Salvia () is the largest genus of plants in the sage family Lamiaceae, with just under 1,000 species of shrubs, herbaceous perennials, and annuals. Within the Lamiaceae, Salvia is part of the tribe Mentheae within the subfamily Nepetoideae. One of several genera commonly referred to as sage, it includes two widely used herbs, Salvia officinalis (common sage, or just "sage") and Salvia rosmarinus (rosemary, formerly Rosmarinus officinalis). The genus is distributed throughout the Old World and the Americas (over 900 total species), with three distinct regions of diversity: Central America and South America (approximately 600 species); Central Asia and the Mediterranean (250 species); Eastern Asia (90 species).
Etymology
The name Salvia derives from Latin salvia (sage), from salvus (safe, secure, healthy), an adjective related to salūs (health, well-being, prosperity or salvation), and salvēre (to feel healthy, to heal). 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 borrowed from Old French sauge, from Latin salvia (the source of the botanical name). When used without modifiers, the name "sage" generally refers to Salvia officinalis ("common sage" or "culinary sage"), although 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.
Description Salvia species include annual, biennial, or perennial herbaceous plants, 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—in some species the bracts 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. Many members of Salvia 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.
Staminal lever mechanism
The defining characteristic of the genus Salvia is the unusual pollination mechanism. It is central to any investigation into the systematics, species distribution, or pollination biology of Salvia. It consists of two stamens (instead of the typical four found in other members of the tribe Mentheae) and the two thecae on each stamen are separated by an elongate connective which enables the formation of the lever mechanism. Sprengel (1732) was the first to illustrate and describe the nototribic (dorsal) pollination mechanism in Salvia. When a pollinator probes a male stage flower for nectar, (pushing the posterior anther theca) the lever causes 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. In older, female stage flowers, the stigma is bent down 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 is generic and selected to be easily released by many bird and bee pollinators of varying shapes and sizes. The lever arm can be specialized to be different lengths so that the pollen is deposited on different parts of the pollinator's body. For example, if a bee went to one flower and pollen was deposited on the far back of her body, but then it flew to another flower where the stigma was more forward (anterior), pollination could not take place. This can result in reproductive isolation from the parental population and new speciation can occur. It is believed that the lever mechanism is a key factor in the speciation, adaptive radiation, and diversity of this large genus.
Taxonomy
History George Bentham was first to give a full monographic account of the genus in 1832–1836, and based his classifications on staminal morphology. 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.
Subdivision
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:
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