Artemisia (genus)

''Artemisia'' ( ) is a large, diverse genus of plants belonging to the daisy family, Asteraceae, with almost 500 species. Common names for various species in the genus include mugwort, wormwood, and sagebrush.

Some botanists split the genus into several genera, but DNA analysis does not support the maintenance of the genera ''Crossostephium'', ''Filifolium'', ''Neopallasia'', ''Seriphidium'', and ''Sphaeromeria''; three other segregate genera—''Stilnolepis'', ''Elachanthemum'', and ''Kaschgaria''—are maintained by this evidence. Occasionally, some of the species are called sages, causing confusion with the ''Salvia'' sages in the family Lamiaceae.

''Artemisia'' comprises hardy herbaceous plants and shrubs, which are known for the powerful chemical constituents in their essential oils. ''Artemisia'' species grow in temperate climates of both hemispheres, usually in dry or semiarid habitats. Notable species include '' A. vulgaris'' (common mugwort), '' A. tridentata'' (big sagebrush), '' A. annua'' (sagewort), '' A. absinthium'' (wormwood), ''A. dracunculus'' ( tarragon), and '' A. abrotanum'' (southernwood), and ''A. herba-alba'' (white wormwood). The leaves of many species are covered with white hairs.

Most species have strong aromas and bitter tastes from terpenoids and sesquiterpene lactones, which discourage herbivory, and may have had a selective advantage. The small flowers are wind-pollinated. ''Artemisia'' species are used as food plants by the larvae of a number of Lepidoptera species.

Taxonomy

The genus was erected by Carl Linnaeus in 1753. The name ''Artemisia'' derives from the Greek goddess Artemis (Roman Diana), the namesake of Greek Queens Artemisia I and II. A more specific reference may be to Artemisia II of Caria, a botanist and medical researcher (also a queen and naval commander), who died in 350  BCE.

Classification

Classification of ''Artemisia'' is difficult. Divisions of ''Artemisia'' prior to 2000 into subgenera or sections have not been backed up by molecular data, but much of the molecular data, as of 2006, are not especially strong. The following identified groups do not include all the species in the genus.

Subgenera ''Artemisia'' and ''Absinthium''

Subgenera ''Artemisia'' and ''Absinthium'' are sometimes, but not always, considered the same. Subgenus ''Artemisia'' (originally ''Abrotanum'' Besser) is characterized by a heterogamous flower head with female outer florets and hermaphrodite central florets, and a fertile, glabrous receptacle. ''Absinthium'' DC, though sometimes merged with subgenus ''Artemisia'' is characterized by heterogamous flower head with female outer florets and hermaphrodite central florets, and a fertile, hairy receptacle. Generally, previously proposed monotypic and non-monophyletic subgenera have been merged with the subgenus ''Artemesia'' due to molecular evidence. For example, in 2011 using ribosomal DNA analysis of their own and a review of molecular data (such as ITS sequence analysis) of others, S. Garcia and colleagues argued that it was logical to rename several ''Sphaeromeria'' and ''Picrothamnus'' (formerly designated sister genera to ''Artemisia'') species as ''Artemisia'', as well as to revert some ''Sphaeromeria'' species back to ''Artemisia'', where they had been categorized previously. Part of this was due to research by Watson and colleagues, who found that the four subgenera were not monophyletic except for ''Dracunculus,'' after analyzing and matching the internal transcribed spacers of nuclear ribosomal DNA from many ''Seriphidium'' and ''Artemisia'' species, and the related genera ''Arctanthemum'' and ''Dendranthema''. The authors concluded that inflorescence morphology is not alone reliable for categorizing the genus or some subgenera, as qualities that previously demarcated them (such as homogamous, discoid, ray-less inflorescences) seemed to have undergone paralleled evolution up to seven times. ''Picrothamnus'' Nutt. ("bud sage"), now considered ''Artemisia spinescens'' and ''Sphaeromeria'' Nutt. ("chicken sage") are some examples, both endemic to North America.

''Tridentatae''

Section ''Tridentatae'' consists of eleven to thirteen species of coarse shrubs often known colloquially as "sagebrushes", which are very prominent parts of the flora in western North America. In some classifications, they have previously been considered part of the genus or subgenus ''Seriphidium'', although recent studies have contested this lineage to Old World species. ''Tridentatae'' was first articulated as a section by Rydberg in 1916, and it was not until McArthur et al. in 1981 that ''Tridentatae'' was elevated to a separate subgenus from ''Seriphidium''. The principal motive for their separation was geographical distribution, chemical makeup, and karyotype. Much of the debate surrounding Tridentatae is phytogeographic, thus habitat and geography are frequently cited when understanding the evolution of this endemic North American subgenus. Evolutionary cycles of wet and dry climates encouraged "diploid and polyploid races which are morphologically similar if not indistinguishable" (McArthur 598).

