Solanum lagoense Stehmann, 2016

Stehmann, Joao Renato & Moreira, Nayara Couto, 2016, Solanum lagoense (Solanaceae, Geminata clade), a new species from Lagoa Santa, Minas Gerais State, Brazil, PhytoKeys 61, pp. 15-25 : 16-20

Solanum lagoense Stehmann sp. nov. Figures 1 , 2

Diagnosis.

Solanum lagoense is similar to Solanum restingae S. Knapp, Solanum amorimii S. Knapp & Giacomin, and Solanum psilophyllum Stehmann & Giacomin but differs from them by its pilose stems and longer fruiting pedicels (> 1.5 cm long).

Type.

BRAZIL. Minas Gerais: Município Lagoa Santa, Gruta da Lapinha, Salão dos Bigodes, 19°33'57"S, 43°57'52"W, 716 m, 16 Jan 2015, N.C. Moreira & R. Gurgel 158 (holotype: BHCB [BHCB021206]; isotype: BM).

Description.

Shrub to 1.5 m, rhizomatous, with clonal reproduction; young stems terete, but slightly angled, glabrous or pilose with simple, uniseriate, and recurved trichomes, each with 8-15 cells; new growth always pilose, with stem obviously angled; bark of older stems brown, slightly winged from the leaf bases. Sympodial units difoliate, geminate, the leaves of a pair differing in size, but not usually in shape. Leaves simple; major leaves 5.6-12.4 cm long, 2.2-4.7 cm wide, elliptic, membranous, glabrous on both surfaces, the abaxial surface olivaceous to moss green, the adaxial surface dark green; major veins 7-9 pairs, drying somewhat darker than the lamina and slightly sunken on the adaxial surface, somewhat prominent and lighter on abaxial surface; base attenuate, sometimes slightly asymmetric; margins entire, slightly revolute; apex acute, the tip somewhat blunt; petiole 0.6-1.0 cm long, glabrous; minor leaves 1.6-2.9 cm long, 0.9-1.7 cm wide, differing from major leaves only in size and in having a shorter petiole. Inflorescences 0.2-2 cm long, extra-axillary, arising below the nodes, unbranched, with 1-3 flowers, glabrous; peduncle ca. 3 mm; pedicels 1.4-1.5 cm long, ca. 0.3 mm in diameter, slender, abruptly swollen at the apex, spreading or pendant at anthesis, glabrous, articulated at the base; pedicel scars spaced 0.5-2 mm apart. Buds globose, the corolla strongly exserted from the calyx tube before anthesis. Flowers 5-merous, all perfect. Calyx with the tube ca. 1.0 mm long, broadly conical, the lobes 1.0-1.2 mm long, ca. 1.3 wide, triangular or obtuse, strongly reflexed at anthesis, glabrous adaxially, minutely papillate abaxially, the papillae denser at the tips. Corolla ca. 1.0 cm in diameter, white, stellate, lobed 2/3 of the way to the base, the lobes 1-nerved, ca. 4-5.2 mm long, ca. 2.4-3.6 mm wide, ovate, spreading at anthesis, glabrous, minutely papillate on the margins and the apex, the tips cucullate. Stamens ca. 3.5 mm long; filament tube ca. 0.7 mm long, the free portion of the filaments ca. 0.3 mm long, glabrous; anthers 2.4-2.5 mm long, ellipsoid to slightly obovate, ca. 0.7 mm wide at the base, ca. 0.9 mm wide at the apex, yellow, poricidal at the tips, the pores large and introrse, lengthening to slits with age. Ovary glabrous; style 5-6 mm long, glabrous; stigma not expanded, blunt, the surface minutely papillate. Fruit a subglobose berry, slightly depressed, 1.2-1.3 cm long, 1.3-1.5 cm in diameter, green, darker toward the pedicel, the pericarp not markedly shiny, thick, the mesocarp not juicy; fruiting pedicels 1.7-2.2 cm long, less than 1 mm in diameter at the base, ca. 2 mm in diameter at the apex, gradually expanded to the apex, pendant and hidden under the foliage; fruiting calyx lobes somewhat hyaline, not markedly expanding in fruit, but clearly recurved. Seeds 15-30 per berry, flattened, ellipsoid to irregularly ellipsoid or sometimes ovate-reniform, 3.2-4.0 mm long, 2.8-3.1 mm wide, dark brown, vernicose, with pale incrassate margins, the seed coat obscurely foveolate.

