Solanum

''Solanum'' is a large and diverse genus of flowering plants, which include three food crops of high economic importance: the potato, the tomato and the eggplant (aubergine, brinjal). It is the largest genus in the nightshade family Solanaceae, comprising around 1,500 species. It also contains the so-called horse nettles (unrelated to the genus of true nettles, '' Urtica''), as well as numerous plants cultivated for their ornamental flowers and fruit.

''Solanum'' species show a wide range of growth habits, such as annuals and perennials, vines, subshrubs, shrubs, and small trees. Many formerly independent genera like '' Lycopersicon'' (the tomatoes) and '' Cyphomandra'' are now included in ''Solanum'' as subgenera or sections. Thus, the genus today contains roughly 1,500–2,000 species.

Name

The generic name was first used by Pliny the Elder (AD 23–79) for a plant also known as , most likely ''S. nigrum''. Its derivation is uncertain, possibly stemming from the Latin word , meaning "sun", referring to its status as a plant of the sun.

Species having the common name "nightshade"

The species most commonly called nightshade in North America and Britain is '' Solanum dulcamara'', also called bittersweet or woody nightshade (so-called because it is a ( scandent) shrub). Its foliage and egg-shaped red berries are poisonous, the active principle being solanine, which can cause convulsions and death if taken in large doses. Black nightshade ('' Solanum nigrum'') is also generally considered poisonous, but its fully-ripened fruit and foliage are cooked and eaten in some areas. Deadly nightshade (''Atropa belladonna'') belongs, like ''Solanum'', to subfamily Solanoideae of the nightshade family, but, unlike that genus, is a member of tribe Hyoscyameae (''Solanum'' belongs to tribe Solaneae). The chemistry of '' Atropa'' species is very different from that of Solanum species and features the very toxic tropane alkaloids, the best-known of which is atropine.

Food crops

Most parts of the plants, especially the green parts and unripe fruit, are poisonous to humans (although not necessarily to other animals), but many species in the genus bear some edible parts, such as fruits, leaves, or tubers. Three crops in particular have been bred and harvested for consumption by humans for centuries, and are now cultivated on a global scale:
* Tomato, ''S. lycopersicum''
** Tomato varieties are sometimes bred from both ''S. lycopersicum'' and wild tomato species such as ''S. pimpinellifolium'', ''S. peruvianum'', ''S. cheesmanii'', ''S. galapagense'', ''S. chilense'', etc. (such varieties include—among others—Bicentennial, Dwarf Italian, Epoch, Golden Sphere, Hawaii, Ida Red, Indigo Rose, Kauai, Lanai, Marion, Maui, Molokai, Niihau, Oahu, Owyhee, Parma, Payette, Red Lode, Super Star, Surecrop, Tuckers Forcing, V 121, Vantage, Vetomold, and Waltham.)
* Potato, ''S. tuberosum'', fourth largest food crop.
** Less important but cultured relatives used in small amounts include ''S. stenotomum, S. phureja, S. goniocalyx, S. ajanhuiri, S. chaucha, S. juzepczukii, S. curtilobum''.
* Eggplant (also known as brinjal or aubergine), ''S. melongena''

Other species are significant food crops regionally, such as Ethiopian eggplant or gilo ('' S. aethiopicum''), naranjilla or lulo (''S. quitoense''), Turkey berry ('' S. torvum''), pepino or pepino melon ('' S. muricatum''), Tamarillo ('' S. betaceum''), wolf apple ('' S. lycocarpum''), garden huckleberry (''S. scabrum'') and " bush tomatoes" (several Australian species).

Ornamentals

The species most widely seen in cultivation as ornamental plants are:
*'' S. aviculare'' (kangaroo apple)
*'' S. capsicastrum'' (false Jerusalem cherry, winter cherry)
*'' S. crispum'' (Chilean potato tree)
*'' S. laciniatum'' (kangaroo apple)
*'' S. laxum'' (potato vine)
*'' S. pseudocapsicum'' (Christmas cherry, winter cherry)
*'' S. rantonnetii'' (blue potato bush)
*'' S. seaforthianum'' (Italian jasmine, St. Vincent lilac)
*'' S. mauritianum'' (woolly nightshade, earleaf nightshade)
*'' S. wendlandii'' (paradise flower, potato vine)

Medicine

Poisonings associated with certain species of ''Solanum'' are not uncommon and may be fatal. However, several species are locally used in folk medicine, particularly by native people who have long employed them.

Ecology

''Solanum'' species are used as food plants by the larvae of some Lepidoptera species (butterflies and moths) – see list of Lepidoptera that feed on ''Solanum''.

Systematics

The genus was established by Carl Linnaeus in 1753. Its subdivision has always been problematic, but slowly some sort of consensus is being achieved.

The following list is a provisional lineup of the genus' traditional subdivisions, together with some notable species. Many of the subgenera and sections might not be valid; they are used here provisionally as the phylogeny of this genus is not fully resolved yet and many species have not been reevaluated.

Cladistic analyses of DNA sequence data suggest that the present subdivisions and rankings are largely invalid. Far more subgenera would seem to warrant recognition, with ''Leptostemonum'' being the only one that can at present be clearly subdivided into sections. Notably, it includes as a major lineage several members of the traditional sections ''Cyphomandropsis'' and the old genus '' Cyphomandra''.

