Solanum caatingae S.Knapp & Saerkinen , PhytoKeys 108: 3. 2018.

Knapp, Sandra, Saerkinen, Tiina & Barboza, Gloria E., 2023, A revision of the South American species of the Morelloid clade (Solanum L., Solanaceae), PhytoKeys 231, pp. 1-342 : 1

9. Solanum caatingae S.Knapp & Saerkinen, PhytoKeys 108: 3. 2018.

Fig. 30

Type.

Brazil. Bahia: Mun. Maracajú, Lagoa Itaparica 10 km W of São Inacio-Xique-Xique road at the turning 13.1 km N of São Inacio, 300-400 m, 26 Feb 1977, R.M. Harley [with S.J. Mayo, R.M. Storr & T.S. Santos] 19125 (holotype: RB [RB00464327, acc. # 271981]; isotypes: CEPEC [acc. # 19367], K [K001336337]) .

Description.

Perennial herbs, 0.4-1 m high, perhaps occasionally annual or only persisting for a few years. Stems terete or slightly angled, lacking spinose processes; young stems densely to sparsely pubescent with spreading glandular, simple uniseriate trichomes 0.5-1 mm long, the trichomes 4-15 celled, drying translucent; new growth densely glandular pubescent; bark of older stems greenish-brown or pale tan. Sympodial units unifoliate or difoliate, the leaves not geminate. Leaves simple, shallowly toothed, the blades 2.5-10 cm long, 1-4.5 cm wide, ovate to broadly elliptic, widest in the lower half, membranous, concolorous; adaxial and abaxial surfaces evenly glandular-pubescent with simple uniseriate trichomes to 2 mm long, these denser abaxially and along the veins, densely pubescent with minute glandular papillae on both leaf surfaces especially in young leaves; principal veins 4-6 pairs, drying paler than the lamina; base truncate and then abruptly attenuate on to the distal part of the petiole; margins shallowly and irregularly toothed, the teeth ca. 0.5 mm long, rounded at the tips and broadly deltate to semi-circular in outline; apex acuminate, the tip blunt; petiole (0.5) 1-2 cm, only winged from the attenuate leaf base in the distal half to third. Inflorescences internodal, unbranched or forked, subumbelliform with most flowers in the distal portion or spaced ca. 0.5 mm apart, 2-3.5 cm long, with 5-8 flowers, densely and finely glandular-pubescent like the stems and leaves; peduncle 1.8-3 cm long; pedicels 0.7-0.8 cm long at anthesis, ca. 0.5 mm in diameter at the base, ca. 0.7 mm in diameter at the apex, slender and tapering, densely glandular-pubescent with short uniseriate trichomes and glandular papillae, spreading at anthesis, articulated at the base but the articulation point somewhat swollen and leaving a minute stump that is darker in colour than the axis, this especially visible in fruiting material; pedicels scars closely packed in the distal part of the inflorescence to 0.5 mm apart, with the lowermost ca. 1 mm distant from the rest. Buds globose to broadly ellipsoid, the corolla strongly exserted from the calyx tube before anthesis. Flowers 5-merous, cosexual (hermaphroditic). Calyx tube 1-1.5 mm long, conical to broadly conical, the lobes 1-1.5 mm long, ca. 1 mm wide, deltate and spathulate, densely glandular-pubescent like the pedicels with uniseriate trichomes and papillae, the tips rounded. Corolla 0.6-0.9 cm in diameter, white with a darker (green?) central star, stellate, lobed 2/3-3/4 of the way to the base, the lobes 2.5-3.5 mm long, 1.5-3 mm wide, triangular, reflexed to spreading at anthesis, the abaxial surfaces glabrous to sparsely papillate with a few glandular trichomes ca. 0.2 mm long. Stamens equal; filament tube minute; free portion of the filaments 0.5-1 mm long, glabrous or sparsely pubescent with a few weak tangled simple uniseriate trichomes adaxially at the very base; anthers 1.8-2.2 mm long, 0.7-1 mm wide, ellipsoid, bright yellow, smooth, poricidal at the tips, the pores elongating to slits with age. Ovary conical, glabrous; style 3.5-4 mm long, straight, exserted beyond the anther cone, sparsely glandular pubescent with weak tangled trichomes and papillae in the basal half where included in the anther cone; stigma minutely capitate, densely papillate, not markedly different from the style. Fruit a globose berry, 0.7-1 cm in diameter, green when young, maturing shiny black, the pericarp thin, not translucent when dry (drying black), opaque, glabrous; fruiting pedicels 0.9-1.2 mm long, tapering from a base ca. 1 mm in diameter to an apex 1-1.2 mm in diameter, not distinctly woody, spreading and becoming deflexed at fruit maturity, persistent and remaining on inflorescence; fruiting calyx not accrescent, the tube 1-1.5 mm long, the lobes 2-2.5 mm long, spreading and later reflexed, covering the lower ca. 1/4 of the berry, the abaxial surfaces not densely papillate (different from S. americanum where the surfaces are densely papillate). Seeds (30)50-80 per berry, 1-1.5 mm long, 1-1.2 mm wide, teardrop shaped with a subapical hilum, reddish-gold, the surfaces minutely pitted, the testal cells pentagonal. Stone cells absent. Chromosome number: Not known.

