Solanum friburgense Giacomin & Stehmann, 2014

Giacomin, Leandro L. & Stehmann, Joao R., 2014, Three new species of Solanum (Brevantherum Clade) endemic to the Brazilian Atlantic Forest, PhytoKeys 38, pp. 69-87 : 76-79

Solanum friburgense Giacomin & Stehmann sp. nov. Figs 2C , 4

Diagnosis.

Differs from Solanum inornatum Witasek in its elliptic leaves with attenuate bases and cuspidate apices, its leaf pubescence of upright spreading trichomes denser along the veins, its 2-foliate sympodial units, and its strongly recurved calyx lobes at anthesis. Also differs from Solanum bradei Giacomin & Stehmann by its conspicuous, linear-lanceolate calyx lobes.

Type.

BRAZIL. Rio de Janeiro: Mun. Nova Friburgo. Reserva Ecológica de Macaé de Cima, trilha para o Vale dos xaxins. 27 Oct 1990 (fl), A. Amorim, B.C. Kurtz & L. Sylvestre 276 (holotype: RB [RB-00413518]; isotype: BHCB).

Description.

Herbs to shrubs, woody at base, few-branched, rhizomatous, up to 50 cm high, the branches on new growth ascending, becoming prostrate. Stems densely hispid-pubescent with uniseriate simple upright, spreading trichomes ca. 2.6 mm long, with up to 3 cells. Bark of older stems becoming light brown, glabrescent; new growth greenish brown, shiny. Sympodial units 2-foliate, not geminate. Leaves simple, solitary, the blades 3-11 × 1-5 cm, elliptic, chartaceous, slightly discolorous, drying darker above, not shiny, sparsely pubescent on both surfaces with simple trichomes like those of the stems, the trichomes denser along the veins (of any order); base attenuate, slightly decurrent onto the petiole; margins entire, ciliate, with spreading trichomes like those of the blade; apex acute to acuminate; petioles 6-12 mm long, with as pubescence like that of the stems; venation brochidodromous; midrib and secondary veins visible to the naked eye, prominent on both surfaces. Inflorescences sessile, lateral, unbranched cymes of 1-4 flowers; pedicels 4-12 mm long in flower, unknown in fruit, nearly contiguous. Calyx 3-5 mm long, deeply lobed, the tube ca. 1 mm long, the lobes 3-4 mm long, ca. 1mm wide, linear-lanceolate, densely pubescent abaxially with trichomes like those of the stem, glabrous adaxially, strongly recurved at anthesis. Corolla 1.4-1.8 cm in diameter, white, stellate, membranaceous, the lobes 5-7 × 2-3 mm, ovate-lanceolate, sparsely pubescent abaxially mainly along the midrib with trichomes like those of the calyx but shorter, up to 1.5 mm long, glabrous adaxially. Stamens 3-5 mm long, equal in length, the filaments ca. 1 mm long; anthers 2-4 mm long, ca. 1 mm wide, oblong, slightly connivent, yellow, the base cordate, the apex emarginate and poricidal, the subapical pores directed introrsely, not opening into longitudinal slits. Ovary glabrous; style white, 4-5 mm long, straight, cylindrical, the stigma light green, capitate. Fruit unknown.

Distribution.

Narrowly endemic, known from only two localities in the municipality of Nova Friburgo in the state of Rio de Janeiro, Brazil ( Fig. 3 ). Both localities are within conservation units, one public (Reserva Ecológica de Macaé de Cima) and one private (RPPN Bacchus).

Ecology.

Rare in the understory of well-preserved fragments of the Brazilian Atlantic coastal rainforest, at elevations of about 1,500 m. The species always shows a well-developed rhizome system. This suggests the plant invests heavily in vegetative propagation, which is consistent with the few flowering specimens found in the field. In cultivation, so few flowers were produced that no crossing studies were performed.

Phenology.

The flowering material studied was collected in October and November but one of these is from cultivation. The fruits are unknown.

Etymology.

The species is named after the municipality where all known collections are from, Nova Friburgo, in the state of Rio de Janeiro.