A recent study built a densely sampled species-level phylogeny for ''Solanum'' comprising 60% of all accepted species based on full plastome dataset and nuclear target-capture data. While the taxonomic framework of ''Solanum'' remained stable, researchers observed gene tree conflicts and discordance between phylogenetic trees generated from the target-capture and plastome datasets. The latter corresponded to regions with short internodal branches, and network analysis and polytomy tests suggested the backbone is composed of three polytomies found at different evolutionary depths. The strongest area of discordance, near the crown node of Solanum, was found to be a hard polytomy. Currently, the most likely explanation for the discordance along the backbone of ''Solanum'' is due to incomplete lineage sorting (ILS) caused by rapid speciation. Presence of short internal branches is typical of ILS in lineages with large population sizes and high mutation rates. This fits with the biology of ''Solanum'' in general, which is typically known to contain “weedy”, disturbance-loving pioneer species resilient to change. Many species are known to have large geographical ranges and ecological amplitude. Some of the weedy characteristics found in these species include the ability to improve fitness and defense traits in response to disturbance, as well as having allelopathic properties which allow them to establish themselves to the detriment of native vegetation. If such characteristics were present in ancestral Solanum, they could have promoted rapid speciation across the globe, followed by rapid morphological evolution and speciation within areas. The patterns observed here could possibly be the result of three major rapid speciation “pulses” across the evolutionary history of Solanum. The idea of an ecologically opportunistic ancestor is supported by the tendency of many of the major clades to occupy periodically highly stressed and disturbed habitats, including flooded varzea forests, hyper-arid deserts, and highly disturbed and dynamic open mid-elevation Andean montane habitats, where landslides are among the most common areas where many of the species are found. The idea that well-supported and fully bifurcating phylogenies are a requisite for evolutionary studies is built on the premise that such trees are the accurate way of representing evolution. The shift in systematics from “tree”- to “bush”-like thinking, where polytomies and reticulate patterns of evolution are considered as acceptable or real, comes from the accumulation of studies finding similar unresolvable phylogenetic nodes, despite using different large-scale genomic sampling strategies and various analytical methods. We argue that acknowledging and embracing polytomies and reticulation is crucial if we are to design research programs aimed at understanding the biology of large and rapidly radiating lineages, such as the large and economically important Solanum.

Subgenus ''Bassovia''

Section ''Allophylla''
* '' Solanum granuloso-leprosum''
Section ''Cyphomandropsis''
* ''Solanum glaucophyllum'' Desf. – Waxy-leaved nightshade
Section ''Pachyphylla''
* ''Solanum betaceum'' Cav. – Tamarillo
* ''Solanum exiguum''
* '' Solanum roseum''

Subgenus ''Leptostemonum''

Section ''Acanthophora''
* '' Solanum aculeatissimum'' Jacq. – Indian nightshade
* ''Solanum atropurpureum'' Schrank – Five-minute plant
* '' Solanum capsicoides'' – Cockroach berry, ''polohauaiʻi'' ( Polynesian)
* '' Solanum mammosum'' – Nipplefruit, titty fruit, cow's udder, "apple of Sodom"
* ''Solanum palinacanthum'' Dunal
* '' Solanum viarum'' Dunal – Tropical soda apple
Section ''Androceras'': 12 spp.
* Series ''Androceras''
* Series ''Violaceiflorum''
* Series ''Pacificum''
Section ''Anisantherum''

Section ''Campanulata''

Section ''Crinitum''

Section ''Croatianum''

Section ''Erythrotrichum''
* ''Solanum robustum'' H.L.Wendl. – Shrubby nightshade
Section ''Graciliflorum''

Section ''Herposolanum''
* '' Solanum wendlandii'' Hook.f. – Giant potatocreeper
Section ''Irenosolanum''
* '' Solanum incompletum'' Dunal – ''Pōpolo kū mai'' (Hawaii)
* ''Solanum nelsonii'' Dunal – Nelson's horsenettle, ''Ākia'' (Hawaii)
* '' Solanum sandwicense'' Hook. & Arn. – Hawaiian horsenettle, ''Pōpoloaiakeakua'' (Oahu, Kauai)
Section ''Ischyracanthum''

Section ''Lasiocarpa''
* '' Solanum lasiocarpum'' Dunal
* '' Solanum pseudolulo'' – ''lulo de perro'' (Colombia)
* '' Solanum quitoense'' – '' lulo'' ( Colombia), ''naranjilla'' (Ecuador)
* '' Solanum sessiliflorum'' – Cocona
Section ''Melongena''
* ''Solanum aculeastrum'' – Soda apple, sodaapple nightshade, goat apple, poison apple, "bitter-apple"
* ''Solanum campechiense'' – Redberry nightshade
* '' Solanum carolinense'' – Carolina horsenettle, radical weed, sand brier, devil's tomato, "bull nettle", "tread-softly", "apple of Sodom", "wild tomato" (southeastern United States)
* ''Solanum cataphractum'' (northern Western Australia, including Coronation Island)
* '' Solanum citrullifolium'' A.Braun – Watermelon nightshade (southern United States)
* ''Solanum dimidiatum'' Raf. – Torrey's nightshade
* '' Solanum elaeagnifolium'' – Silver-leaved nightshade, prairie berry, silverleaf nettle, white horsenettle, silver nightshade, "bull-nettle", "trompillo" (Spanish); Silver-leaf bitter-apple, ''satansbos'' (South Africa)
* '' Solanum heterodoxum'' Dunal – Melon-leaved nightshade
* '' Solanum incanum'' L.
* ''Solanum linnaeanum'' – Devil's apple, "apple of Sodom"
* ''