| Salvia | |
|---|---|
| Meadow Sage (S. pratensis) | |
| Scientific classification | |
| Kingdom: | Plantae |
| (unranked): | Angiosperms |
| (unranked): | Eudicots |
| (unranked): | Asterids |
| Order: | Lamiales |
| Family: | Lamiaceae |
| Subfamily: | Nepetoideae |
| Tribe: | Mentheae |
| Genus: | Salvia L.[1] |
| Species | |
Salvia is the largest genus of plants in the mint family, Lamiaceae, with approximately 700-900 species of shrubs, herbaceous perennials, and annuals.[2][3] It is one of several genera commonly referred to as sage. When used without modifiers, sage generally refers to Salvia officinalis ("common sage"); however, it is used with modifiers to refer to any member of the genus. The ornamental species are commonly referred to by their genus name Salvia.
The genus is distributed throughout the Old World and the Americas, with three distinct regions of diversity: Central and South America (approx. 500 species); Central Asia and Mediterranean (250 species); Eastern Asia (90 species).[4]
Contents |
Salvia derives from the Latin salvere ("to save"), referring to the long-held belief in the herb's healing properties. Pliny the Elder was the first author known to describe a plant called "Salvia" by the Romans, likely describing the type species for the genus Salvia, Salvia officinalis. The common modern English name sage derives from Middle English sawge, which was loaned from Old French sauge, and like the botanical name, stems from Latin salvere.[5][6]
Salvia species include annual, biennial, or perennial herbs, along with woody subshrubs. The stems are typically angled like other members in Lamiaceae. The leaves are typically entire, but sometimes toothed or pinnately divided. The flowering stems bear small bracts, dissimilar to the basal leaves, though in some species they are ornamental and showy.
The flowers are produced in racemes, or panicles, and generally produce a showy display with flower colors ranging from blue to red, with white and yellow less common. The calyx is normally tubular or bell shaped, without bearded throats, and divided into two parts or lips, the upper lip entire or three-toothed, the lower two-cleft. The corollas are often claw shaped and are two-lipped. The upper lip is usually entire or three-toothed. The lower lip typically has two lobes. The stamens are reduced to two short structures with anthers two-celled, the upper cell fertile, and the lower imperfect. The flower styles are two-cleft. The fruits are smooth ovoid or oblong nutlets and in many species they have a mucilaginous coating.[7]
Many salvias have trichomes (hairs) growing on the leaves, stems, and flowers, which help to reduce water loss in some species. Sometimes the hairs are glandular and secrete volatile oils that typically give a distinct aroma to the plant. When the hairs are rubbed or brushed, some of the oil-bearing cells are ruptured, releasing the oil. This often results in the plant being unattractive to grazing animals and some insects.[2]
George Bentham was first to give a full monographic account of the genus in 1832-1836, and based his classifications on staminal morphology.[8] The defining characteristic of the genus Salvia is the unusual pollination mechanism, which consists of two stamens (instead of the typical four found in other members of the tribe Mentheae) and the way the two stamens are connected to form a lever. When a pollinator enters the flower for nectar, the lever activates causing the stamens to move and the pollen to be deposited on the pollinator. When the pollinator withdraws from the flower, the lever returns the stamens to their original position. As the pollinator enters another flower of the same species, the stigma is placed in a general location that corresponds to where the pollen was deposited on the pollinator's body. The lever of most Salvia species is not specialized for a single pollinator, but generic and selected to be easily released by many bird and bee pollinators of varying shapes and sizes.[9] It is believed that this is a key factor in the speciation of this large group of diverse plants.[10]
Bentham's work on classifying the family Labiatae (Labiatarum Genera et Species (1836)) is still the only comprehensive and global organization of the family. While he was clear about the integrity of the overall family, he was less confident about his organization of Salvia, the largest genus in Labiatae (also called Lamiaceae). Based on his own philosophy of classification, he wrote that he "ought to have formed five or six genera" out of Salvia. In the end, he felt that the advantage in placing a relatively uniform grouping in one genus was "more than counterbalanced by the necessity of changing more than two hundred names." At that time there were only 291 known Salvia species.[2]
Bentham eventually organized Salvia into twelve sections (originally fourteen), based on differences in corolla, calyx, and stamens. These were placed into four subgenera that were generally divided into Old World and New World species:
His system is still the most widely studied classification of Salvia, even though more than 500 new species have been discovered since his work. Other botanists have since offered modified versions of Bentham's classification system, while botanists in the last hundred years generally do not endorse Bentham's system.[2]
It was long assumed that Salvia's unusual pollination and stamen structure had evolved only once, and that therefore Salvia was monophyletic, meaning that all members of the genus evolved from one ancestor. However, through DNA sequencing it now appears that somewhat different versions of this lever mechanism have evolved in the tribe Mentheae, and at least three different times within Salvia, making the genus clearly non-monophyletic. The genus may therefore consist of as many as three different clades, or branches.[4][11]
The description of individual species within Salvia has undergone constant revision. Many species are similar to each other, and many species have varieties that have been given different specific names. There have been as many as 2,000 named species and subspecies. Over time, the number has been reduced to less than a thousand. A modern and comprehensive study of Salvia species was done by Gabriel Alziar, in his Catalogue Synonymique des Salvia du Monde (1989) (World Catalog of Salvia Synonyms). He found that the number of distinct species and subspecies could be reduced to less than 700.[2][12]
Many species are used as herbs, as ornamental plants (usually for flower interest), and sometimes for their ornamental and aromatic foliage. A selection of some well known species is below.
Salvia species are used as food plants by the larvae of some Lepidoptera (butterfly and moth) species including the bucculatricid leaf-miner Bucculatrix taeniola which feeds exclusively on the genus and the Coleophora case-bearers C. aegyptiacae, C. salviella (both feed exclusively on S. aegyptiaca), C. ornatipennella and C. virgatella (both recorded on S. pratensis).