Solanum marmoratum Barboza & S.Knapp, PhytoKeys 164: 46. 2020.

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

31. Solanum marmoratum Barboza & S.Knapp, PhytoKeys 164: 46. 2020.

Figs 95 , 96

Type.

Argentina. La Pampa: Dpto. Loventué, 10 km al W de Luan Toro, rumbo a Loventué, 297 m, 9 Feb 2020, G.E. Barboza, S. Knapp, F. Chiarini & R. Fortunato 5099 (holotype: CORD [CORD00007007]; isotypes: BAB, BM [to be distributed]) .

Description.

Watery annual herbs, 0.1-1 m high, sprawling and somewhat prostrate when large. Stems strongly winged, the wing to 1 mm wide, sometimes with spinose processes (old trichome bases), sparsely to moderately pubescent with spreading to appressed eglandular simple 5-8-celled uniseriate trichomes 0.5-1 mm long, these drying white; new growth densely pubescent with eglandular, white simple uniseriate trichomes 0.5-1 mm long; older stems greenish white, not woody. Sympodial units difoliate, the leaves not geminate. Leaves simple and shallowly toothed, the blades 2-10 cm long, 1.5-6 cm wide, much larger in older plants, ovate, widest in the lower third, membranous, watery and somewhat succulent, concolorous, very bright green on live plants; adaxial and abaxial surfaces evenly white-pubescent with eglandular simple 5-8-celled uniseriate trichomes 0.5-1 mm long, these longer and denser on the veins; principal veins 5-6 pairs; base attenuate onto the petiole; margins shallowly and irregularly toothed, the teeth 2-4 mm long, 2.4- mm wide, broadly deltate, with blunt tips; apex acute; petioles 0.5-2.5 cm long, somewhat winged from the attenuate leaf base, pubescent with simple uniseriate trichomes like the stems and leaves. Inflorescences internodal, unbranched, (1)2-3 cm long, with 5-7 flowers clustered at the tip, usually only 1-2 open at a time, sparsely and evenly pubescent with antrorse simple uniseriate trichomes 0.5-1 mm long like the stems and leaves; peduncle 1.4-2.5 cm long; pedicels 0.4 cm long, ca. 0.5 mm in diameter at the base, ca. 0.6 mm in diameter at the apex, slightly tapering, spreading, eglandular pubescent like the rest of the inflorescence, articulated at the base; pedicel scars tightly packed at the tip of the inflorescence, 0.5-1.5 mm apart. Buds broadly ellipsoid, the corolla included in the calyx tube until just before anthesis. Flowers 5-merous, cosexual (hermaphroditic). Calyx tube 1.2-1.5 mm long, cup-shaped, the lobes 1-1.5 mm, narrowly deltate-triangular, fleshy and recurved in live plants, sparsely pubescent with eglandular white trichomes on both surfaces like the rest of the plant. Corolla 0.5-0.8 cm in diameter, white with a green central star, stellate, lobed ca. halfway to the base, the lobes ca. 2.5 mm long, ca. 2 mm wide, spreading to slightly reflexed at anthesis (flowers closing daily and lasting for several days), adaxially glabrous, abaxially densely pubescent with tiny simple uniseriate trichomes especially at the tips. Stamens equal or slightly unequal with one anther marginally longer than the rest; filament tube ca. 0.1 mm long; free portion of the filaments 0.5-1 mm long, elongating through anthesis, with a few tangled transparent simple uniseriate trichomes adaxially; anthers 1-1.5 mm long 0.6-1 mm wide, ellipsoid, yellow, poricidal at the tips, the pores elongating with age. Ovary conical, glabrous; style 2-2.5 mm, straight, included within the anther cone or the stigma just visible, densely papillate in the lower 3/4; stigma large capitate, held at the level of the anthers when flowers first open, later included within the anther cone, bright green in live plants, the surfaces minutely papillate. Fruit a globose berry, 0.8-1.5 cm in diameter, dark green marbled with white at maturity, the pericarp surface thin, shiny, translucent, glabrous; fruiting pedicels 1.2-1.5 cm long, ca. 1 mm in diameter at the base, ca. 1.5 mm in diameter at the apex, fleshy and watery, tapering to the spreading calyx, strongly deflexed at maturity, with a distinct bend at the pedicel base, not persistent; fruiting calyx somewhat expanded, the tube 3-4 mm long, the lobes 4-5 mm long, ca. 3 mm wide, spreading and fleshy, the tips rounded. Seeds 50-70 per berry, ca. 2 mm long, ca. 1.7 mm wide, flattened teardrop shape with an apical hilum, pale tan to reddish brown, the surfaces minutely pitted, the testal cells mostly rectangular to pentagonal in outline, more sinuate towards the seed centre. Stone cells 1-2 per berry, 1-1.1 mm in diameter, randomly positioned in the berry. Chromosome number: not known.

