Solanum arenicola Saerkinen & P. Gonzales, 2015

Saerkinen, Tiina, Gonzales, Paul & Knapp, Sandra, 2015, Four new non-spiny Solanum (Solanaceae) species from South America, PhytoKeys 44, pp. 39-64 : 49-51

Solanum arenicola Saerkinen & P. Gonzales sp. nov. Figs 5 -6

Diagnosis.

Like Solanum aloysiifolium Dunal, but differing in having simple, sub-umbellate inflorescences, and a dense indumentum of multicellular glandular-tipped trichomes; also similar to Solanum subtusviolaceum Bitter, but differing in having internodal inflorescences, much reduced calyx lobes to only 0.5 mm long, corolla deeply lobed to 2/3 of the way to the base, and a more exerted style extending 2-3 mm beyond the anther cone at anthesis.

Type.

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

Description.

Herb or vigorous, weak-stemmed shrub 0.2-1.5 m tall. Stems angled, sparsely to densely 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, 2.6-13 cm long, 0.8-5 cm wide, ovate to broadly ovate, membranous; 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; primary veins 5-7 pairs; base acute to cuneate and decurrent on the petiole; margins variable in shape from entire to undulate to shallowly lobed; apex acute-acuminate; petiole 0.5-5.0 cm long, sparsely to densely pubescent with glandular trichomes like those of the stems. Inflorescences 2.0-3.5 cm long, lateral and internodal, simple, with 3-8(9) flowers, sparsely to densely pubescent with spreading glandular trichomes like those of the stem; peduncle 1.0-2.4 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 1.0-2.5 mm apart. Buds ellipsoid, the corolla strongly exerted from the calyx tube long before anthesis. Flowers 5-merous, all perfect; 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 8-12 mm 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. 3.5-4.0 mm long, 1.0-1.5 mm wide, strongly reflexed at anthesis, later spreading, densely pubescent abaxially with glandular trichomes like those of the stems, glabrous adaxially; filament tube 1.0-1.2 mm long; free portion of the filaments slightly unequal in length, the lower two ca. 1.5 mm long, the upper three ca. 1.0-1.2 mm long, sparsely pubescent with simple uniseriate 1-3-celled trichomes on the side facing the ovary; anthers 3.0-4.0 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, exerted 2.0-3.0 mm 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, 3.5-7.0 mm in diameter, green, turning black when ripe; fruiting peduncle 2.0 cm long; fruiting pedicels 1.0-2.0 cm long, ca. 0.5 mm in diameter at the base and 0.6 mm at apex, strongly recurved; 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 few per fruit.

Distribution.

In lowland Bolivia and Peru; in lowland moist rain forest in sandbanks and river margins, tree fall gaps, and in disturbed sites near housing and fields in open, sandy soil, with occasional records from seasonally dry semi-deciduous forests with Hura crepitans L. ( Euphorbiaceae ), Gallesia integrifolia (Spreng.) Harms ( Phytolaccaceae ), Bougainvillea modesta Heimer ( Nyctaginaceae ), and Anadenanthera colubrina (Vell.) Brenan ( Amaranthaceae ); most commonly associated with lowland rain forest pioneer species, including Salix humboldtiana Willd. ( Salicaceae ), Tessaria integrifolia Ruiz & Pav. ( Asteraceae ), Cecropia spp. ( Urticaceae ), Calliandra sp. ( Fabaceae ), Neea spp. ( Nyctaginaceae ), Garcinia spp. ( Clusiaceae ), and Jacaratia digitata (Poepp. & Endl.) Solms ( Caricaceae ), and annual herbs such as Glinus radiatus (Ruiz & Pav.) Rohrb. ( Molluginaceae ), Physalis angulata L., Physalis peruviana L., and Solanum americanum Mill. (Solanceae); 0-600 (1,300) m elevation.

Ecology.

Flowering January-February and August-October, fruiting September-October.

Etymology.

Solanum arenicola is named for its habitat preference as deduced from both field observations and specimen labels. The species prefers growing on sand (cola = "liver on", and arena = “sand”) and is most commonly collected from sand bars, loose sandy soils on land slides, at the base of tree falls on open, loosened sandy soil, or in open-sandy soils in disturbed areas around houses and cultivated plots.

Conservation status.

The preliminary IUCN (2010) conservation status of Solanum arenicola is here considered of least concern (LC) based on the relatively large EOO (c. 412,600 km2), although the small AOO (56 km2) would merit listing with endangered (EN) status. The species 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.

Specimens examined.

