Like Solanum americanum L. but differing in branched inflorescences with flowers spaced along the rachis (not umbellate), rounded calyx lobes that are not reflexed in fruit, style exserted beyond the anther tube for more than 1 mm, stigma globose and capitate, and fruit with the surface not markedly shiny.

Peru: Cajamarca: Prov. Cajabamba, in town of Cajabamba, 7°36'43"S, 78°03'28"W, 2649 m, 9 May 2013 (fl, fr), S. Knapp, T. Särkinen, H.M. Baden, P. Gonzáles & E. Perales 10575 (holotype: USM!; isotypes: BM!, HUT!, CPUN!).

Herb with woody base, 20–50 cm tall, the individual stems to 1 m long and sprawling. Stems terete or somewhat angled with ridges, pubescent with simple uniseriate 1–4-celled trichomes often clustered along the stem angles; new growth densely pubescent with appressed 1–4-celled simple uniseriate trichomes 0.2–0.8 mm long. Sympodial units difoliate, not geminate. Leaves simple, 4.5–12(–15) cm long, 1.8–8 cm wide, ovate to elliptic; adaxial surface sparsely pubescent with more or less appressed 1-4-celled translucent simple uniseriate trichomes, these denser along the veins; abaxial surface more densely pubescent with simple uniseriate trichomes like those of the upper surface; primary veins 5–8 pairs; base acute and decurrent on the petiole; margins entire or occasionally with shallow lobes in the basal third; apex acute; petiole 0.5–2.5(–5) cm long, occasionally narrowly winged, sparsely pubescent with simple uniseriate trichomes like those of the stems and leaves. Inflorescences lateral and intermodal, 1–2.5 cm long, simple or once-branched, with 3–5(9) flowers, sparsely pubescent with appressed 1–2-celled simple uniseriate trichomes; peduncle 0.4–1.6 cm long, if the inflorescence branched then the peduncle rachis 0.4–0.6 cm long; pedicels 0.6–0.7 cm long, ca. 0.3 mm in diameter at the base and apex, straight and spreading, articulated at the base; pedicel scars spaced ca. 1 mm apart. Buds globose, the corolla only exserted from the calyx tube just before anthesis. Flowers 5-merous, all perfect; calyx tube ca. 1 mm long, the lobes 0.5–0.7 mm long with rounded apices, sparsely pubescent with 1–4-celled translucent simple uniseriate trichomes; corolla 5–6 mm in diameter, stellate, white with a yellow central portion near the base, lobed slightly less than halfway to the base, the lobes ca. 1.5 mm long, 2 mm wide, strongly reflexed at anthesis, later spreading, densely pubescent abaxially with 1–4-celled simple uniseriate trichomes, these usually shorter than the trichomes of the stems and leaves; filament tube minute, pubescent with tangled uniseriate trichomes adaxially; free portion of the filaments ca. 1 mm long, pubescent like the tube; anthers ellipsoid, yellow, ca. 1.5 mm long, 0.7–0.8 mm wide; ovary conical, glabrous; style 3–4 mm long, exserted (0.5)1–2 mm beyond the anther cone, densely pubescent with 2–3-celled simple uniseriate trichomes at the base; stigma globose and capitate, minutely papillate, bright green in live plants. Fruit a globose berry, 4–9 mm in diameter, green at maturity or green and turning purplish black when ripe, the surface not markedly shiny, lacking stone cells aggregates; fruiting pedicels 4–7 mm long, ca. 1 mm in diameter at the base, spreading and becoming somewhat more woody in fruit, usually remaining on the plant after fruit drops; fruiting calyx lobes spreading or appressed to the berry, not reflexed. Seeds 35–45 per berry, 1.2–1.5 mm long, 0.9–1 mm wide, flattened-reniform, yellowish, the surfaces minutely pitted, the testal cells pentagonal in outline.

Endemic to Peru in the upper zones of seasonally dry tropical forests or in mid-elevation montane forests, usually above 2,000 m elevation, with only some overlap between the closely related Solanum americanum that occurs from sea level to 2,200 m in elevation; commonly growing in sandy soils in full sun or partial shade in disturbed sites such as landslides and roadsides or cultivated areas, often in moist depressions in otherwise dry areas, associated with Schinus molle L., Aspidosperma polyneuron Müll. Arg., Eriotheca sp., Vachellia macracantha (Humb. & Bonpl.) Seigler & Ebinger, Alnus acuminata Kunth, Solanum probolospermum Bitter, and Calceolaria spp.; (930-)1700–3200(-3735) m in elevation. Based on field and herbarium collections Solanum pseudoamericanum occurs in the Departments of Amazonas, Ancash, Apurímac, Cajamarca, Cusco, La Libertad, and Piura, but based on the modelled habitat suitability map (Fig. 2) it is also likely to also occur in the Departments of Lambayeque, Huánuco, Huancavelica, Ayacucho, Junín, southwestern San Martín, northernmost areas of Lima, and in the Province of Loja in Ecuador.

