Research Article |
Corresponding author: Sandra Knapp ( s.knapp@nhm.ac.uk ) Academic editor: Leandro Giacomin
© 2018 Sandra Knapp, Tiina Särkinen.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Knapp S, Särkinen T (2018) A new black nightshade (Morelloid clade, Solanum, Solanaceae) from the caatinga biome of north-eastern Brazil with a key to Brazilian morelloids. PhytoKeys 108: 1-12. https://doi.org/10.3897/phytokeys.108.27254
|
Solanum caatingae sp. nov. is described from the arid caatinga biome of north-eastern Brazil. It is known from only a few specimens, but these were found amongst the many sheets of the widespread circumtropical weed S. americanum Mill.; it is possible that more will be found once its distinct nature has been recognised. It differs from S. americanum and all other herbaceous black nightshades known in Brazil, in its combination of glandular pubescence and shiny black fruit with small spreading sepals. The description of S. caatingae brings the number of morelloid solanums in Brazil to seven and a key is provided for their identification.
Brazil, dry forests, endemism, identification key, new species, Solanum , Solanaceae , weeds
Solanum L. is one of the most species-rich vascular plant genera in South America (
Within Solanum, the Morelloid clade is a group of ca. 75 species most of which are endemic to the tropical Andes (
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 (
The description of S. caatingae is based on examination of herbarium specimens from CEPEC, HUEFS, RB and W (acronyms follow Index Herbariorum; http://sweetgum.nybg.org/science/ih/). Specimens of this species may be found identified as S. americanum in other herbaria, but in our extensive work on the morelloid solanums in European, American and Latin American herbaria (see
Specimens with coordinates were mapped directly and those lacking coordinates were located using Google Earth and gazetteers. The 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. The preliminary conservation status was assessed using the
Like Solanum americanum Mill., but differing in its glandular pubescence on all vegetative parts, larger flowers with longer anthers, glabrous adaxial calyx lobe surfaces and spreading to appressed calyx lobes in fruit.
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 alt., 26 Feb 1977, R.M. Harley [with S.J. Mayo, R.M. Storr & T.S. Santos] 19125 (holotype: RB [RB00464327, acc. # 271981]; isotype: CEPEC [acc. # 19367]).
Perennial herb, 0.4–1 m tall, perhaps occasionally annual or only persisting for a few years. Stems terete or slightly angled, lacking spinescent 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, 2.5–10 cm long, 1–4.5 cm wide, ovate to broadly elliptic, widest in the lower half, membranous; 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, 2–3.5 cm long, subumbelliform with most flowers in the distal portion or spaced ca. 0.5 mm apart, unbranched or furcate, 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 a minute stump that is darker in colour left on the rhachis, 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, all perfect. 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, 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 but not translucent when dry (drying black); 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, 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 to S. americanum where the surfaces are densely papillate). Seeds (30)50–80 per berry, 1–1.5 mm long, 1–1.2 mm wide, tear-drop shaped with a subapical hilum, reddish-gold, the surfaces minutely pitted, the testal cells pentagonal. Stone cells absent. Chromosome number: Not known.
Solanum caatingae grows in dry formations known as “caatinga” or “savana estépica” (
The species epithet is a genitive noun and comes from the caatinga vegetation formation (e.g.
(
Solanum caatingae is morphologically most similar to the widespread circumtropical weed S. americanum. It differs from it most strikingly in its spreading glandular pubescence of translucent trichomes (versus appressed eglandular pubescence of white trichomes) 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
Several species of European and African polyploid morelloids (e.g. S. nigrum L., S. retroflexum Dunal, S. villosum Mill.) are polymorphic for presence or absence of glandular trichomes and their occurrence does not correlate with relationships based on phenetic studies with molecular markers (
The type collection (Harley et al. 19125) comes from near the edge of the Caatinga Biogeographic Domain as defined by the Instituto Brasileiro de Geografia e Estatística (
(paratypes). BRAZIL. Ceará: Mun. Lavras de Mangabeira, area a ca. 12 km a N do Distrito de Felixardo, 299 m, 24 Jul 2014, A. Costa-Lima et al. 1406 (HUEFS, RB). Goiás: Rio Maranhão, sin.dat., J.B.E. Pohl 2393 (W). Paraiba: Mun. Carrapateira, Sitio Volta, nos arredores do Açude Volta, 404 m, 24 Sep 2014, A. Costa-Lima et al. 1862 (HUEFS, RB).
Solanum arenicola is included here although it has not yet been recorded for Brazil; the species is known from adjacent Peru and Bolivia in lowland Amazonian rainforest.
