Solanum tripartitum Dunal, Prodr. [A. P. de Candolle] 13 (1): 72. 1852.

58. Solanum tripartitum Dunal, Prodr. [A. P. de Candolle] 13(1): 72. 1852. Figs 4A, 175, 176 Solanum quadripartitum Dunal, Prodr. [A. P. de Candolle] 13(1): 72. 1852. Type. Bolivia. Circa Miraflor, A.D.'Orbigny 1346 (holotype: P [P00369233]; isotype: MPU [MPU830309]). Type. Bolivia. La Paz: La Paz, 1842, A. D’Orbigny 1537 (lectotype, designated by Barboza et al. 2013, pg. 261: P [P00445317]; isolectotypes: BR [BR0000005570737], G [G00343534], P [P00445318, P00445319], W [acc. # 1889-127572]). Description. Erect to spreading or decumbent perennial herbs or subshrubs, occasionally prostrate, if erect to 1.2 m high with several branches, the stems generally not rooting even where in contact with the soil, but sometimes rooting at the lowermost nodes. Stems terete or with small angles from the decurrent leaf bases, completely glabrous to sparsely pubescent with simple uniseriate eglandular trichomes to 0.4 mm long from the ciliate lower margin of the petiole; new growth glabrous or moderately pubescent with simple uniseriate eglandular trichomes to 0.4 mm long, these denser near the stems; bark of older stems pale greenish grey. Sympodial units difoliate, the leaves not geminate. Leaves deeply lobed or occasionally simple, the blades (2.5)3.5-11 cm long, (2.5)3-8 cm wide, broadly elliptic to ovate, widest at the middle or in the lower half, membranous to chartaceous, concolorous; adaxially and abaxially glabrous; principal veins 2(-4) pairs, the terminal leaf lobe with an additional 2-4 pairs of veins; base long-attenuate; margins occasionally entire (some populations in Salta, Argentina), more often lobed nearly to the midrib, the lobes usually 3, occasionally 5, rarely one of the lateral lobes with minute secondary lobes, the terminal lobe lanceolate, the lateral lobes asymmetrically lanceolate with more laminar tissue basiscopically, all narrower at the base and widest at the middle, the lobe tips acute; apex acute to slightly rounded; petioles 0.5-1.5 cm long, 1/10 to 1/5 the length of the blades, winged to the base, glabrous or sometimes sparsely ciliate with simple uniseriate trichomes near the base. Inflorescences extra-axillary, often just above the bifurcation of a stem, forked or many-branched, (1.5-) 2-4(-7) cm long, with 5-10 flowers per branch, glabrous or rarely minutely puberulent; peduncle 0.5-1 (-1.2) cm; pedicels 2-5 mm long, occasionally slightly angled at the apex from the base of the calyx, deflexed and nodding at anthesis, articulated at the base; pedicel scars irregularly spaced 2-4 mm apart. Buds elliptic to obelliptic, the corolla strongly exserted from the calyx tube before anthesis, buds purple-tinged to dark purple. Flowers 5-merous, cosexual (hermaphroditic). Calyx tube 1-1.5 mm long, cup-shaped and abruptly narrowing to the pedicel, the lobes 0.5-1.2 mm long, 0.6-1 mm wide, triangular with obtuse to acute tips, glabrous or rarely minutely puberulent, the sinuses somewhat scarious. Corolla 0.9-1.1 cm in diameter, shallowly stellate, white, violet or light violet, with a pale green or yellowish green central eye, lobed ca. halfway to the base, the lobes 2-3.5 mm long, 2-3 mm wide, broadly triangular, spreading, adaxially glabrous, abaxially minutely white-puberulent at least on the tips. Stamens equal; filament tube minute; free portion of the filaments 0.2-0.6 mm long, pubescent with tangled simple uniseriate trichomes abaxially; anthers 1.8-2.3 mm long, 0.5-0.9 mm wide, elliptic-oblong and wider in the distal third, somewhat connivent, yellow, poricidal at the tips, the pores lengthening to slits with age. Ovary conical, glabrous; style 3-5 mm long, straight, exserted beyond the anther cone, glabrous or minutely puberulent near the base; stigma capitate, the surfaces minutely papillate, pale green in live plants. Fruit a depressed-globose, flattened