Distribution.

Known only from the type locality at the Gruta da Lapinha, Lagoa Santa, Minas Gerais, in southeastern Brazil.

Specimens examined

(paratypes). BRAZIL. Minas Gerais: Mun. Lagoa Santa, Gruta da Lapinha, Salão dos Bigodes, 19°33'57"S, 43°57'52"W, 716 m, 23 Jan 2015, J. R. Stehmann & N. C. Moreira 6360 (BHCB). Mun. Lagoa Santa, Gruta da Lapinha, Vale Romano, 10°33'57"S, 43°57'57"W, 912 m, 24 Mar 2015, J. R. Stehmann et al. 6361 (BHCB). Mun. Lagoa Santa, Gruta da Lapinha, near Vale Romano, 19°33'57"S, 43°57'48"W, 912 m, 24 Mar 2015, J. R. Stehmann et al. 6374 (BHCB).

Ecology.

Solanum lagoense grows on well-drained soils in the understory of the seasonal forest (Floresta Estacional Semidecidual) that covers the entrance of caves as well as the canyons and blind valleys associated with the carbonatic rocky massifs of Lagoa Santa. This specific habitat is very stable with respect to temperature and humidity throughout the year, in comparison with Cerrado, the typical vegetation matrix in the region. An extensive subterranean system of rhizomes connects individuals in the populations we have sampled (Figure 1B ), indicating that this species is capable of vegetative reproduction. We observed no bees visiting the flowers. The green fruits, hanging and hidden under the foliage, suggest dispersal by bats that inhabit the caves, but the natural history of this species is in need of detailed study.

Phenology.

Flowering specimens were collected in January, occasionally in March, while fruiting material was seen in January, February, and March.

Etymology.

The name refers to Lagoa Santa, a Brazilian locality where two important Danish researchers, Peter Lund and Eugene Warming, worked in the mid 19th century. Warming started his botanical career here studying the Cerrado flora and its ecological relationships. Nowadays he is recognized as one of the Fathers of Ecology.

Preliminary conservation status

(IUCN 2014). Critically Endangered (CR) B1, 2 a, b(ii, iii, iv). This species is known from a single locality, the Gruta da Lapinha, included in the Parque Estadual do Sumidouro, a protected area that encompasses 52 caves. There is an increasing human pressure in its microhabitat near the base of the limestone walls, where many climbing routes are in constant use. The limestone outcrops have being mined for decades, drastically reducing the habitat of this species. The surrounding landscape is changing very quickly with the growth of the municipality of Lagoa Santa, influenced by the Vector North project that fostered the expansion of the metropolitan region of Belo Horizonte, the capital of the state ( Auler and Piló 2015). All of these threats support an assessment of Critically Endangered. Efforts to locate new populations in the conservation unit, as well as in similar habitats associated with caves outside it are needed.

Notes.

Solanum lagoense is a small shrub with entirely glabrous leaves, short inflorescences, few small flowers, and green fruits that are hidden below the foliage. These characters are common in species belonging to Geminata clade, a group that is highly diverse in the Atlantic forest ( Knapp 2002; Knapp et al. 2015). Solanum lagoense is similar to Solanum restingae , Solanum amorimii and Solanum psilophyllum Stehmann & Giacomin due to its glabrous and geminate, but not dimorphic leaves. The latter three species are distinguished by their glabrous stems, even on the new growth, and short fruiting pedicels (up to 1.5 cm long), whereas Solanum lagoense has clearly pilose young stems and longer fruiting pedicels. Solanum restingae is endemic to Bahia and Espírito Santo states and has a strongly winged stem and basally attenuate leaves. Solanum amorimii grows in southern Bahia, but also in far northeastern Minas Gerais; its stem is not winged, the leaves are somewhat auriculate at the base. Despite its occurrence in the region of the Serra do Cipó and the Iron Quadrangle relatively close to Lagoa Santa, Solanum psilophyllum has longer petioles (>1.5 cm) and leaves (>10 cm) and more flowers per inflorescence (5-8).

