A new species of Solanum sect. Acanthophora (Solanaceae) from Argentina and Brazil

Abstract A new species of Solanum belonging to section Acanthophora (subgenus Leptostemonum) from Argentina and Brazil is described. Solanum neei Chiarini & L.A.Mentz, sp. nov. is found in clearings of semideciduous forests and in secondary formations, from the states of Paraná, Rio Grande do Sul and Santa Catarina in Brazil to the Misiones province in Argentina. It is morphologically similar to Solanum incarceratum Ruiz & Pav. from Peru, Bolivia and Western-Central Brazil, differing mainly by its pedunculate inflorescences. A key to related species is provided, as well a photograph of the holotype, a distribution map and illustration.


Introduction
Th e Solanaceae is a cosmopolitan family of considerable economic importance with its centre of diversifi cation in South America (D'Arcy 1991, Hunziker 2001. It includes 92 genera and around 2300 species, Solanum L. being the largest genus with ca. 1400 species. Within this genus, a remarkable natural group is subgenus Leptostemonum (Dunal) Bitter (the so-called "spiny solanums"), which includes cultivated representatives such as S. melongena L. (eggplant), S. quitoense Lam. (naranjilla or lulo) and S. sessilifl orum Dunal (cocona or cubiu). Other species, including S. elaeagnifolium Cav.
(silverleaf nightshade), S. sisymbriifolium Lam. (sticky nightshade or wild tomato) and S. carolinense L. (horsenettle) are noxious weeds. Subgenus Leptostemonum includes section Acanthophora Dunal, whose members are characterized by the presence of simple hairs on the upper leaf surface , Nee 1991. Th is section is monophyletic ) and comprises about 20 herbs or small shrubs adapted to disturbed areas and secondary open forests with its center of diversity in eastern Brazil. Some of its species are considered invasive weeds [e.g. S. viarum Dunal (''tropical soda apple''), naturalized in USA, Africa, and Asia (Bryson andByrd 1994, Welman 2003), and S. palinacanthum Dunal (''pocote'', ''joá bagudo'') which invades roadsides and crop fi elds in Argentina and Brazil (Mentz andOliveira 2004, Nee 1991)]. Conversely, other species of sect. Acanthophora are cultivated as ornamentals (e.g. S. mammosum L., ''apple of Sodom'', ''cow's udder'' or ''nipple fruit''; and S. capsicoides All., ''cockroach berry''). Section Acanthophora is especially diverse with respect to the fruit, which can be a berry or a carcerulus (a fruit resembling the true berries, but with an aerial space between the seeds and the pericarp at maturity), small or relatively large (1.35-4 cm diam.), orange, red, yellow, or greenish yellow, and the seeds can be winged or not (Levin et al. 2005, Chiarini andBarboza 2009). Th is variability is also seen in microscopic structures, such as sclereids, layers of spongy tissue and crystals at the hypodermis, which are all related to diff erent dispersal syndromes (Chiarini and Barboza 2009). Nee (1979a) provided a taxonomic treatment of sect. Acanthophora in his doctoral thesis, that he subsequently revised slightly (Nee 1979b(Nee , 1991; in all of these he identifi ed several probable undescribed new species known from just a few collections. Since that time, suffi cient material has accumulated to formally describe one of these, and it is named in honor of Dr. Michael Nee to commemorate his work on the section. Diagnosis. Diff ers from Solanum incarceratum Ruiz & Pav. by its infl orescences with unarmed or prickly peduncles 1.8-4 cm long (versus sessile infl orescences in S. incarceratum); also diff ers from S. acerifolium Dunal and S. atropurpureum Schrank by its unequal, linear calyx lobes (versus equal, triangular or deltoid calyx lobes in S. acerifolium and S. atropurpureum); the non-petaloid linear calyx lobes also distinguishes it from S. anoacanthum Sendtn., which has petaloid, elliptic-lanceolate calyx lobes.