Flowering January–July, fruiting March–July.

The name Solanum pseudoamericanum refers to the fact the new species greatly resembles Solanum americanum in general form and has been commonly identified under the name of the more common pantropical weed.

The IUCN threat status ofSolanum pseudoamericanum is here considered of least concern (LC) based on the relatively large extent of the species occurrence (c. 159,000 km²), although the actual area of occupancy is small (96 km²). The species grows readily in disturbed sites and combined with the fact that the currently known populations are spread across Peru, it appears to have relatively low threat status despite the generally increasing human pressure and habitat destruction in the Andes.

PERU. Amazonas: Chachapoyas, 8 km along road from Leimebamba to Celendín, between km 417–416, 6°42'48"S, 77°49'05"W, 2634 m, 21 Apr 2013 (fl, fr), T. Särkinen et al. 4624 (USM, BM). Ancash: Pallasca, Puente Chucusvalle over Río Tablachaca, left bank of river (other side of bridge in La Libertad), 8°12'10"S, 77°57'06"W, 2148 m, 11 May 2013 (fl, fr), S. Knapp et al. 10604 (USM, BM); Pallasca, ca. 10 km above Puente Chucusvalle over Río Tablachaca on rd to Pallasca, 8°13'25"S, 77°57'23"W, 2148 m, 11 May 2013 (fl, fr), S. Knapp et al. 10616 (USM, BM); Huaylas, Dist. Pueblo Libre, just beyond Carapampa village, a few km above bridge over Río Santa, 9°06'28"S, 77°48'42"W, 2637 m, 13 May 2013 (fl, fr), S. Knapp et al. 10650 (USM, BM); Huaraz, Huaraz, in city, 9°31'51"S, 77°31'27"W, 3003 m, 15 May 2013 (fl, fr), T. Särkinen et al. 4670 (USM, BM); Carhuaz, on rd from Mancos to Musho, before Puente Apachico, 9°10'35"S, 77°40'31"W, 2886 m, 16 May 2013 (fl, fr), T. Särkinen et al. 4678 (USM, BM); Corongo, km1-3 on rd to Corongo, a side road from Chimbote-Huaraz main rd, 8°41'38"S, 77°53'51"W, 2334 m, 18 May 2013 (fl, fr), T. Särkinen et al. 4686 (USM, BM); Pomabamba, just in the outskirts of Pomabamba on rd leading to Piscobamba, 8°49'27"S, 77°27'12"W, 3008 m, 21 May 2013 (fl, fr), T. Särkinen et al. 4730 (USM, BM); Pomabamba, 2-3km from Pomabamba towards Lucma, 8°51'13"S, 77°26'12"W, 2837 m, 22 May 2013 (fl, fr), T. Särkinen et al. 4737 (USM, BM); Yungay, ribera del Río, 20 Jul 1977, Luna, A., 70 (USM); Carlos F. Fitzcarrald, on rd between Sapcha and San Luis, 9°05'50"S, 77°21'05"W, 3133 m, 24 May 2013 (fl, fr), T. Särkinen et al. 4778 (USM, BM); Carlos F. Fitzcarrald, in San Luis, outskirts of town, 9°05'35"S, 77°19'42"W, 3147 m, 24 May 2013 (fl, fr), T. Särkinen et al. 4780 (USM, BM); Huari, c. 5km from Pomachaca on road to Llamellín, 9°23'05"S, 77°06'59"W, 2605 m, 26 May 2013 (fl, fr), T. Särkinen et al. 4791 (USM, BM); Huari, on rd from Pomachaca to Llamellín, 9°20'24"S, 77°03'22"W, 2571 m, 26 May 2013 (fl, fr), T. Särkinen et al. 4794 (USM, BM). Apurímac: ca. 11 km from Chincheros descending to Río Pampa on Ayacucho-Andahuaylas rd (RN3), 13°31'27"S, 73°46'15"W, 2215 m, 7 Mar 2012 (fl, fr), S. Knapp et al. 10300 (USM, BM); Chincheros, along Río Pampa on Ayacucho-Andahuaylas rd (RN3), ca. 3-4 km from Puente Pampa on Apurímac side, 13°29'26"S, 73°49'32"W, 2028 m, 7 Mar 2012 (fl, fr), S. Knapp et al. 10307 (BM,USM); Abancay, village of Tambo, above Curahuasi, on rd from Abancay to Cusco, Dist. Curahuasi, 13°32'21"S, 72°43'02"W, 2673 m, 10 Mar 2012 (fl, fr), S. Knapp et al. 10351 (USM, BM); Abancay, at turn to Santuario Curahuasi, ca. 17 km above Puente Cunyac over Río Apurímac, road Abancay-Cusco towards Curahuasi, Dist. Curahuasi, 13°32'19"S, 72°29'28"W, 2340 m, 11 Mar 2012 (fl, fr), S. Knapp et al. 10357 (USM, BM). Cajamarca: Cajabamba, in town of Cajabamba, 7°36'43"S, 78°03'28"W, 2649 m, 9 May 2013 (fl, fr), S. Knapp et al. 10575 (USM, BM); Cajamarca, km1244 on rd from Cajamarca to San Marcos, just outskirts of Namora village, 7°12'04"S, 78°19'33"W, 2764 m, 24 Apr 2013 (fl, fr), T. Särkinen et al. 4640 (USM, BM). Cusco: La Convención, Dist. Echarate, Papelpata, Alto Echarate, 12°46'37"S, 72°36'39"W, 931 m, 24 May 2007 (fl, fr), G. Calatayud et al. 4062 (NY); Anta, Mollepata, W of Cusco, 13°30'29"S, 72°33'21"W, 3200 m, 10 Jan 1984 (fl), A.H. Gentry et al. 44135 (MO); La Convención, Santa Teresa, Dist. Santa Teresa, Carretera Santa Teresa-Hidroelectrica, Bosque Seco Secundario, 13°07'21"S, 72°36'31"W, 1700 m, 20 Mar 2004 (fl, fr), I. Huamantupa et al. 4280 (MO); La Convención, Santa Teresa, Dist. Santa Teresa, Carretera Santa Teresa-Hidroelectrica, Bosque Seco Secundario, 13°07'21"S, 72°36'31"W, 1700 m, 20 Mar 2004 (fl, fr), I. Huamantupa et al. 4287 (MO,USM). La Libertad: Santiago de Chuco, ca. 1 km outside Santiago de Chuco on rd from Shorey and Shorey Chico, at stream crossing, 8°08'38"S, 78°11'08"W, 3735 m, 10 May 2013 (fl, fr), S. Knapp et al. 10590 (USM, BM); Santiago de Chuco, 6-8 km below Mollepata on rd to river valley of Río Tablachaca, right side of river, 8°12'03"S, 77°57'11"W, 3735 m, 11 May 2013 (fl, fr), S. Knapp et al. 10599 (USM, BM). Piura: Huancabamba, Porculla, km 38, 5°50'25"S, 79°29'38"W, 5°50'25"S, 79°29'38"W, 1800 m, 8 Apr 1989 (fl, fr), S. Llatas Q. 2348 (NY).