Other species belonging to the Geminata clade recorded in the southern part of Espinhaço mountains in Minas Gerais are Solanum verticillatum Knapp & Stehmann, Solanum gnaphalocarpon Vell., Solanum intermedium Sendtn., and Solanum warmingii Hiern, the last three collected by Warming in Lagoa Santa and cited or described by Hiern (1877). It is noteworthy that after Warming’s intensive collecting efforts in Lagoa Santa (1863-1866), including the Lapinha and Sumidouro limestone outcrops, few new species have been described in the last decades. This can be due to Warming’s extensive collecting or to the fact that few researchers have been collected recently in the area. Most collecting efforts in the southern Espinhaço chain have been concentrated in rocky quartzite fields (campos rupestres) found in high altitude areas (above 900 m) that houses one of the richest floras of the Neotropical region, almost half of the species endemic ( Echternacht et al. 2011; Giulietti and Pirani 1997).

At first glance, Solanum lagoense also resembles species belonging to Solanum inornatum clade, but the trichomes, leaf arrangement, and number of seeds are quite distinct. While Solanum inornatum group shows trichomes with few cells (up to 4), geminate leaves differing in form, and translucent fruits with few seeds (up to 10) ( Giacomin 2015), Solanum lagoense has multicellular soft trichomes, with more than eight cells, geminate leaves equal in form and hard, green berries with more than 15 seeds per fruit.

The clonal reproduction in Solanum lagoense is noteworthy. All individuals of the population studied have horizontal rhizomes below the leaf litter, linking all the plants together, similar to other members of the Geminata clade such as Solanum arboreum of northern South America ( Knapp 2002) and Solanum psilophyllum of the southern Espinhaço range in Minas Gerais. In Solanaceae , vegetative reproduction is common in the tuber-bearing potatoes ( Hawkes 1990; Spooner et al. 2014), and has also been reported in weedy species of the Leptostemonum clade growing in open places or forest margins such as Solanum viarum Dunal, Solanum palinacanthum Dunal, Solanum guaraniticum A. St.-Hil., and Solanum paniculatum L., all common species of southeastern Brazil ( Mentz and Oliveira 2004). It appears clonal reproduction is widespread across Solanum , and it has been reported in the Cyphomandra, Morelloid, Dulcamaroid, and Brevantherum clades ( Giacomin and Stehmann 2014; Vallejo-Marín and O’Brien 2007). The extent of this habit and reproductive mode is not well-documented in Neotropical solanums largely because the underground parts are rarely collected or even observed in these woody plants (see Knapp 2002).

Lagoa Santa is considered an example of a well-catalogued site. Warming compiled a thorough collection listing 2,593 plant species ( Warming 1908). Our discovery of this new species in Lagoa Santa strengthens the claim for more floristic and taxonomic inventories in Brazil, not only in poorly collected areas such as Amazonia ( Sousa-Baena et al. 2014), but also in “well-studied” areas. In-depth floristic inventories in places with difficult access or with distinct and poorly documented microclimatic conditions, have often resulted in discoveries of new rare and endemic species, even in what appear to be well-catalogued sites.

Figures

Figure 1. Solanum lagoense. A Habit and Nayara Moreira standing close to plants B Clonal reproduction via rhizomes C Geminate leaves of different sizes D Bud E Flower showing the cucullate and spreading corolla lobes F Fruits showing the markedly recurved calyx lobes. A, C, D Stehmann et al. 6360; B, E Stehmann et al. 6361; F Stehmann et al. 6374.

Figure 2. Holotype specimen of Solanum lagoense (N. C. Moreira & R. Gurgel 158 [BHCB 021206]).