Solanum marmoratum Barboza & S. Knapp, 2020

Knapp, Sandra, Chiarini, Franco, Cantero, Juan J. & Barboza, Gloria E., 2020, The Morelloid clade of Solanum L. (Solanaceae) in Argentina: nomenclatural changes, three new species and an updated key to all taxa, PhytoKeys 164, pp. 33-66 : 33

Solanum marmoratum Barboza & S. Knapp sp. nov. Figs 4 , 5

Diagnosis.

Like Solanum nitidibaccatum Bitter but differing in eglandular, white pubescence, strongly winged stems, fleshy calyx lobes that are spreading in fruit and larger berries; also similar to S. americanum Mill. but differing in strongly winged stems and dark green mature berries marbled with white markings.

Type.

Argentina. La Pampa: Dtto. 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).

Description.

Watery annual herb, 10-100 cm tall, sprawling and somewhat prostrate when very large. Stems strongly winged, the wing to 1 mm side, 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, axillary shoots common. Leaves simple and shallowly toothed, 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 (1)2-3 cm long, internodal and extraaxillary, unbranched, 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, perfect. 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, included within the anther cone or the stigma just beyond, 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 life plants, the surfaces minutely papillate. Fruit a globose berry, 0.8-1.5 cm in diameter, dark green marbled with white at maturity, glabrous, translucent, the pericarp surface thin, shiny; 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; 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, 1-1.1 mm in diameter, found randomly positioned in the berry. Chromosome number: not known.

Distribution

(Figure 6 ). Solanum marmoratum is endemic to Argentina and occurs in the provinces of Catamarca, La Pampa, La Rioja, San Juan and 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 woodlands (Fig. 4A ) and at the edges of arable fields; it usually grows under trees and shrubs with a number of other herbaceous plants such as S. tweedieanum , various species of Asteraceae and grasses. Specimens have been collected from 200 to 1400 m elevation.

Etymology.

The species is named for its distinctive marbled berries (Fig. 4F, G ) that easily distinguish it from the similar tiny-flowered eglandular species S. americanum .

Preliminary conservation status

( IUCN 2019). AOO (84 km2 - EN); EOO (239,336 km2 - LC). Solanum marmoratum is a relatively widespread species, the extent of occurrence suggests is 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 be 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. We suggest a preliminary threat status of Least Concern (LC) to S. marmoratum , but the widespread habitat conversion in central Argentina warrants further studies as to population status across the species’ historical range.

Notes.

Solanum marmoratum has long confused botanists working with Argentinian solanums. In the herbarium at CORD specimens of S. marmoratum collected by P. Steibel in the province of San Luis were the subject of correspondence with A.T. Hunziker over their identification; they were tentatively identified as S. adventitium Polg., a synonym of S. americanum described from adventive material in Hungary ( Särkinen et al. 2018). None of the pre-1970s specimens we have seen were cited in Morton (1976), but Semper s.n. at US (barcode 02837698) was annotated " Solanum dolichopteryx Morton, paratype" by C.V. Morton in 1971. We have not found specimens annotated as other types at US or elsewhere. A.T. Hunziker had kept specimens of this species aside with the herbarium name " Solanum alatocaule", a reference to the strongly winged stems (Fig. 4B, C ) on the folder, but never described it. We collected S. marmoratum in 2013 (Barboza et al. 3668) along with S. tweedieanum , and mistakenly noted the leaves of S. marmoratum as sticky (see Fig. 5 ); 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 distribution.

The flowers of S. marmoratum are among the tiniest in the morelloid solanums (Fig. 4D, E ) rivalled only by the globally distributed S. americanum and S. nitidibaccatum Bitter 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 (Fig. 4G ) are distinct from those of all of these taxa with tiny flowers.

Solanum marmoratum appears to be highly autogamous and is perhaps entirely self-fertilising. The style is completely included within the anther cone (Fig. 4D, E ) and the filaments appear to elongate through anthesis (see. Fig. 4E ) bringing the style further into the cone as the flower ages. 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. Over the course of anthesis the style becomes enclosed in the anther cone (Fig. 4E ), with the anthers as they dehisce leaving 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.

