Solanum arenicola Saerkinen & P. Gonzales , PhytoKeys 44: 53. 2015.

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

7. Solanum arenicola Saerkinen & P. Gonzales, PhytoKeys 44: 53. 2015.

Figs 24 , 25

Type.

Peru. Madre de Dios: Prov. Tambopata, in the boat harbor of Infierno, ca. 20 km SW by road from Puerto Maldonado , 12°44'06"S, 69°13'47"W, 186 m, 3 Aug 2014, T. Särkinen & A. Balarezo 4866 (holotype: USM; isotypes: to be distributed to BM, E, F, GHMDD, HOXA, MO, MOL) .

Description.

Herb or vigorous, weak-stemmed shrub 0.2-1.5 m high. Stems slightly angled, sparsely to densely glandular-pubescent with simple, translucent, uniseriate 3-8-celled trichomes 0.8-2 mm long with glandular tips; new growth densely pubescent with spreading glandular trichomes like those of the stem. Sympodial units difoliate, not geminate. Leaves simple, the blades 2.6-13 cm long, 0.8-5 cm wide, ovate to broadly ovate, widest in the lower third, membranous, discolorous; adaxial surface glabrous; abaxial surface paler or tinged with purple, sparsely pubescent with simple uniseriate trichomes like those of the stem restricted to the veins; principal veins 5-7 pairs; base acute to cuneate and decurrent on the petiole; margins variable from entire to undulate to shallowly lobed; apex acute-acuminate; petiole 0.5-5 cm long, sparsely to densely pubescent with glandular trichomes like those of the stems. Inflorescences internodal, unbranched, 2-3.5 cm long, with 3-8(9) flowers, sparsely to densely pubescent with spreading glandular trichomes like those of the stem; peduncle 1-2.4 cm long; pedicels 0.5-0.7 cm long, ca. 0.3 mm in diameter at the base and 0.4 mm at apex, straight and spreading, articulated at the base; pedicel scars unevenly spaced 1-2.5 mm apart. Buds ellipsoid, the corolla strongly exserted from the calyx tube long before anthesis. Flowers 5-merous, cosexual (hermaphroditic). Calyx tube ca. 1 mm long, shallow, the lobes 0.2-0.5 mm long, triangular with acute apices, sparsely to densely pubescent with glandular trichomes like those of the stem. Corolla 0.8-1.2 cm in diameter, stellate, white with a purple-yellow or yellow-green central eye at the base, lobed 2/3 to the base, the lobes ca. 3.5-4 mm long, 1-1.5 mm wide, strongly reflexed at anthesis, later spreading, densely pubescent abaxially with glandular trichomes like those of the stems, glabrous adaxially. Stamens more or less equal; filament tube 1-1.2 mm long; free portion of the filaments slightly unequal in length, the lower two ca. 1.5 mm long, the upper three ca. 1-1.2 mm long, sparsely pubescent with simple uniseriate 1-3-celled trichomes on the side facing the ovary; anthers 3-4 mm long, 0.8-0.9 mm wide at base and 0.5-0.6 mm wide at apex, cylindrical, narrowing towards the apex, yellow, poricidal at the tips, the pores lengthening to slits with age. Ovary ellipsoid, glabrous; style 4-5.7 mm long, straight, long-exserted beyond the anther cone, densely pubescent up to 2/3 of the length with 1-6-celled simple uniseriate trichomes, these longer at the base and becoming gradually shorter towards the middle; stigma clavate, minutely papillate. Fruit a globose berry, 0.35-0.7 cm in diameter, green, turning purplish black when ripe, the pericarp thin, shiny, opaque, glabrous; fruiting pedicels 1-2 cm long, ca. 0.5 mm in diameter at the base, ca. 0.6 mm in diameter at apex, strongly recurved, not persistent; fruiting calyx lobes appressed to the berry, the tips not reflexed. Seeds 35-45 per berry, ca. 0.8 mm long, ca. 0.6 mm wide, flattened-reniform, narrowing towards one end, yellow, the sub-laterally positioned hilum positioned towards the narrower end, the testal cells pentagonal in outline. Stone cells 4 per berry, 0.75-1 mm in diameter, scattered throughout, relatively large compared to the seeds, white or cream-coloured. Chromosome number: not known.

Distribution

(Fig. 26 ). Solanum arenicola occurs in the Amazonian slopes of the Andes in Bolivia (Depts. Beni, La Paz, Pando, Santa Cruz) and Peru (Depts. Cusco, Junín, Madre de Dios, Pasco, Puno). Currently, S. arenicola is known from central and southern Peru and from Bolivia, but it is likely that the species also occurs in adjacent areas of Brazil in the State of Rondônia, where the Río Madre de Dios and Río Beni join and cross into Brazil.

Ecology and habitat.

Solanum arenicola grows on sandbanks and river margins, tree fall gaps, and in disturbed sites near houses and fields in open, sandy soil in lowland moist rain forest, with occasional records from seasonally dry semi-deciduous forests, often associated with lowland rain forest pioneer species; from 0 to 600 (1,300) m elevation.

Common names and uses.

None recorded.

Preliminary conservation status

( IUCN 2022). Least Concern [LC]. EOO = 748,101 km2 [LC]; AOO = 164 km2 [EN]. Solanum arenicola grows in disturbed sites along rivers, tree falls, and cultivations where bare sandy soils are available, and its association with other pioneer species indicates that the species is not sensitive to human disturbance from expanding construction and agriculture. It occurs within protected areas in Peru (Parque Nacional Manu) and Bolivia (Parque Nacional Amboró).

Discussion.

Solanum arenicola is one of the few morelloids known from lowland humid forests in South America. It can be easily distinguished from S. americanum , the only other similar morelloid species found in these habitats in its larger anthers (3-4 mm long versus less than 1.5 mm long) and its glandular pubescence. Specimens without locality information can be easily confused with S. nigrescens of Central and northern South America, S. aloysiifolium of middle to high elevations in Argentina and Bolivia or S. subtusviolaceum of low to middle elevations in Peru and Bolivia. Both S. arenicola and S. nigrescens have unbranched inflorescences, but S. arenicola differs in having longer anthers (3-4 mm long) compared to S. nigrescens (2-2.5 mm long) and in the possession of glandular hairs ( S. nigrescens is eglandular). The anthers are similar in size and shape to those of S. aloysiifolium , but S. arenicola has unbranched inflorescences and glandular pubescence, while S. aloysiifolium has forked inflorescences (sometimes many branched) and is eglandular. Solanum arenicola differs from S. subtusviolaceum in having internodal inflorescences (versus leaf-opposed), much reduced calyx lobes to only 0.5 mm long (versus 2-3.5 mm long), and a more exserted style extending 2-3 mm beyond the anther cone at anthesis (versus 0-0.5 mm).

Figures

Figure 24. Solanum arenicola A flowering and fruiting branch B fruiting branch C stem detail with glandular multi-cellular trichomes D flower bud E flower at full anthesis F dissected flower G infructescence H fruit I seed (A-I Parada & Rojas 2506). Illustration by C. Banks.

Figure 25. Solanum arenicola A habit B buds and flowers, showing the dense glandular pubescence C maturing fruits with reflexed pedicels D leaf size and shape variation within an individual plant (A-D Saerkinen & Balarezo 4866). Photos by T. Saerkinen. Previously published in Saerkinen et al. (2015 c: 54).

Figure 26. Distribution map of Solanum arenicola.