Two new non-spiny Solanum species from the Bolivian Andes (Morelloid Clade)

Abstract Two new Bolivian species are described from the Morelloid clade of Solanum (section Solanum in the traditional sense). Solanum alliariifolium M.Nee & Särkinen, sp. nov. is found in montane forests between 1,900 and 3,200 m and is morphologically most similar to Solanum leptocaulon Van Heurck & Müll.Arg., also from montane forests in southern Peru and Bolivia. Solanum rhizomatum Särkinen & M.Nee, sp. nov. is found in seasonally dry forests and matorral vegetation in lower elevations between 1,300 and 2,900 m and is most similar to Solanum pygmaeum Cav., a species native to sub-tropical Argentina but introduced in subtropical and temperate areas worldwide.


Introduction
Solanum is one of the most species-rich vascular plant genera in the tropical Andes (Jørgensen et al. 2011), where many new species continue to be described (e.g., Anderson et al. 2006;Stern and Bohs 2010;Knapp 2010a,b;Farrugia and Bohs 2010;Tepe et al. 2012;Särkinen et al. 2013a;Särkinen et al. 2015). Here we describe two new Solanum species from Bolivia that belong to the Morelloid clade, one of major clades of non-spiny solanums (Weese and Bohs 2007;Särkinen et al. 2013b).
Th e Morelloid clade is a group of ca. 75 species, most of which are endemic to the tropical Andes (Bohs 2005;Särkinen et al. in review). Th e clade includes fi ve major groups (traditionally recognised as sections Solanum, Campanulisolanum Bitter, Parasolanum A.Child, Chamasarachidium Bitter, and Episarcophyllum Bitter), which are in the process of re-circumscription based on molecular results (Särkinen et al. in review). Section Solanum is the largest of these with ca. 52 species and ca. 580 published names and is the only group to occur outside of the Americas. Th e Morelloid clade is distinguished by its herbaceous or sub-shrubby habit, usually internodal infl orescences, small fl owers and fruits, and the usual possession of stone cells in the fruits (Bitter 1911). Th ese are sclerifi ed structures that are usually white and spherical rather than fl attened and brown or yellowish brown like the seeds. Although some studies have examined the taxonomy of the Old World and North American species of this group (Edmonds 1977(Edmonds , 1978Schilling 1981), monographic treatment is needed to aid species identifi cation and to clarify synonymy in South America, where most of the species diversity is found (Edmonds 1972;Barboza et al. 2013).
Recent taxonomic work focusing on producing a monographic treatment of the Morelloid clade has resulted in the description of various new species from Peru, Bolivia and Ecuador (Särkinen et al. 2013a;Särkinen et al. 2015). Two additional new species are described here from Bolivia. Descriptions are based on fi eld work and examination of herbarium specimens from 20 herbaria (BH, BM, COL, CORD, CPUN, DUKE, E, F, GH, GOET, HUSA, HUT, K, LPB, MO, MOL, NY, S, UDBC, US, USM, USZ). Extent of Occurrence (EOO) and Area of Occupancy (AOO) were calculated using GeoCat (www.geocat.kew.org) with a 2 km 2 cell size for AOO calculation. Conservation status of each species was assessed using the IUCN (2014) criteria based on the GeoCat analyses (Bachman et al. 2011) combined with fi eld knowledge. All specimens are cited in the text, and full data is provided in the Suppl. material 1 and on Solanaceae Source (www.solanaceaesource.org). Description. Slender herb to 20-30 cm high, with multiple long, creeping stems arising from a central taproot. Stems rooting at nodes, 1-2 mm in diameter, up to 50 cm long, glabrous or sparsely pubescent with spreading translucent 4-6-celled simple uniseriate trichomes ca. 0.2 mm long. Sympodial units difoliate, not geminate. Leaves simple, 1.5-3.6 cm long, 0.9-2.3 cm wide, broadly ovate to orbicular; adaxial surface glabrous; abaxial surface glabrous or sparely pubescent with appressed 1-3-celled simple uniseriate trichomes along veins and leaf margins; primary veins 3-4 pairs; base rounded to attenuate, occasionally decurrent; margins entire, undulate, or shallowly lobed; apex acute; petiole 0.7-1.5 cm long, sparsely pubescent with simple 1-3-celled uniseriate trichomes like those of the stems, especially on young leaves. Infl orescences 1.5-3.0 cm long, simple, lateral, leaf-opposing or internodal, with 2-6 fl owers, sparsely pubescent with simple uniseriate 4-6-celled spreading trichomes; peduncle 1.0-3.0 cm long, 0.4-0.5 mm in diameter at the apex and 0.6 mm in diameter at the base; pedicels 0.6-0.9 cm long, ca. 0.4 mm in diameter at the base and ca. 0.5 mm in diameter at the apex, straight and spreading at anthesis, articulated at the base; pedicel scars spaced 0.2-1.5 mm apart. Buds globose, white or purple-tinged. Flowers 5-merous, all perfect, nodding; calyx