Taxonomy
Solanum L., Sp. Pl. 1: 184 (1753), & Gen. Pl. 5th edn, 85 (1754); from the Latin solamen(solace or comfort), possibly alluding to the reputed narcotic properties of the type species.
Type species: S. nigrum L.
Annual or perennial herbs, shrubs or small trees, sometimes trailing or climbing, many species spreading by means of suckers and thus forming colonies (clonal), pubescent with glandular or simple or stellate non-glandular hairs, rarely glabrous; prickles present or absent. Leaves usually alternate, sometimes paired, simple or pinnate, entire or lobed, petiolate. Inflorescence cyme-like, often scorpioid or becoming raceme-like, sub-umbellate or panicle-like, terminal, lateral, axillary, extra-axillary or leaf-opposed. Flowers usually bisexual, rarely male or female, actinomorphic or slightly zygomorphic. Calyx campanulate, rotate or cup-shaped, usually 5 (rarely 4–10)–lobed, sometimes enlarged in fruit. Corolla stellate and deeply incised to rotate, rarely campanulate, purple or blue, less often white or yellow, usually 5 (rarely 4–10)–lobed, the lobes folded in bud. Stamens 5, usually equal, inserted in throat of corolla; anthers bilocular, basifixed, cohering and cone-like around style or not cohering, dehiscing by terminal pores or slits, rarely by longitudinal slits. Ovary 2 (occasionally 3–4)–locular. Stigma terminal, capitate or bifid. Fruit a succulent, papery or bony berry, rarely sub-capsular, sometimes enclosed by inflated calyx. Seeds orbicular to sub-reniform.
A cosmopolitan genus of c. 1500 species, chiefly in tropical and sub-tropical Central and South America with secondary centres of speciation in Australia and Africa.
In Australia there are c. 185 species, many of which are native and endemic. Occurs in all except saline, alpine and aquatic habitats. Many species are weedy, some are common after fire. The highest numbers of species occur in the tropics, but many of these are not well collected and hence are poorly known; juvenile and mature plants may be morphologically very different. Many species occur in arid or semi-arid areas, where they are often widespread; some represent relict distributions.
Dioecious species are confined mainly to tropical W.A. and N.T. Most species have a chromosome number of n=12, some n=23; a few tetraploids and hexaploids occur.
The genus contains the important food plants S. lycopersicon (tomato), S. tuberosum L. (potato) and S. melongena L. (eggplant, aubergine, brinjal). Several species contain steroidal alkaloids and are poisonous or suspected of being toxic. A few, including two Australian species, S. aviculare G. Forster and S. laciniatum Aiton, are cultivated overseas for solasodine as a source of corticosteroid drugs. Several species are cultivated for decorative flowers and foliage (S. seaforthianaum) while a number are classified as noxious weeds in Australia (S. linnaeanum, Apple of Sodom and S. rostratum).
Mature plants of many species show great variation, especially in leaf morphology, distribution of prickles and to a less extent indumentum. Juvenile leaves often differ from adult leaves. In the Lucid key, leaf characters are derived mostly from the adult stage. Ripe fruit are needed for the determination of some species.
R. Brown, Solanum, Prodr. 444–447 (1810); F. Dunal, Solanum, in A.P.de Candolle, Prodr. 13(1): 27–387 (1852); G. Bentham, Solanum, Fl. Austral. 4: 442–465 (1868); K. Domin, CLV. Solanum, Biblioth. Bot. 89: 572–589 (1928–29); G.T.S.Baylis, A cytogenetical study of the Solanum aviculare species complex, Austral. J. Bot. 11: 168–177 (1963); R.J.F. Henderson, Solanum nigrum L. (Solanaceae) and related species in Australia, Contr. Queensland Herb. 16: 1–78 (1974); D.E. Symon, The genus Solanum in Australia, in J.G. Hawkes, R.N. Lester & A.D. Skelding (eds), The biology and taxonomy of the Solanaceae, Linn. Soc. Symp. Ser. 7: 125–130 (1979); N. Peterson, Aboriginal uses of Australian Solanaceae, in J.G.Hawkes et al., op. cit. 171–190; D.E. Symon, A revision of the genus Solanum in Australia, J. Adelaide Bot. Gard. 4: 1–367 (1981).
Changes since the 1982 Flora of Australia treatment
There have been many changes since the Flora of Australia treatment, not the least of which is the recircumscription of a number of species and the recognition of a great many more new species, particularly from Queensland where the genus had been undercollected and species boundaries were previously poorly known.
