Two new non-spiny Solanum (Solanaceae) from the Gran Chaco Americano and a key for the herbaceous glandular-pubescent solanums from the region

Abstract The Gran Chaco Americano is a major savanna woodland system in South America that harbours great plant and animal diversity. Two new herbaceous species of the Morelloid clade of Solanum (largely corresponding to the traditional Solanum section Solanum) are described here from the Bolivian Chaco. Both species are morphologically similar to a group of related species with glandular pubescence and enlarged, foliaceous calyces that includes Solanum atriplicifolium Gillies ex Nees, Solanum nitidibaccatum Bitter, Solanum physalifolium Rusby, Solanum sarrachoides Sendtn. and Solanum tweedianum Hook. Solanum woodii Särkinen & S.Knapp, sp. nov. is unusual in the Morelloid clade in having tapering anthers on short filaments, and is superficially similar to the unrelated Solanum anomalostemon S.Knapp & M.Nee from dry forests in Peru. Solanum michaelis Särkinen & S.Knapp, sp. nov. is distinct in its enlarged calyx with a short tube and long lobes that apparently reflex at fruit maturity. Both new taxa are illustrated, their conservation status assessed, and their distributions mapped. We also provide a key to the glandular-pubescent herbaceous Solanum species of the Chaco vegetation to aid in identification of these taxa.

Th e Gran Chaco Americano is the most extensive dry forest complex in the Americas and the second largest forested lowland area in South America after the Amazon (Galera andRamella 1997, Olson et al. 2000). Th e ecoregion covers 1,100,000 km 2 in eastern Bolivia (19% of the total area of Gran Chaco) and northern Argentina (46%), all of western Paraguay (34%), and a small portion of Brazil (1%) (Galera and Ramella 1997;Olson et al. 2000). Two sub-regions can be recognized: a) the Dry Chaco where the dominant vegetative structure is xerophytic deciduous forest with multiple layers including a canopy, sub-canopy, shrub and herbaceous layer; and b) the Humid Chaco composed of seasonally fl ooded plains covered by wetlands and palm tree savannas. Some authors distinguish seasonally dry tropical forests from Chaco vegetation per se (Pennington et al. 2006), but here we are using a more inclusive categorization. Th e Chaco represents one of the last great undisturbed areas of habitat in South America outside Amazonia, but recent rates of habitat conversion are alarmingly high (Huang et al. 2009;Hoyos et al. 2013;Yanosky 2013). Th e region is poorly explored, but rich in diversity that has been shown to be in rapid decline (Periago et al. 2014). Plant collections from the Chaco region are poorly represented relative to other habitats in the relevant countries; for example, of the 17,961 Paraguayan plant specimens held in the collections of the Natural History Museum (BM), only 0.6% are from the Chaco ecoregion. New collections made from the region are of interest not only for documenting the diversity of this under-collected and highly threatened area (see Galera and Ramella 1997, http://www.worldwildlife.org/ecoregions/nt0210), but also because novelties are likely to be found.
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. 2015c). Th e clade includes fi ve major groups traditionally recognised at the sectional level (sections Solanum, Campanulisolanum Bitter, Parasolanum A.Child pro parte, Chamasarachidium Bitter, and Episarcophyllum Bitter), which are in the process of re-circumscription based on molecular results (Särkinen et al. 2015c). 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. Section Solanum is distinguished by its herbaceous or sub-shrubby habit, infl orescences usually positioned along the internodes, small fl owers and fruits, and the usual possession of stone cells in the fruits (Bitter 1911), which appear as small, seed-like structures that are usually white and spherical rather than fl attened and brown or yellowish brown like the seeds. Th ese stone cells are derived from accretions of sclerenchyma in the mesocarp (Bitter 1911(Bitter , 1914Danert 1969). Although some studies have been done to clarify the taxonomy of the Old World and North American species of the Morelloid group (Edmonds 1977(Edmonds , 1978Schilling 1981), monographic study is needed to aid species identifi cation and to clarify synonymy, especially in Andean South America where most of the species diversity is found (Edmonds 1972;Barboza et al. 2013) and where the Morelloid clade is amongst the most diverse groups of Solanum.
Recent taxonomic work focusing on delivering a global monographic treatment of the Morelloid clade has resulted in the description of various new species from the tropical Andes (Särkinen et al. 2013a(Särkinen et al. , 2015a(Särkinen et al. , 2015b. A further two new species are here described based on morphological and preliminary molecular data from Bolivian Chaco woodlands. A total of six species of Solanum from the Morelloid clade are now known to occur in the Chaco region, and we provide a key for the identifi cation of similar glandular-pubescent herbaceous non-spiny solanums from the Gran Chaco Americano.