Solanum neei
Type  Description. Shrub up to 1.7 m tall. Stems sparsely pubescent with glandular hairs (stalked or sessile) and 2-5 celled simple hairs, armed with straight (sometimes recurved), broad-based prickles to 5-10 mm long, and needlelike prickles,1-2 mm long. Sympodial units di-or trifoliate. Leaves solitary or sometimes geminate, if geminate then one of the leaves about twice the size of the other; petioles 3-9 cm long, pubescent with glandular and simple trichomes and armed with acicular prickles to 1.2 cm; blades membranaceous, deltoid, 10-19 × 9-18 cm, with 2-3 pairs of shallow, broadly triangular teeth or lobes, the base truncate or cuneate to subcordate; upper surface with simple, spreading, 2-4-celled eglandular hairs and very short glandular hairs; lower surface moderately to sparsely pubescent with stellate, sessile or shortstalked trichomes, with (3) 4 (6) lateral rays and a central ray (midpoint) the same size or a little longer, and with glandular hairs and prickles on the midvein, the prickles 1-3 mm long, smaller than those of the petioles. Infl orescence extra-axillary, pedunculate, unbranched, scorpioid, (3) 5-25-fl owered, with prickles to 2 mm long; peduncles up to 1.8-4 cm (2.5-5 cm in fruit) unarmed to prickly, with simple and glandular hairs; pedicels up to 3 cm, enlarged towards the apex, unarmed to prickly, with simple and glandular hairs. Flowers all perfect; calyx lobes unequal, elongate, linear-lanceolate to linear, equal to or somewhat shorter than the corolla lobes, 0.6-1.6 cm long and up to 1 mm wide (1.3-2.6 cm long in fruit), pubescent with glandular and simple hairs, sometimes also with some small prickles; corolla stellate, 2.2-2.5 cm in diameter, white, with simple hairs outside, inner surface glabrous, the lobes planar, lanceolate, 12-14 mm long × 4.5-6 mm wide; anthers attenuate, yellow, 8-9 mm long, opening by apical pores; ovary globose covered by small glandular trichomes; style whitish, 10-11 mm; stigma capitate or clavate, green. Fruits globose-ellipsoid, ca. 1.5 cm long × 1 cm wide, variegated when immature, yellow when ripe, subtended by the calyx lobes that are usually longer than the fruit (sometimes the same length or a little shorter). Seeds orbicular, compressed, winged, ± 3 mm diam. Chromosome number 2n = 24 (Acosta et al. 2005, sub nom. Solanum sp. 2). Distribution (Fig. 4). Southern Brazil in the states of Paraná, Rio Grande do Sul and Santa Catarina, Brazil, and in Prov. Misiones, Argentina; 100-1000 m elevation. Solanum neei inhabits the Atlantic Forest region (Alto Paraná Atlantic forest, Araucaria humid forest and Serra do Mar coastal forest), in areas with 1200-2000 mm of annual precipitation.
Ecology. Th e new species is found in clearings of semideciduous primary forests and in secondary forest. Flowering specimens have been collected from September to April; fruiting specimens from October to April.
Etymology. Th e epithet honors Dr. Michael Nee, a specialist in Solanaceae at the Institute of Systematic Botany, New York Botanical Garden (USA). Nee's contributions to the knowledge of this family (and particularly of genus Solanum) are many and remarkable, and include his Ph.D. thesis on the taxonomy of section Acanthophora.
Preliminary conservation status. Solanum neei is a species of open and somewhat disturbed habitats (as are many 'spiny solanum' species) and seems to be fairly evenly distributed within its area (Fig. 4). Th e species has been regularly collected to date. Although not usually common where it occurs, it is not a species of immediate conser- vation concern. Applying the criteria of the IUCN (http://www.iucn.org/) suggests its conservation status should be 'Least Concern' (LC).
A specimen belonging to Solanum neei was placed by Nee (1991) under the name Solanum species B, and later Mentz and Oliveira (2004) described and illustrated it under 'Solanum sp 1', but neither of these works validly publishes it as a new species.
Key to the species of section Acanthophora with fl attened or winged seeds in Southern Brazil/Northern-Eastern Argentina (for all members of the section in the region see Mentz and Oliveira 2004)