tube ca. 1.4-1.5 mm long, the lobes 1.6-2.0 mm long, rectangular-deltate in outline with rounded to acute apices, somewhat spreading at anthesis, sparsely pubescent with simple 1-4-celled uniseriate trichomes; corolla 1.4-1.6 cm in diameter, white to pale or deep violet-blue, with a dark purple ring and yellow-green central star at the base, stellate, lobed to the middle, the lobes ca. 4.0-5.0 mm long, 2.0-2.5 mm wide, refl exed at anthesis, densely pubescent abaxially with 1-2-celled simple uniseriate trichomes, these usually shorter than the trichomes of stems and leaves, glabrous adaxially; fi lament tube 1.3-1.5 mm long; free portion of the fi laments ca. 1.1-1.6 mm long, pubescent with 4-7-celled uniseriate trichomes at the base adaxially; anthers 3.5-4.0 mm long, 0.8-1.0 mm wide, ellipsoid to rectangular in outline, yellow, poricidal at the tips, the pores lengthening to slits with age; ovary globose, glabrous; style 5-6 mm long, exerted 1.0-1.7 mm beyond the anther cone, densely pubescent with 2-3-celled simple uniseriate trichomes in the basal 2/3; stigma clavate, minutely papillate. Fruit a globose berry, 4-5 mm in diameter, green when developing, the colour when mature unknown, with a few stone cell aggregates in each berry; fruiting pedicels 1.1-3.2 cm long, ca. 0.4 mm in diameter at the base, ca. 0.6 mm in diameter at the apex, spreading, becoming somewhat woody; fruiting calyx lobes 2.8-3.2 mm long, spreading. Seeds 15-20 per berry, ca. 1.5-1.7 mm long, ca. 1.2-1.3 mm wide, fl attened, reniform, pale-brown, the sub-lateral hilum positioned close to the middle, the testal cells pentagonal in outline. Ecology. Flowering and fruiting during the wet season, generally from October-March, with a single record known from August.
Etymology. Th e epithet refers to the leaf shape, which struck the collector of the type (MN) as like that of Alliaria petiolata (M.Bieb.) Cavara & Grande (Brassicaceae), a European species invasively adventive in the eastern USA and other temperate areas of the world.
Conservation status. We assign a preliminary IUCN threat status of Vulnerable (VU, B1) to S. alliariifolium based on the small extent of occurrence (EOO=16,136 km 2 ). Th e area of occupancy is even smaller (AOO=40 km 2 ) and would merit status as endangered (EN), but knowing that collection densities in the tropical Andes remain extremely low and that the collections are mainly along the sparse road network, we prefer basing our assessment on the extent rather than area of occurrence. No occurrences are known within the protected area network in Bolivia thus far, but collection data indicates that the species endures grazing pressures relatively well.  Discussion. Solanum alliariifolium is distinct within the Morelloids in being a slender creeping herb rooting at the nodes, with broadly ovate to orbicular leaves with undulate to shallowly lobed margins. It is morphologically most similar to S. leptocaulon Van Heurck & Müll.Arg., which occurs in similar montane habitats in Bolivia and in southern Peru, but the latter species is a small scrambling shrublet with ovate-lanceolate leaves with entire margins. Solanum leptocaulon further diff ers from S. alliariifolium in having a campanulate corolla lobed only 1/3 of the way to the base, rather than a stellate corolla lobed to 2/3 to the base with the lobes clearly refl exed at anthesis. Diagnosis. Like Solanum pygmaeum Cav., but diff ering in having mostly 1-branched infl orescences with 6-15 fl owers, anthers < 3.5 mm long, strongly recurving fruiting pedicels, and berries < 1 cm in diameter with fewer than 30 seeds.  Description. Rhizomatous herb with erect stems up to 15-50 cm tall arising from an underground rhizome. Stems 1.5-4.0 mm in diameter at base, slightly fl exuose, terete to ridged, often slightly winged, often purple-coloured, glabrous to sparsely pubescent with appressed 1-4-celled simple uniseriate trichomes ca. 0.5 mm long. Sympodial units difoliate, not geminate. Leaves simple, 2.3-8.0 cm long, 1.2-4.3 cm wide, ovate-lanceolate; adaxial surface glabrous or sparsely pubescent with 1-2-celled spreading hairs along lamina and veins; abaxial surface pubescent only along veins; primary veins 4-6 pairs; base attenuate to decurrent; margins lobed to entire, often purple-tinged, pubescent with short, 1-celled simple uniseriate trichomes, if present lobes present throughout or most commonly only in the basal 1/3 of the blade; apex acute to acuminate; petiole 0.5-1.2 cm long, sparsely pubescent with spreading, simple uniseriate trichomes like those of the stems and leaves. Infl orescences 1.5-3.1 cm long, lateral and internodal, simple to 1-branched, with 6-15 fl owers, sparsely pubescent with simple 1-4-celled uniseriate appressed trichomes; peduncle 1.0-2.4 cm long, and if