Additional specimens examined

(paratypes). Argentina. Catamarca: Dtto. Santa María, Chiñucán, Sierra de la Aconquija, falda O, Chiñucán, 12 Apr 1948, Reales 1264 (CORD); Dtto. Belén, Yacutula, Mar 1879, Schickendantz 113 (CORD). La Pampa: Dtto. Toay, Reserva Provincial Parque Luro, pasando la laguna Luro, 233 m, 18 Jan 2013, Barboza et al. 3668 (BM, CORD, SI); Dtto. Utracán, Valle de Daza, rumbo a la Laguna El Loro, 10-12 km de la RP 18, 290 m, 8 Feb 2020, Barboza et al. 5073 (BM, CORD); Dtto. Toay, Reserva Parque Luro, ingreso S por ruta 35 desde General Acha, 116 m, 9 Feb 2020, Barboza et al. 5079 (BM, CORD); Bajo Lucero, cruce entre RP 11 y RP 10, 255 m, 9 Feb 2020, Barboza et al. 5094 (BM, CORD); Dtto. Atreucó, sin. loc., Mar 1960, Cano 960 (US); Dtto. Rancul, Chamaicó, 2 Mar 1984, Steibel & Troiani 7960 (CORD); Chamaicó, 2 Mar 1984, Steibel & Troiani 7963 (CORD); Dtto. Atreucó, Laguna Chillhué, 5 Apr 1984, Steibel et al. 8035 (CORD); Dtto. Capital, Barrancas Coloradas, 28 Feb 1991, Steibel 10111 (CORD); Dtto. Toay, Parque Luro, 8 Mar 1991, Steibel 10118 (CORD); Dtto. Capital, El Guanaco, 30 km al N de Santa Rosa, 13 Feb 1977, Troiani 4688 (CORD); Dtto. Atreucó, Laguna Chillhué, 13 Mar 1982, Troiani et al. 6820 (CORD); Dtto. Loventué, Luan Toro, 10 km al W, 10 Feb 1985, Troiani 8564 (CORD). La Rioja: Dtto. Famatina , Ruta 40 [now Ruta Prov. 11] (km 640/641), yendo de Famatina a Tinogasta, 20 Mar 1960, Hunziker et al. 15172 (CORD); Ruta 40 [now Ruta Prov. 11] (km 692), yendo de Famatina a Tinogasta, entre Santa Cruz y el límite con Catamarca, 20 Mar 1960, Hunziker et al. 15206 (CORD,US). San Juan: Dtto. Sarmiento, a 2 km de la estancia El Acequión, desde El Pedernal hacia el enpalme con Ruta provincial 412, por Ruta Prov. 312, 1400 m, 9 Apr 2004, Matesevach 10 C, (CORD). San Luis: Dtto. General Pedernera, Villa Mercedes, Estancia Agropecuaria INTA San Luis, lote 16, bajo, 510 m, 9 Jan 1969, Anderson & Galvani 1511 (CORD); Sierra El Morro, cuenca interior, querencia pisoteada, 1200 m, 27 Dec 1977, Anderson et al. 3427 (CORD); Dtto. Capital, Estancia Las Tres Marías, 30 km al sur de San Luis-Quemado, 700 m, 21 Mar 1979, Anderson et al. 3643 (CORD); Dtto. Chacabuco, Concarán, cerca de 2 km desde Concarán rumbo a Santa Rosa de Conlara, por el camino de tierra (RP 23), 660 m, 24 Feb 2020, Barboza et al. 5130 (BM, CORD); Concarán, cerca de 5.5 km desde Concarán rumbo a Santa Rosa de Conlara, por el camino de tierra (RP 23), 652 m, 24 Feb 2020, Barboza et al. 5136 (BM, CORD); Dtto. Capital, Potrero de los Funes, 2 Apr 1989, Del Vitto & Petenatti 3455 (CORD); Los Puquios, a 200 m del badén sobre el río Los Puquios en la ruta El Volcán-Cruz de Piedra, rumbo a Cruz de Piedra, 21 May 1972, Giordano & Guerreiro 23 (CORD); Dtto. Chacabuco, a ca. 3 km al N de Concarán, rumbo a Santa Rosa, por el viejo camino de tierra, 17 Feb 1989, Hunziker et al. 25335 (CORD); Dtto. Belgrano, Sierra del Gigante (falda O), Desaguadero, inmediaciones de Paso de Tropas, 7 Apr 1944, Ruiz Leal 9191 (CORD); Dtto. Capital, entre Estación Jarilla y Desaguadero., 500 m, 7 Apr 1944, Semper s.n. (BM, US).

Figures

Figure 4. Solanum marmoratum Barboza & S. Knapp A habit (Barboza et al. 5099) B, C details of the winged stems (both at the same scale, B from Barboza et al. 5136, C from Barboza et al. 5073) D inflorescence (Barboza et al. 5136) E flowers, showing the included style and the filaments that elongate with flower age (Barboza et al. 5136) F mature fruits (Barboza et al. 5073) G Detail of berries showing the spreading fleshy calyx in fruit (Barboza et al. 5130). All photographs by S. Knapp.

Figure 5. Solanum marmoratum Barboza & S. Knapp (Barboza et al. 3668, BM [BM 001134643]).

Figure 6. Distribution of Solanum marmoratum Barboza & S. Knapp.