Preliminary conservation status

(IUCN, 2013). Critically Endangered (CR) B1; B2 ab (iii, iv). Solanum friburgense is known from two localities closely situated to each other within the same municipality, that represents an AOO of 8 km2. The type specimen was collected in 1990 and despite an intensive inventory that was recently carried out in the area ( Lima and Guedes-Bruni 1997), no additional collections were made until 2009. Although the EOO could not be calculated because only two points are available, if the species is actually endemic to Nova Friburgo and surroundings it would probably fit the Critically Endangered category (less than 100 km2). Even considering the occurrence within two conservation units and the paucity of material available for analysis, we provisionally suggest it to be assessed as Critically Endangered, regarding it seems to have a reproductive system based on vegetative propagation (see Discussion below). Within RPPN Bacchus two large populations are known (about 50 individuals), but no flowering specimens were observed in the field over three consecutive years (2009, 2010 and 2011).

Discussion.

Solanum friburgense is the only species of the Solanum inornatum group that has 2-foliate non-geminate sympodial units. It shares the linear-lanceolate calyx lobes with Solanum inornatum but can be distinguished from it by having the calyx lobes strongly recurved at anthesis, and the leaf pubescence concentrated along the veins and only sparsely present on the mesophyll of the leaf lamina, while Solanum inornatum has straight to slightly curved calyx lobes and trichomes evenly distributed on veins and mesophyll. The leaf shape is also a good character to separate the species: Solanum friburgense has elliptic leaves with attenuate bases and cuspidate apices and Solanum inornatum ovate leaves with rounded bases and attenuate apices. Solanum friburgense can be readily distinguished from Solanum bradei in its conspicuous linear-lanceolate calyx lobes versus tiny deltate calyx lobes of the former.

As for all species of the Solanum inornatum group, Solanum friburgense has very discrete and almost hidden inflorescences, that are covered by the leaves if seen from above. This cryptic flowering could be the reason why the oldest known collection of the species is very recent, from the 1990s.

The species has an intriguing reproductive system, apparently based mainly on vegetative propagation. Although two large populations were found at RPPN Bacchus, no flowering specimens were seen in three consecutive years of field work encompassing almost three months of the rainy season, when the two only flowering specimens were collected. No fruit was seen in the field or produced in cultivation, and we believe that the few known specimens are the result of a very restricted distribution and not a lack of collecting effort. Solanum friburgense inhabits the understory of primary cloud forest fragments, which are not uncommon in the mountain ranges surrounding Nova Friburgo, suggesting that its restricted distribution is due to its vegetative reproductive strategy and not habitat specificity. Future efforts should be made to locate this species at nearby reserves in Rio de Janeiro state such as Parque Estadual dos Três Picos, in Nova Friburgo and Parque Nacional da Serra dos Orgãos, in Teresópolis, in order to search for additional populations.

Specimens examined.

BRASIL. Rio de Janeiro: Mun. Nova Friburgo. Macaé de Cima, Sítio do Srs. David e Isabel Muller, Trilha que leva para topo da serra, passando pela antena; espécime floresceu em casa de vegetação na Fundação Zoo-Botânica de Belo Horizonte, 1577 m, 22°22'24.64", 42°30'17.5", 20 Oct 2009 (fl), L.L. Giacomin 940 (BHCB); RPPN Bacchus, Macaé da Cima, owned by David and Isabel Miller, Trilha do Telefone, 1555 m, 22°22'27"S, 42°30'04"W, 29 Apr 2010 (veg), M.F. Agra et al. 7293 (BHCB, JPB).

Figures

Figure 2. Photographs of the species in the field. A-B Solanum bradei Giacomin & Stehmann A Shoot showing the anisophyllous sympodia and lateral emergence of the inflorescence [from Hattori et al. 914 (BHCB)] B Translucent fruit [from Agra et al. 7398 (BHCB, JPB)] C Inflorescence of Solanum friburgense Giacomin & Stehmann in cultivation showing its hispid indumentum [from Giacomin 940 (BHCB)] D Inflorescence of Solanum kriegeri Giacomin & Stehmann [from Giacomin et al. 770 (BHCB); photo by F. D. Gontijo]. Scale bars A = 2 cm; B-D = 1 cm.

Figure 3. Known distribution of Solanum bradei Giacomin & Stehmann (circles), Solanum friburgense Giacomin & Stehmann (stars) and Solanum kriegeri Giacomin & Stehmann (triangles) in the states of Minas Gerais (MG), Rio de Janeiro (RJ) and Sao Paulo (SP) in southeastern Brazil.

Figure 4. Solanum friburgense Giacomin & Stehmann. A Rhizomatous habit B Detail of the typical leaf shape and indumentum C Inflorescence detail, showing the diagnostic recurved calyx at anthesis. All from Giacomin 940 (BHCB). Scale bars A = 10 cm; B = 1 cm; C = 5 mm. Drawings by M. M. Duarte and B. Raddichi.