1 | Plants with simple glandular pubescence on stems and leaves | 2 |
– | Plants with simple eglandular trichomes (without glandular tips) on stems and leaves | 4 |
2 | Calyx markedly accrescent in fruit, covering more than half of the berry; flower buds completely enclosed within the calyx lobes; rare annuals of coastal habitats in southern Brazil (mostly known from Argentina) | Solanum sarrachoides Sendtn. |
– | Calyx not markedly accrescent in fruit, the lobes spreading and only covering ca. 1/4 of the berry; flower buds strongly exerted from the calyx lobes; perennials (annuals?) of dry areas within the Caatinga Domain in north-eastern Brazil or in moist Amazonian lowland rain forest in western Brazil | 3 |
3 | Anthers 1.8–2.2 mm long; calyx lobes deltate-rounded with rounded apices; mature berry shiny black or purplish-black, without stone cells; in dry areas within the Caatinga Domain in north-eastern Brazil | Solanum caatingae S.Knapp & Särkinen |
– | Anthers 3–4 mm long; calyx lobes long-triangular with acuminate apices; mature berry matte purple-black, with stone cells; in moist Amazonian lowland rain forest probably in western Brazil (not yet recorded) | Solanum arenicola Särkinen & P.Gonzáles |
4 | Anthers 0.8–2.5 mm long | 5 |
– | Anthers (2.5-) 3.5–5.5 mm long | 6 |
5 | Anthers 0.8–1.5 mm long; fruiting pedicels spreading, not recurved or reflexed; calyx lobes in fruit ca. 1 mm long, strongly reflexed; fruits drop off without pedicels and calyx, leaving behind peduncles with pedicels and calyces still attached; berries shiny black, with 0–4 stone cells; widespread weed | Solanum americanum Mill. |
– | Anthers 1.5–2.5 mm long; fruiting pedicels recurved; calyx lobes in fruit 1.5–3.0 mm long, appressed to the berry, not reflexed; pedicels drop off with fruit, leaving peduncles behind; berries matte black, with no stone cells; in littoral from Santa Catarina to Ceará, less commonly inland | Solanum chenopodioides Lam. |
6 | Leaf bases truncate; leaves broadly delate to ovate; inflorescence unbranched (rarely furcate); calyx lobes in fruit ca. 1 mm long; lowlands in southern Brazil, from inland or along Amazonian rivers | Solanum pilcomayense Morong |
– | Leaf bases attenuate, often decurrent on the petiole; leaves lanceolate, elliptic or more rarely ovate; inflorescence branched or less commonly unbranched; calyx lobes in fruit >1 mm long; Amazonian or southern Brazil | 7 |
7 | Calyx lobes long triangular with acuminate apices; corolla lobes long and narrow; buds more than 2 times longer than wide, narrowly ellipsoid; plants of lowland Amazonia probably occurring in western Brazil (not yet recorded) | Solanum arenicola Särkinen & P.Gonzáles |
– | Calyx lobes deltate or triangular with acute apices; corolla lobes deltate; buds ca. 2 times longer than wide, ellipsoid; plants of south-eastern Brazil | 8 |
8 | Anthers (2.5-) 3.5–4.5 mm long; pedicels tightly to loosely spaced, recurving/reflexed in most specimens and fruiting inflorescences appearing secund; calyx lobes in fruit 1.5–2 mm long, appressed to the berry; corolla with a dark purple eye, lobed nearly to the base, the lobes strongly reflexed at anthesis; berries with 2 small stone cells; 0–1,700 (-2,300) m elevation in southern Brazil | Solanum paucidens Bitter |
– | Anthers 4.4–5.5 mm long; pedicels arising closely together yet regularly spaced 1 mm apart, spreading in fruit; calyx lobes in fruit 1.5–2.5 mm long, slightly spreading; corolla with a yellow eye, lobed to 1/2–2/3 to the base, the lobes spreading at anthesis; berries without stone cells; above 2,000 m elevation in coastal mountains of Minas Gerais, Rio de Janeiro and São Paulo | Solanum enantiophyllanthum Bitter |
We thank the curators of the herbaria cited in the text and in the Supplementary Material file for permission to use specimens in their care, especially Luciano Queiroz for finding duplicates of S. caatingae at HUEFS; funding for SK’s work in the herbarium in Vienna (W) where this species was first seen was provided by the SYNTHESYS Project http://www.synthesys.info/ financed by European Community Research Infrastructure Actions under the FP6 and FP7 “Structuring the European Research Area” Programme, her visit to Brazil in 2018 was funded by the Rutherford Fund (Department of Business, Energy and Industrial Strategy (BEIS), UK Government).
Specimen data for species of the Morelloid Clade occurring in Brazil