These changes have been incorporated in the interactive key produced here where 182 species are recognised compared with the earlier 117 species. There is now some inequality in species concepts with a narrower concept operating in those species examined by Bean when compared with the broader approach by Symon. This is understandable since the base-line, Australia-wide, studies by Symon were often conducted on inadequate material; the basic framework provided by Symon has now allowed others to make more in-depth studies of biology, morphology and DNA and further changes in species delimitation will undoubtedly occur.
Two species now treated as Lycianthes, L. shanesii and L. rantonnetii, have been included in the key to Solanum species. The apparently native L. shanesii was previously treated as a synonym of Capsicum annuum before being reinstated as a Solanum species with affinities to South American members of sect. Lycianthes. Bean transferred this species to Lycianthes in 2003. Subsequent work (Walsh & Hoot 2001) indicates that this species has close relationships with American species of Lycianthes, casting some doubt on its being native to Australia.
Symon, D.E. & Clarkson, J.R. (1985) The Reinstatement of Solanum shanesii F.Muell. section Lycianthes (Solanaceae) with discussion of its significance. Journal of the Adelaide Botanic Gardens 7: 201-206. Bean, A.R. (2003) New combinations in Lycianthes (Dunal) Hassl. (Solanaceae) for New Guinea and Australia. Austrobaileya 6(3): 568. B.M.Walsh & S.B.Hoot (2001). Phylogenetic relationships of Capsicum (Solanaceae) using DNA sequences from two noncoding regions:the chloroplast atpB-rbcL spacer region and nuclear waxy introns. Int. J. Plant Science 162: 1409-1418.
Also included in the Solanum key to species are tomato (Solanum lycopersicum or Lycopersicon esculentum) and tree tomato (Solanum betaceum or Cyphomandra betacea), both treated as the segregate genera in the 1982 Flora of Australia treatment.
Cyphomandra was separated from Solanum on the basis of few technical characters such as the thickening of the connective at the back of the anther. This separation from Solanum has long been questioned. Recent sequencing of DNA places Cyphomandra species clearly with Solanum. A monograph on this group of species as Cyphomandra may be found in L. Bohs Cyphomandra (Solanaceae), Flora Neotropica, Monograph 63 New York Bot. Gard. (1994) 1–176 and their transfer to Solanum in L. Bohs, Taxon, 44 (1995) 583–587.
Research publications since the Flora of Australia treatment
Overall classification of Solanum (see also Solanaceae Source)
Bohs, L. (2005). Major clades in Solanum based on ndhF sequences. In: Keating RC, Hollowell VC, Croat TB (eds) A Festschrift for William G. D’Arcy: The Legacy of a Taxonomist, Missouri Botanical Garden, St. Louis. Monogr. Syst. Bot. Missouri Bot. Gard. 104: 27–49.
Knapp, S. (2002). Solanum section Geminata (Solanaceae).(Flora neotropica; monograph 84.) New York Botanical Garden for the Organization for Flora Neotropica : New York. 404 pp.
Levin, R.A., Watson, K. & Bohs L. (2005). A four-gene study of evolutionary relationships in Solanum section Acanthophora. American J. Botany 92: 603-612.
Levin, RA, Myers, NR & Bohs L. (2006). Phylogenetic relationships among the “spiny solanums” (Solanum subgenus Leptostemonum, Solanaceae). American J. Botany 93: 157-169.
Martine, C.T., Vanderpool, D., Anderson, Gregory J. & Les, D.H. (2006). Phylogenetic relationships of andromonoecious and dioecious Australian species of Solanum subgenus Leptostemonum section Melongena: inferences from ITS Sequence Data. Systematic Botany 31(2): pp. 410–420
Stafford P. & Knapp, S. (2006) Pollen morphology and systematics of the zygomorphic-flowered nightshades (Solanaceae; Salpiglossidae sensu D'Arcy, 1978 and Cestroideae sensu D'Arcy, 1991, pro parte): A review. Systematics & Biodiversity 4: 173-201
Weese, T.L. & Bohs, L. (2007). A three-gene phylogeny of the genus Solanum (Solanacaea). Systematic Botany 32: 445-463.
Welman, W.G. (2003). The genus Solanum (Solanaceae) in southern Africa: subgenus Leptostemonum, the introduced sections Acanthophora and Torva. Bothalia 33: 1–18.
Whalen, M.D. (1984). Conspectus of Species Groups in Solanum subgenus Leptostemonum. Gentes Herbarum 12(4): 179–282.
Whalen, M.D., Costich, D.E. & Heiser, C.B. (1981). Taxonomy of Solanum Section Lasiocarpa. Gentes Herbarum 12(2): 41–129.