Materials and methods
Descriptions are based on fi eld work and examination of herbarium specimens from K, LPB, MO, and NY (acronyms follow Index Herbariorum; http://sweetgum.nybg. org/science/ih/). Many more duplicates of the specimens cited collected by M. Nee and J.R.I. Wood are expected to be found in Bolivian (USZ for Nee, BOLV and USZ for Wood) and other herbaria deposited under Solanum sp. or Solanum physalidicalyx Bitter.
Specimens with coordinates were mapped directly and those lacking coordinates were located using Google Earth and gazetteers. Extent of Occurrence (EOO) and Area of Occupancy (AOO) were calculated using GeoCat (www.geocat.kew.org) with a 2 km cell width for AOO calculation. Th e preliminary 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).
Distribution (Figure 2). Endemic to Bolivia in the Departments of Tarija and Santa Cruz; although the species is to be expected in adjacent Paraguay. Solanum michaelis grows in dry Chaco vegetation and in lower inter-Andean valleys, along slopes in sandy soils in mostly unshaded dry creek beds on bare soil, often in areas that have been burned, or in more humid Chaco vegetation at the edge of "palmares" (stands of Copernicia alba Morong) between 300-900 m elevation.
Ecology. Flowering in March and between June and September, fruiting from June to September probably toward the end of the rainy season (Jan-Apr) and then sporadically with occasional rains during the dry season.
Etymology. Th e species epithet honours Dr Michael Nee, whose collections from Bolivia have provided the much needed material to complete descriptions of many recently published new species within Solanum, including the two described here. His collections and taxonomic work over the past 50 years have contributed to the understanding of morphological diversity of Solanum. His taxonomic work in the genus has been fundamental in resolving and typifying the 6,967 published names of Solanum.
Conservation status. Th e preliminary IUCN (IUCN 2014) threat status of S. michaelis is Endangered (EN) based on the small known extent of the species occurrence (EOO=2,716 km 2 ) as well as the extremely small observed area of occupancy (AOO=20 km 2 ). Although collection densities in the tropical Andes remain low, the very narrow distribution of the new species suggests conservation concern, because S. michaelis is likely to be highly vulnerable to grazing pressure and changes in rainfall patterns due to its ephemeral ecology. Th e Chaco woodlands in Bolivia and Paraguay are highly threatened by land use change due to agricultural expansion and logging (Huang et al. 2009). Two populations of S. michaelis are known to occur within the protected area network in Bolivia, one in the Parque Nacional de Gran Chaco Kaa-lya along the border with Paraguay, and another in the Parque Nacional de Serranía del Aguaragüe. Discussion. Solanum michaelis diff ers from the co-occurring and morphologically similar S. sarrachoides and the higher elevation yungas species S. physalifolium in having larger anthers (2.5-3.2 mm long), while both S. sarrachoides and S. physalifolium have anthers < 2.2 mm long. Solanum physalifolium has similar shiny green-mottled berries, but occurs at higher elevations (1,400-2,900 m) in yungas or wet forest vegetation and has broadly ovate calyx lobes that partially enclose the fruit at maturity. Solanum tweedianum has similar sized anthers but a longer calyx tube (ca. 1.5-2.0 mm in fl ower and to ca. 5 mm or more in fruit) which fully encloses the berry both during development and at fruit maturity (Barboza et al. 2013). Solanum michaelis has similarly long calyx lobes but a shorter calyx tube in both fl ower (0.8-1.3 mm) and fruit (2.0-2.5 mm) that does not enclose the fruit and appears to sometimes have refl exed calyx lobes at fruit maturity (e.g., Fuentes & Navarro 2607).
Distribution (Figure 4). Endemic to Bolivia in the Departments of Chuquisaca and Santa Cruz, growing in Chaco and Chaco forests of inter-Andean valleys, in dry Chaco woodlands on sandy and clay soils near water sources, rivers and in moist depressions in partial or full shade; between 300-1,800 m elevation.
Ecology. Flowering and fruiting during the wet season from January-April. Etymology. Th e species epithet honours John R.I. Wood who has collected extensively in central and eastern Bolivia and mentored numerous young Bolivian botanists. Material collected by John throughout his career has been the basis for the description of many new species, and here we add yet another to that long list.
Conservation status. Th e preliminary IUCN (IUCN 2014) threat status of S. woodii is Vulnerable (VU, B1) based on the small extent of occurrence (EOO=19,656 km 2 ). Th e area of occupancy is even smaller (AOO=36 km 2 ) and would merit status as endangered (EN), but knowing that collection densities in this part of south-central Bolivia remain 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 protected areas in Bolivia thus far.
Additional  Discussion. Solanum woodii is unusual in having tapering, somewhat cone-shaped anthers with a beak-like tip (see Fig. 1C); this character, however, can be diffi cult to see in older fl ower with dehisced anthers. Amongst other glandular-viscid herbaceous solanums it could be confused with S. tweedianum and S. physalifolium. Solanum woodii is sympatric with S. tweedianum but the latter species has longer calyx lobes in fl ower (3.5-5(-7) mm) and fruit (>5 mm), and slightly larger ellipsoid anthers (3.0-)4.0-4.5 mm long that are rectangular in outline (equally wide along their entire length) rather than broadest at the base; the calyx of S. tweedianum is accrescent and completely covers the berry at maturity, while that of S. woodii is spreading and does not become accrescent.
Th e unusual anther shape in S. woodii resembles that of the enigmatic S. anomalostemon S.Knapp & M.Nee described from the dry inter-Andean valley of the Rio Apurimac in southern Peru (Knapp and Nee 2009). Solanum anomalostemon is morphologically unique within Solanum in having cordate anthers, and was thought to belong to the Morelloid clade (Knapp and Nee 2009). Recent molecular phylogenetic evidence, however, showed it belongs to the Mapiriense clade (Särkinen et al. 2015c), along with a small group of species that have similar tapering anthers (see Bohs 2005). Despite the similarity in anther shape, preliminary molecular data suggest S. woodii is a member of the Morelloid clade rather than closely related to S. anomalostemon and other members of the Mapiriense clade (T. Sarkinen, unpubl. data).
Key to glandular-pubescent herbaceous solanums in Chaco vegetation