branched, each branch with a rachis 3-4 mm long; pedicels 4-6 mm long, ca. 0.3 mm in diameter at the base and ca. 0.4 mm in diameter at the apex, straight and spreading at anthesis, articulated at the base; pedicel scars spaced 1-2 mm apart. Buds ovoid, white or purple-tinged. Flowers 5-merous, all perfect; calyx tube ca. 2.0-2.5 mm long, the lobes 1.0-1.5 mm long, triangular with acute apices, sparsely pubescent with simple 1-3-celled appressed uniseriate trichomes; corolla 1.2-1.5 cm in diameter, white or fl ushed with blue, with a yellow-green basal star, stellate, lobed 1/2 to 2/3 of the way to the base, the lobes 4.0-5.0 mm long, 2.5-3.0 mm wide, refl exed at anthesis, later spreading, densely pubescent abaxially with 1-2-celled simple uniseriate trichomes, these usually shorter than the trichomes of stems and leaves, glabrous adaxially; fi lament tube 1.2-1.5 mm long; free portion of the fi laments 1.0-1.2 mm long, pubescent along internal side with spreading hairs like those of the stems and leaves; anthers 3.2-3.5 mm long, 0.9-1.0 mm wide, ellipsoid or rectangular in outline, yellow; ovary globose, glabrous; style 6-7 mm long, exerted 2.5-3.0 mm beyond the anther cone, densely pubescent with 4-celled simple uniseriate trichomes in the basal 2/3; stigma globose, minutely papillate. Fruit a globose berry, 6-7 mm in diameter, pale green (mature ?), with a few stone cell aggregates; fruiting pedicels 1.2-1.4 mm long, ca. 0.6 mm in diameter at the base, ca. 0.8 mm in diameter at the apex, strongly recurving; fruiting calyx lobes 2.5-3.5 mm long, appressed to the berry with the tips slightly refl exed. Seeds 15-25 per berry, 1.7-1.8 mm long, 1.4-1.5 mm wide, concave-reniform, pale brown, the hilum positioned towards the narrower end of the seed, the testal cells pentagonal in outline.

Solanum rhizomatum
Distribution. Endemic to the arid interior valleys of the Bolivian Andes in the Departments of Cochabamba, Potosí, Santa Cruz, and probably Chuquisaca, growing in seasonally dry tropical forests and dry matorral vegetation, along slopes and on rocky and sandy soils, often found growing in moist depressions under the shade of Reissek, legumes, grasses, columnar cacti, and Asteraceae herbs; between 1,300 and 2,900 m elevation.
Ecology. Flowering and fruiting during the wet season from Jan. to March. Etymology. Solanum rhizomatum is named for its rhizomatous underground stem. Conservation status. We assign a preliminary IUCN threat status of Least Concern (LC) to S. rhizomatum based on the known extent of the species occurrence (EOO=43,101 km 2 ). Th e extremely small observed area of occupancy (AOO=48 km 2 ) could merit endangered status (EN), but knowing that collection densities in the tropical Andes remain extremely low and considering that current collections are from >10 diff erent localities, we prefer basing our threat status assessment on the extent rather than area of occurrence. It is not known whether S. rhizomatum is similar in its biology and vegetative spread to S. pygmaeum, and further studies may clarify this aspect of potential conservation assessments in the future. No populations are known thus far from the protected area network in Bolivia. Th e growth form that allows eff ective vegetative spreading would indicate that the species can withstand grazing pressures moderately well. Discussion. Solanum rhizomatum is most closely related to S. pygmaeum from central and coastal Argentina (see Barboza et al. 2013), another rhizomatous species of Solanum section Solanum. Solanum rhizomatum diff ers from S. pygmaeum in having mostly 1-branched infl orescences with 6-15 fl owers, anthers 3.2-3.5 mm long, strongly recurving fruiting pedicels, and berries with 15-25 seeds, while S. pygmaeum always has simple (unbranched) infl orescences with 2-6 fl owers, anthers usually >3.5 mm long, fruiting pedicels that are broadly spreading, and berries with >50 seeds. Although these sets of characters overlap to some extent, S. pygmaeum individuals are generally smaller than those of S. rhizomatum (10-20 cm tall), with smaller leaves 1-5 cm long and 0.5-2.2 cm wide, while S. rhizomatum grows 15-50 cm tall, with larger leaves 2.3-8.0 cm long and 1.2-4.3 cm wide. Solanum pygmaeum forms dense colonies in secondary habitats such as railroad sidings, and has been introduced and naturalised in Europe and North America, presumably in boats carrying wool from eastern coastal Argentina (Barboza et al. 2013).
As in many species of Solanum, variation in corolla colour occurs in S. rhizomatum, where corollas vary from white to pale lilac even within single individuals. Label information from Nee & Mendoza 57594 notes changes in the corolla colour during development, where the corolla is white in bud, violet in anthesis, and darker after wilting.