Australian classification
Bean, A.R. (2001). A revision of Solanum brownii Dunal (Solanaceae) and its allies. Telopea 9: 639-661.
Bean, A.R. (2002). The identity of “Solanum adenophorum” in New South Wales and Victoria. Australian Systematic Botany Society Newsletter 111: 6.
Bean, A.R. (2002). New prostrate taxa in Solanum subg. Leptostemonum (Dunal in DC.)Bitter (Solanaceae) from eastern Australia. Austrobaileya 6: 639-816.
Bean, A.R. (2004). The taxonomy and ecology of Solanum subg. Leptostemonum (Dunal)Bitter (Solanaceae) in Queensland and far north-eastern New South Wales, Australia. Austrobaileya 6: 639-816.
Brennan, K., Martine, C.T. & Symon, D.E. (2006). Solanum sejunctum (Solanaceae), a new functionally dioecious species from Kakadu National Park, Northern Territory, Australia. He Beagle, Records of the Museums and Art Galleries of the Northern Territory 22: 1-7.
Symon D.E. (1981). A revision of the genus Solanum in Australia. Journal of the Adelaide Botanic Gardens 4: 1-367.
Symon D.E. (1987). Placentation patterns and seed numbers in Solanum (Solanaceae) fruits. Journal of the Adelaide Botanic Gardens 10: 179-99.
Symon D.E. (1995). Four new species of Solanum L. (Solanaceae) from south east Queensland. Austrobaileya 4(3): 429–37.
Symon, D.E. (2001). Solanum oligandrum (Solanaceae), a new species from the Great Sandy Desert, Western Australia. Nuytsia 13(3): 537–41.
Floral biology and pollination of Solanum
Most species of Solanum are “buzz” pollinated i.e. they require vibrations produced by visiting insects to release the pollen; such pollination is characteristic of many species where anthers open by terminal pores – they function like “salt shakers” when vibrated (see http://en.wikipedia.org/wiki/Buzz_pollination or http://gears.tucson.ars.ag.gov/ic/buzzpol/buzzpol.html for further discussion of this phenomenon).
There has been pressure to introduce bumble bees to Australia because of the increased fruit set which can be achieved in tomatoes and capsicums by the bumblebees promotion of pollination in the glass-house (see www.bio-bee.com/english/bombus/bombus.htm) – there have also been attempts to harness the native blue-banded bee for the same role. One viewpoint from the Australian tomato growers can be seen at http://www.hydroponics.com.au/back_issues/issue89.html while the opposing viewpoint is put at www.zeta.org.au/~anbrc/bumblebeeharm.html
Pollination in a species of Solanum previously referred to Cyphomandra is discussed and illustrated by Carol Gracie (1993) on the New York Botanical Garden site at http://www.nybg.org/bsci/french_guiana/cypho.html One of the main distinctions between Cyphomandra and Solanum is the enlarged anther connective of the former. It is postulated that the connective is supplying reward to visiting bees in the form of aromatic compounds. Further information can be found in Sazima et al. (1993).
Symon (1979) reviewed the literature on the pollination of Solanum species and the importance of specialized pollinators. A discussion of north-western Australian species of Solanum and the roles of their various bee pollinators can be found in Anderson & Symon (1988); some of the pollinators extract pollen by other means than buzzing.
While there are undoubtedly a number of papers of floral studies of individual species e.g. observations in Solanum torvum (Hossain 1973) where style length was found to be dependent on where a flower is in the inflorescence, the main focus of Australian studies has usually been in comparisons of the hermaphrodite, andromonoecious and functionally dioecious species of northern Australia (Symon 1979; Anderson & Symon 1989). Andromonoecy in Solanum was surveyed by Whalen & Costich (1986), resource investment in male and hermaphrodite flowers was investigated by Solomon (1986) and pollen morphology and functional dioecy by Knapp et al. (1998).
A comparison of the anthers and the corolla for the presence of scent was conducted for a number of Solanaceous species by D’Arcy et al. (1990); anthers were often found to carry a scent, whereas the corolla does not.
Anderson, G.J. & Symon, D.E. (1985). Extrafloral nectaries in Solanum. Biotropica 17: 40-45.
Anderson, G.J. & Symon, D.E. (1988). Insect foragers on Solanum flowers in Australia. Annals Missouri Bot. Gard. 75: 842-852.
Anderson, G.J. & Symon, D.E. (1989). Functional dioecy and andromonoecy in Solanum. Evolution 43: 204-219.