Distribution

(Fig. 97 ). Solanum marmoratum is endemic to Argentina (Provs. Catamarca, La Pampa, La Rioja, San Luis); we expect it also to be found in Mendoza, because several collections are known from Desaguadero (San Luis), a locality very close to the provincial border that crosses through uniform habitat.

Ecology and habitat.

Solanum marmoratum is found in shady areas in Prosopis ( Leguminosae ) woodlands and at the edges of arable fields; it usually grows under trees and shrubs with a number of other herbaceous plants, from 200 to 1,400 m elevation.

Common names and uses.

None recorded.

Preliminary conservation status

( IUCN 2022). Least Concern [LC]. EOO = 266,502 km2 [LC]; AOO = 100 km2 [EN]. Solanum marmoratum is a relatively widespread species; the extent of occurrence suggests it should be given a status of least concern. The small area of occupancy perhaps reflects a lack of collecting in the dry forest and partially degraded habitats where S. marmoratum occurs. The number of localities (ca. 9) is probably an underestimate due to the widespread perception that these habitats are not interesting; most collections are quite old, and the species has not been collected recently (except by us). The large-scale conversion of land in the range of S. marmoratum to intensive monoculture of commercial crops such as maize, peanuts and sunflowers poses a risk for this and other species in these habitats; use of herbicides and elimination of patches of forest leave little room for even weedy species to persist. Widespread habitat conversion in central Argentina warrants further studies as to population status across the species’ historical range.

Discussion.

Solanum marmoratum had long confused botanists working with Argentinian solanums (see discussion in Knapp et al. 2020). We collected S. marmoratum in 2013 (Barboza et al. 3668) along with S. tweedieanum , and mistakenly noted the leaves of S. marmoratum as sticky; it was only examination of the dried specimens that alerted us to our error. Careful examination of all morelloid collections at CORD in early 2020 showed the distinctness of S. marmoratum and its relatively widespread but fragmented distribution.

The flowers of S. marmoratum are among the tiniest in the morelloid solanums rivalled only by the globally distributed S. americanum and S. nitidibaccatum and the North American S. emulans Raf. (see Knapp et al. 2019). Solanum nitidibaccatum also has somewhat marbled berries but is always extremely sticky and covered with glandular trichomes, in contrast to the eglandular pubescence of S. marmoratum . Solanum americanum and S. emulans both have eglandular pubescence but have purplish black rather than green marbled berries. The fleshy spreading calyx lobes of S. marmoratum are distinct from those of all of these species with tiny flowers.

Solanum marmoratum appears to be highly autogamous and is perhaps entirely self-fertilising. Flowers stay open for several days (closing at night) and in cultivation the plant goes from bud to flower to fruit in 15-18 days with all flowers setting fruit (SK and GEB, pers. obs.). Over the course of anthesis the filaments elongate until the style becomes enclosed in the anther cone (Fig. 96E ); as the anthers dehisce they leave pollen directly on the stigma. Ripe berries last more than two weeks after being gathered from desiccated plants, remaining unchanged as to colour or odour (G.E. Barboza, pers. obs.).

Figures

Figure 95. Solanum marmoratum A habit, vegetative branch B inflorescence C flower at late anthesis D flower opened to show position of style at late anthesis E fruits (A-E Barboza et al. 5099). Illustration by L. Ribulgo.

Figure 96. Solanum marmoratum A habit B, C details of the winged stems D inflorescence E flowers, showing the included style and the filaments that elongate with flower age F mature fruits G detail of berries showing the spreading fleshy calyx in fruit (A Barboza et al. 5099 B, E Barboza et al. 5136 C, F Barboza et al. 5073). Photos by S. Knapp. Previously published in Knapp et al. (2020: 47).

Figure 97. Distribution map of Solanum marmoratum.