Most of the collections of Solanum pseudoamericanum are the result of our intensive collecting of Solanaceae in Peru in the last two years. We suspect that the paucity of earlier collections may in part be due to the resemblance to the widespread and weedy Solanum americanum that has led to botanists regarding this new species as not worth collecting. Widespread species often harbour cryptic diversity (e.g., Cavers et al. 2013), especially in groups such as the Morelloid clade, where differences between species are relatively small.

Solanum pseudoamericanum can be distinguished from the similar Solanum americanum by the following suite of characters; berries that are matte or somewhat shiny at maturity, versus very shiny in Solanum americanum, styles that are always exerted to approximately equal to the length of the anther cone, versus styles almost included in the anther cone in Solanum americanum, and globose, bright green stigmas, versus white or pale green stigmas that are merely a widening of the style tip in Solanum americanum. Other members of the Morelloid clade in Peru without glandular trichomes which grow sympatrically with Solanum pseudoamericanum differ from it in being larger in growth form reaching up to 2 m in height, having larger, always violet flowers and fruits that are green at maturity (Solanum probolospermum Bitter and Solanum zahlbruckneri Bitter), or being smaller herbs up to 30 cm high with similar sized flowers but fruits orange or yellow in colour (Solanum corymbosum Jacq and Solanum radicans L.f.).