Distribution

(Fig. 31 ). Solanum caatingae is endemic to Brazil; widely scattered collections are known from the States of Bahia, Ceará, Paraiba, Piauí and Goiás.

Ecology and habitat.

Solanum caatingae grows in dry formations known as “caatinga” or "savana estépica” ( Eiten 1983; Prado 2003; IBGE 2004), between 300 and 400 m elevation. The caatinga is a complex mosaic of many biomes, ranging from the thorn forests of the caatinga proper (see Andrade-Lima 1981) to gallery forest, to humid forests on higher elevations ("brejos de altitude") and cerrado savannas ( Andrade-Lima 1981; Lleras 1997). Like many other morelloid species, S. caatingae apparently grows in somewhat disturbed and moist areas within the broader more xerophytic habitat and details of its ecological preferences will remain somewhat unclear until more field observations and collections can be made.

Common names and uses.

None recorded.

Preliminary conservation status

( IUCN 2022). Endangered (EN - B2 a, b(ii, iii, iv)). EOO = 267,575 km2 [LC]; AOO = 32 km2 [EN]. In spite of its large EOO, we suggest that S. caatingae merits the status of Endangered, as did Knapp and Särkinen (2018). The caatinga habitat is highly fragmented and under severe threat from fire and agriculture. Further studies in this dry forest habitat will certainly reveal more populations of this interesting species.

Discussion.

Solanum caatingae is morphologically most similar to the widespread circumtropical weed S. americanum . It differs from S. americanum most strikingly in its spreading glandular pubescence of translucent trichomes (versus appressed eglandular pubescence of white trichomes), its usually more deeply and sharply toothed leaf margins and longer anthers (ca. 2 mm long versus ca. 1.5 mm long). Several other glandular pubescent species of herbaceous solanums occur in the dry forests of South America, but these are mostly from the Chaco biome and do not overlap in distribution with S. caatingae (see Särkinen and Knapp 2016). Solanum caatingae can, however, be distinguished from these species (e.g., S. michaelis , S. nitidibaccatum , S. physalidicalyx , S. physaliifolium , S. tweedieanum and S. woodii ) by its calyx that is not accrescent in fruit with the lobes spreading or slightly reflexed and its shiny black berries with no stone cells. The glandular-pubescent Amazonian species S. arenicola differs from S. caatingae in its larger flowers (8-12 mm in diameter versus 6-9 mm in diameter), longer anthers (3-4 × 0.8-0.9 mm versus 1.8-2.2 × 0.7-1 mm) and smaller berries (3.5-7 mm versus 7-10 mm in diameter) that contain stone cells. Solanum caatingae can be distinguished from S. tweedieanum in its smaller anthers (1.8-2.2 mm versus ca. 5 mm long), non-accrescent calyx in fruit ( S. tweedieanum has an accrescent calyx) and distribution (northeastern Brazil versus Argentina, Bolivia, and Paraguay).

Sendtner (1846) included a specimen of S. caatingae (collected by E. Pohl from Rio Maranhão, probably Pohl 2393 from W) in his concept of S. nigrum subsp. atriplicifolium (Gillies ex Nees) Sendtn. (= S. tweedieanum ). Solanum caatingae can be distinguished from S. tweedieanum in its smaller anthers (1.8-2.2 mm versus c. 5 mm long), non-accrescent calyx in fruit ( S. tweedieanum has an accrescent calyx) and distribution in low elevation Brazil versus the eastern slopes of the Andes in the Southern Cone.

Figures

Figure 30. Solanum caatingae A habit B inflorescence in bud C inflorescence with flowers D mature, shiny black fruits with reflexed calyx lobes (A, C, D Harley et al. 19125 [RB 00464327, acc. # 27181] B Costa-Lima et al. 1862 [RB 01145300, acc. # 654975]). Reproduced with permission of Jardin Botanico de Rio de Janeiro.

Figure 31. Distribution map of Solanum caatingae.