D’Arcy, W.G., D’Arcy, N.S. & Keating, R.C. (1990). Scented anthers in Solanaceae. Rhodora 92: 50-53.
Diggle, P.K. and Miller, J.S. (2004). Architectural effects mimic floral sexual dimorphism in Solanum (Solanaceae). Am. J. Bot. 91: 2030-2040.
Gracie, C. (1993). Pollination of Cyphomandra endopogon var. endopogon (Solanaceae) by Eufriesea spp. (Euglossini) in French Guiana. Brittonia 45(1): 39-46. Available at http://www.nybg.org/bsci/french_guiana/cypho.html
Hossain M. (1973). Observations on stylar heteromorphism in Solanum torvum Sw. (Solanaceae). Botanical Journal of the Linnean Society 66: 291-301.
Knapp, S., Persson, V. &. Blackmore, S. (1998). Pollen morphology and functional dioecy in Solanum (Solanaceae). Pl. Syst. Evol. 210: 113-139, f. 1-8.
Miller, J.S. and Diggle, P.K (2003). Diversification of andromonoecy in Solanum section Lasiocarpa (Solanaceae): the roles of phenotypic plasticity and architecture. Am. J. Bot. 90: 707-715.
Sazima, M., S. Vogel, A. Cocucci & G. Hausner. (1993). The perfume flowers of Cyphomandra (Solanaceae): Pollination by euglossine bees, bellows mechanism, osmophores, and volatiles. Pl. Syst. Evol. 187: 51-88.
Solomon, B.P. (1986). Sexual allocation and andromonoecy: resource investment in male and hermaphrodite flowers of Solanum carolinense (Solanaceae). American J. Bot. 73: 1215-1221.
Symon, D.E. (1979). Sex forms in Solanum (Solanaceae) and the role of pollen collecting insects. In J.G.Hawkes, R.N.Lester & A.D.Skelding (eds). The Biology and Taxonomy of the Solanaceae. (Academic Press: London). pp. 385-397.
Whalen , M. & Costich, D.E. (1986). Andromonoecy in Solanum. In D’Arcy, W.G. (ed.) (1986). Solanaceae II, Biology and Systematics. (Columbia University Press, New York).
Dispersal in Solanum in Australia
Symon, D.E. (1979). Fruit diversity and dispersal in Solanum in Australia. J. Adelaide Bot. Gard.1: 321-331.
Hair types in Solanum
Studies by Bean (2004) and by South American botanists, Granada-Chacón & Benítez de Rojas (2005) indicate that trichome morphology can be used to separate species. Bean has attempted to put the description of hair types and their density on to a more objective basis providing an account of the definitions he used for the compilation of his species descriptions in his account of subg. Leptostemonum. While based on the previous work of Seithe (1979), Bean does provide an excellent background to the sort of characters which need to be measured for each of the hair types, but more particularly for the stellate hairs. Detectable characteristics previously not used because of difficulty in expressing them have been placed on a quantitative basis and found to be useful in the separation of taxa. For anyone developing new species descriptions of Solanum in Australia (or elsewhere) these pages are required reading.
Granada-Chacón, W.A. & Benítez de Rojas, C.E. (2005). Morfología de tricomas foliares en especies de Solanum sección Acanthophora (Solanaceae), presentes en Venezuela. Sida 21: 1675-1694.
Seithe, A. (1979). Hair types as taxonomic characters in Solanum. In J.G.Hawkes et al. The Biology and Taxonomy of the Solanaceae. (Academic Press for Linnean Society of London: London). pp. 307-19.
Seithe, A. & Anderson, G.J. (1982). Hair morphology and the Relationships of Species in Solanum sect. Basarthrum, Plant Systematics and Evolution 139: 229–56.
Key to species
All of the new taxa and the recircumscriptions have been taken into account in the interactive key to the species produced here and there is in addition another interactive key to species for Eastern Australia by Bean on the DELTA site at http://delta-intkey.com/solanum/www/ident.htm.
A dichotomous key and a synoptic key to the 90 species of Solanum subg. Leptostemonum in Queensland and far north-eastern New South Wales can be found in Bean's treatment of this group in Austrobaileya 6: 639-816 (2004).
The Lucid key does contain three Solanum keys
- a key to the subgenera of Solanum occurring in Australia
- a key to the groupings in the largest subgenus in Australia, subgenus Leptostemonum
- a key to all of the species of Solanum in Australia
In using the key you may choose to go straight to the key to all species, or you may wish to work out which of the higher groupings your species belongs to and thus more quickly reduce the choices in key 3.