Description.

Annual to short-lived perennial herbs up to 1.5 m high, subwoody at base. Stems terete or somewhat angled with ridges, older stems sometimes with spinose processes, not markedly hollow; new growth pubescent with simple, spreading, uniseriate 2-8-celled eglandular trichomes 0.2-0.8 mm long, often clustered along the stem angles; older stems glabrescent. Sympodial units difoliate, the leaves not geminate. Leaves simple, the blades 3.5-10.5 cm long, 1-4.5 cm wide, ovate to elliptic, widest at the middle or in the lower third, membranous, concolorous or slightly discolorous; adaxial surface sparsely pubescent with simple, uniseriate trichomes like those on stem, these evenly spread along the lamina and the veins; abaxial surface similar but more densely pubescent; major veins 3-6 pairs; base attenuate, decurrent on the petiole; margins entire or occasionally sinuate-dentate; apex acute; petioles (0.3-)2-3.8(-4) cm long, sparsely pubescent with simple uniseriate trichomes like those on stems. Inflorescences internodal, unbranched or extremely rarely forked, 0.6-2.5 cm long, with (3-)4-6(8) flowers (outside of South America very rarely with many flowers in unusual many-branched inflorescences) clustered near the tips (umbelliform to sub-umbelliform), sparsely pubescent with simple uniseriate trichomes like those on stems; peduncle (0.5-)1-1.8 cm long, delicate; pedicels 3-9 mm long, 0.2-0.3 mm in diameter at the base and 0.4-0.5 mm at the apex, stout, straight and spreading, articulated at the base; pedicel scars spaced 0-0.5 mm apart, clustered at the tip of the inflorescence. Buds broadly ellipsoid, the corolla exserted 1/3 beyond the calyx lobe tips before anthesis. Flowers 5-merous, cosexual (hermaphroditic). Calyx tube 0.8-1.3 mm long, the lobes 0.3-0.5 mm long, 0.5-0.6 mm wide, broadly triangular with obtuse apices, sparsely pubescent with simple uniseriate trichomes like those of the stem. Corolla 0.3-0.6 cm in diameter, stellate, white with a yellow-green central portion near the base, lobed halfway to 2/3 of the way to the base, the lobes 2-3.2 mm long, 1-2.5 mm wide, strongly reflexed at anthesis, later spreading, densely papillate abaxially with 1-4-celled simple uniseriate trichomes, these denser on the tips and margins. Stamens equal; filament tube minute; free portion of the filaments 0.5-0.8 mm long, adaxially pubescent with tangled uniseriate trichomes; anthers 0.7-1.5 mm long, 0.5-0.6 mm wide, ellipsoid to almost globose and very plump-looking, yellow, poricidal at the tips, the pores lengthening to slits with age and drying. Ovary globose, glabrous; style 2.2-2.6 mm long, straight, almost included to exserted beyond the anther cone, densely pubescent with 2-3-celled simple uniseriate trichomes 2/3 from the base where included in the anther cone; stigma minutely capitate, the surface minutely papillate, green in live plants. Fruit a globose berry, 0.4-0.9(-1.2) cm in diameter, purplish-black at maturity, the surface of the pericarp markedly shiny, opaque, glabrous; fruiting pedicels 1.3-1.8 cm long, ca. 0.7-1 mm in diameter at the base, 0.8-1 mm in diameter at the apex, stout, straight and spreading, spaced ca. 1(-3) mm apart or tightly clustered, persistent, remaining on the plant and persistent on older inflorescences; fruiting calyx lobes not accrescent, the tube less than 1 mm long, the lobes 1(-2) mm long, strongly reflexed at fruit maturity. Seeds 30-50 per berry, 1-1.5 mm long, 0.8-1.3 mm wide, flattened and teardrop shaped with a subapical hilum, pale yellow, the surfaces minutely pitted, the testal cells pentagonal in outline. Stone cells mostly absent (Australia, South Pacific, and South America), but if present (North America, Mexico, Caribbean, Eurasia and Africa) 2-4(6) per berry, 2-4 larger ones> 0.5 mm, and two smaller ones <0.5 mm in diameter. Chromosome number: n = 12 (see Särkinen et al. 2018 for vouchers).

Distribution

(Fig. 17 ). Solanum americanum is a globally distributed weed found throughout the tropics and subtropics; it is not clear where it is native, or if this circumtropical distribution is its native range. In South America it occurs in every country and as far south as 37°S latitude.

Ecology and habitat.

Solanum americanum is a weedy species that colonises disturbed soil and it is found in open areas, along roads, treefall gaps and at the back of beaches from sea level to 2,000 m elevation.

Common names and uses.