berry, 0.6-0.7 cm in diameter, markedly bilobed when immature, nearly globose when ripe, passing from green to orange to red when fully ripe, the pericarp thin, shiny, opaque, glabrous; fruiting pedicels 0.7-0.8 cm long, ca. 0.5 mm in diameter at the base, ca. 1 mm in diameter at the apex, strongly recurved at the base to hold the fruit downwards, but always well above the soil level, not persistent; fruiting calyx not accrescent, appressed to the berry surface or the tips slightly reflexed, not enlarging from size in flower. Seeds ca. 40 per berry, 1.4-2 mm long, 1.3-1.5 mm wide, flattened-reniform, light yellow or pale tan-brown, the surfaces minutely pitted, the testal cells sinuate in outline. Stone cells 2(-6) per berry, 2 of these apically positioned and 2-2.2 mm in diameter, occasionally with 1-4 additional smaller stone cells ca. 0.5 mm in diameter scatted throughout berry, all pale cream. Chromosome number: 2n = 24 (Acosta et al. 2005, voucher Hunziker et al. 24745). Distribution (Fig. 177). Solanum tripartitum is known from northern Argentina (Provs. Jujuy, Salta) and Bolivia (Depts. Chuquisaca, Cochabamba, La Paz, Oruro, Potosí, Santa Cruz, Tarija). Ecology and habitat. Solanum tripartitum occurs on steep stony hillsides with low, rather poor vegetation with scattered shrubs and along roadsides in gravelly areas and in association with disturbed ground near habitations, from 600 to 4,270 m elevation. Common names and uses. Argentina. Jujuy: mora mora (Giberti et al. s.n., Arenas et al. 822, Claren 11548), ñusco (Burkart et al. s.n., Claren 11730, Ambrosetti 38, Budin s.n., Hunziker 1290), tomatillo (Biloni 6555). Bolivia. Chuquisaca: ñuschuchu (Barboza 84 bis). In Argentina (Prov. Jujuy) the entire plant (excluding the root) is used medicinally (Hurrel 1991; Lupo and Echenique 1997); the flowers are also reported to be ornamental (Lupo and Echenique 1997). Preliminary conservation status (IUCN 2022). Least Concern [LC]. EOO = 410,690 km2 [LC]; AOO = 564 km2 [EN]. Solanum tripartitum is a weedy plant of open areas and has a wide distribution. It has been collected in protected areas in Argentina (e.g., Humahuaca World Heritage site) and in the area of Parque Nacional Carrasco in Bolivia. Discussion. Solanum tripartitum is a member of the Radicans clade (Särkinen et al. 2015b), together with S. corymbosum, S. palitans and S. radicans. It is largely sympatric with and often is found growing with S. palitans in the same sort of weedy habitats. Michael Nee (pers. comm.) has suggested they hybridise in Bolivia (see discussion of S. palitans). Both taxa have deeply lobed leaves with mostly three leaflets, although S. tripartitum occasionally has five leaflets. Poorly prepared herbarium specimens and those in young flowering condition can be difficult to identify; mixed collections are common. In the field the two species are distinct, with S. tripartitum being an upright plant, the base often decumbent but not rooting, and with erect and branched inflorescences and red ripe berries, while S. palitans is a prostrate plant, rooting at the nodes, and with the simple inflorescences holding the yellow-orange berries at the surface of the soil. Variation in leaf and inflorescence morphology is very local in S. tripartitum. In the Department of Potosí (Bolivia) leaflets are very narrow and the inflorescences are usually many times branched, and in the area of Salta (Argentina) a population is often collected that has undivided leaves (e.g., Varela & del Castillo 1332; Fig. 175B). In other parts of the range the basal-most divisions of leaves of S. tripartitum are occasionally further divided into secondary lobes.Published as part of Knapp, Sandra, Saerkinen, Tiina & Barboza, Gloria E., 2023, A revision of the South American species of the Morelloid clade (Solanum L., Solanaceae), pp. 1-342 in PhytoKeys 231 on page 1, DOI: 10.3897/phytokeys.231.10089