BOLIVIA. Beni: Prov. Ballivian, Carmen Florida, Rio Beni, 7 km upstream from Rurrenabaque, 320m, 13 Sep 1989, D.E. Williams 960 (US); La Paz: Prov. Abel Iturralde, Parque Nacional Madidi, laguna Chalalan, Río Yariapo, c. 14°26'41"S, 67°53'05"W, 275m, 26 Sep 2006, A. Araújo-M et al. 3130 (NY); Prov. Franz Tamayo, Tuichi, Río San Juan, Buenahora., 14°12'01"S, 68°39'21"W, 840m, 1 Oct 2005, A. Araújo-M et al. 2071 (BM); Pando: Prov. Manuripi, large sandbar in Río Madre de Dios, 8 km (by air) NNE of Nueva Etea, 11°15'S, 66°57'W, 125m, 22 Aug 1985, M. Nee 31497 (K); Prov. Madre de Dios, Puerto Candelaria, along the Rio Madre de Dios, 21 km (by air) WSW of Riberalta, c. 11°02'00"S, 66°15'00"W, 125m, 18 Aug 1985, M. Nee 31398 (NY); Prov. Manuripi, Conquista, Embarcadero sobre el Madre de Dios, 150m, 2 Feb 1983, J. Fernández Casas 8591 (NY); Along Rio Madre de Dios between Trinidadcito and San Miguel, 50 km (by air) WSW of Riberalta, c. 11°06'S, 66°31'W, 125m, 21 Aug 1985, M. Nee 31483 (NY); Along Rio Madre de Dios, Camacho, 11°32'S, 67°42'W, 135m, 2 Sep 1985, M. Nee 31724 (NY); Santa Cruz: Ichilo: Parque Nacional Amboró, along Rio Saguayo, 0.5 km NE of entrance into first Andean foothills, 1465m, 22 Dec 1988, M. Nee 37350 (MO, US); PERU. Cusco: Prov. Paucartambo, 6 Aug 1974, R.B. Foster et al. 3021 (USM); Junín: Chanchamayo: La Merced, 610m, 10 Aug 1923, J.F. Macbride, 5314 (F); Chanchamayo: Rd from San Ramon past Vitoc to Union Mantish, past Rio Chilpes, 11°15'08"S, 75°21'36"W, 1309m, 2 Jun 2013, T. Särkinen et al. 4831 (USM); Madre de Dios: Prov. Tambopata, Explorer'S, Inn, nr the confluence of Rio Tambopata and Rio La Torre, 39 km SW of Puerto Maldonado, 400m along the Laguna Chica Trail, c. 12°50'S, 69°20'W, 17 Jan 1989, S.F. Smith et al. 1354 (NY).

Discussion.

Solanum arenicola can be easily distinguished from Solanum americanum Mill., the only other similar Morelloid species found in lowland Amazonia; it has larger anthers which are 3.0-3.2 mm long in Solanum arenicola as compared to the minute anthers <1.5 mm of Solanum americanum . Specimens without locality information can be easily confused with Solanum nigrescens M.Martens & Galeotti of Central and northern South America, Solanum aloysiifolium Dunal of middle to high elevation Argentina and Bolivia or Solanum subtusviolaceum Bitter of low to middle elevation Peru and Bolivia. Both Solanum arenicola and Solanum nigrescens have simple inflorescences, but Solanum arenicola differs in having longer anthers (3.0-3.2 mm) compared to Solanum nigrescens (1.5-2.2 mm) and in the possession of glandular hairs ( Solanum nigrescens is eglandular). The anthers are similar in size and shape to those of Solanum aloysiifolium , but Solanum arenicola has simple inflorescences and glandular-tipped hairs, while Solanum aloysiifolium has branched inflorescences (sometimes many branched) and lacks glandular hairs. Solanum subtusviolaceum possesses the same dense, glandular-haired indumentum as Solanum arenicola , but differs from it in having inflorescences with the flowers clustered near the tips positioned opposite the leaves rather than arising along the internodes, longer calyx lobes (2-3 mm versus 0.2-0.5 mm), more rotate corollas lobed only halfway to the base, and less exerted styles (to a maximum of 1 mm versus exerted to 3 mm beyond the anther cone).

Solanum arenicola is one of the few morelloids known from lowland humid forests in South America. Most morelloid species grow> 2,000 m or in drier habitats along the western slope of the Andes or in the inter-Andean valleys, whilst Solanum arenicola is restricted to humid forests on the eastern side of the Andes below 1,200 m elevation. Currently, the species 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 the Brazilian border, especially considering habitat preferences of Solanum arenicola for disturbed, sandy soils along river banks.