Argentina. Misiones: ka’a ete’I ( Mbyá Guaraní, Keller 2007). Paraguay. Arachichu ( Ibarrola and Degen 2011). Brazil. araxixu, caraxixá, erva-de-bicho, erva-mocó, erva-moura, guaraquinha, maria-preta, maria-pretinha, pimenta de cachorro, pimento de rato, pimenta de rato (Lorenzi and Abreu Matos 2002, could also refer to S. paucidens ); caraxixá, erva moura, guaraquinha, maria-pretinha, pimento de galinha ( Ferreira Kinupp and Lorenzi 2021); Pernambuco: erva moura ( Rodrigues and Andrade 2014).

In Argentina, fruits are used as compresses and poultices to treat boils ( Kujawska and Hilgert 2014), and in both Paraguay and Argentina the fruits and leaves have been reported as used medicinally ( Keller 2007; Ibarrola and Degen 2011). In rural communities of Pernambuco, Brazil, macerated leaves are used to treat fungal infections, gastritis, varicose veins and bruises ( Rodrigues and Andrade 2014). Uses reported in Lorenzi and Abreu Matos (2002) are discussed in the section on uses.

Across its range in South America S. americanum is often known by the common name yerba (hierba) mora (Spanish) or erva-moura (Portuguese). In Mexico (see Knapp et al. 2019) and outside the Americas (see Särkinen et al. 2018) the leaves are eaten as cooked greens (potherbs) but we have seen no records of these uses of S. americanum from South America.

Preliminary conservation status

( IUCN 2022). Least Concern [LC]. EOO = 89,639,763 km2 [LC]; AOO = 9,828km2 [LC]. Solanum americanum is a cosmopolitan weed of the tropics and subtropics (see Särkinen et al. 2018; Knapp et al. 2019).

Discussion.

Solanum americanum is the most widespread and common species of the morelloid solanums (see Särkinen et al. 2018), and quite possibly the most widely distributed species in Solanum . It has been implicated as the diploid parent in the polyploid events that gave rise to the species occurring outside of the Americas (e.g., Edmonds 1977; Poczai and Hyvönen 2011), although this has been disputed ( Ma 1995)

Solanum americanum can be easily recognised in fruit by its shiny black berries with small, strongly reflexed calyx lobes that are held on erect or spreading pedicels. In flower, the species has tiny almost globose anthers 0.8-1.5 mm long and short filaments usually less than 1 mm long. Ripe berries of S. americanum are shiny black (but that can be difficult to see in herbarium specimens) and in South America lack stone cells; in North and Central America and the Caribbean berries usually have four stone cells in each. When berries ripen in S. americanum they fall from the plant leaving the stout, spreading pedicels with reflexed calyces behind.

Solanum nigrescens differs from S. americanum in having larger anthers always more than 2 mm long, matte black or green fruits that are held on spreading or deflexed pedicels that drop with the berry, and calyx lobes appressed to the berry in fruit. Berries of S. nigrescens have more than 5 (usually 5-6 large and several smaller) stone cells, while plants of S. americanum from South America usually lack stone cells. Inflorescences of S. americanum tend to be more sub-umbelliform in appearance than those of S. nigrescens , and calyx lobes of S. americanum are strongly reflexed and smaller relative to berry size in fruit.

Manoko et al. (2007) distinguished S. americanum and S. nodiflorum using AFLP markers; we re-examined the material they used and consider the plants they called S. nodiflorum to be S. americanum as defined here, and plants they called S. americanum represent specimens of S. nigrescens (see Särkinen et al. 2018: 61).

Populations from Río Pastaza, Río Morone, and Río Nanay watersheds in Amazonian Ecuador and Peru have anthers ca. 2 mm long and somewhat more elongate inflorescences than in the rest of the species range. The plants fit well within the circumscription of S. americanum however, with shiny black fruits with reflexed calyx lobes. Variation in pedicel spacing is observed in other parts of the species range, but the larger anther size is unique to these populations in lowland Ecuador and Peru.

Typification details for the many synonyms of S. americanum can be found in Särkinen et al. (2018).

Figures

Figure 15. Solanum americanum A habit B detail of abaxial leaf surface C detail of adaxial leaf surface D branch with inflorescence E leaf F dissected flower G fruit (A-D, F, G Cremers 8084 E Farrugia et al. 2773). Illustration by R. Wise. Previously published in Saerkinen et al. (2018: 57) and Knapp et al. (2019: 38).

Figure 16. Solanum americanum A habit B leaves and young inflorescence C buds and flowers D mature, shiny black fruits with reflexed calyx lobes (A, D Knapp et al. 10210 B Knapp et al. 10205 C Knapp et al. 10360). Photos by S. Knapp. Previously published in Saerkinen et al. (2018: 58) and Knapp et al. (2019: 39).

Figure 17. Distribution map of Solanum americanum in South America. For distribution elsewhere, see Saerkinen et al. (2018: 60) and Knapp et al. (2019: 43).