Autopolyploidy among plants is not uncommon, however ''Tridentatae'' exhibits a remarkable amount of chromosomal differences at the population level, rather than the taxon level. This contributes to the difficulty in determining ''Tridentatae's'' phylogeny. The subgenus' relative homogeneity within ploidies has enabled it to habitually hybridize and backcross, resulting in a high degree of genetic variation at the population level rather than the taxon level. For instance, some articles suggest that to be monophyletic, section ''Tridentatae'' should exclude '' Artemisia bigelovii'' and '' A. palmeri''. and include ''A. pygmaea'' and ''A. rigida''. These results were supported by extensive chloroplast DNA (cpDNA) and nrDNA sequencing which departed from prior morphological, anatomical, and behavioral data.

Traditional lineages within ''Tridentatae'' were proposed on the basis of leaf morphology, habitat preference, and the ability to leaf-sprout, among other morphological and behavioral characteristics. For instance, sagebrush in the ''A. tridentata'' lineage have tridentate leaves, live in especially arid habitats, and are unable to root-sprout. This method of delimitation is problematic for species that do not fully adhere to the characteristics of a given lineage. The dry habitat and the presence of interxylary cork has often made the case for ''Tridentatae'' as a subgenus of its own, and there is some ribosomal molecular evidence of a "''Tridentatae'' core" group for the subgenus. In 2011, Garcia and colleagues proposed enlarging ''Tridentatae'' and organized it into the sections ''Tridentatae'', ''Nebulosae'', and ''Filifoliae'' based on previous research establishing relationships via ribosomal and nuclear DNA.

Intergrading forms are particularly common in recently radiated subgenera such as ''Tridentatae'', given their frequent reversals and convergent evolution. Global reviews of ''Artemisia'' using ITS analysis support the hypothesis that ''Tridentatae'' has independent origins from Old World ''Seriphidium'' These findings were compared with capitula morphology, challenging past assumptions based on floral characteristics. To better understand the rapid diversification and radiation relative to Old World ''Artemisia'', a closer study of Beriginian or Arctic species may provide missing links.

*'' Artemisia tridentata''
*'' Artemisia cana''
*'' Artemisia nova''
*'' Artemisia rigida''
*'' Artemisia arbuscula''
*'' Artemisia longiloba''
*'' Artemisia tripartita''
*'' Artemisia pygmaea''
*'' Artemisia rothrockii''

Section ''Tridentatae'' includes above species with the exception of ''A. longiloba'', which is treated as a subspecies of ''A. arbuscula''. Section ''Nebulae'' includes '' A. californica'', '' A. nesiotica'', and '' A. filifolia''.

''Seriphidium''

The Old World species which different classifications put into the genus or subgenus ''Seriphidium'' consist of about 125 species native to Europe and temperate Asia, with the largest number of species in Central Asia. Some classifications, such as that of the Flora of North America, exclude any New World plants from ''Seriphidium''. They are herbaceous plants or small shrubs.

''Seriphidium'' Besser was morphologically categorized by a homogamous flower head with all hermaphrodite florets and fertile and glabrous receptacle. ''Tridentatae'' was originally categorized as within ''Seriphidium'' due to floral, inflorescence, and leaf morphological similarities, until McArthur et al.'s analysis in 1981, which explained these similarities as convergent evolution. Old World ''Seriphidium'', with 125 species native to Europe and temperate Asia, was a previous classification of ''Seriphidium''. North American or "New World" ''Seriphidium'' and Old World ''Seriphidium''. North American ''Seriphidium'' were later placed into ''Tridentatae'' Rydb due to geographical distribution, growth habit, and karyotypic and chemotaxonomic similarities (such as presence of certain terpenols).

Subgenus ''Dracunculus''

One group which is well-supported by molecular data is subgenus ''Dracunculus''. It consists of 80 species found in both North America and Eurasia, of which the best-known is perhaps '' Artemisia dracunculus'', the spice tarragon.

''Dracunculus'' Besser. has historically been characterized morphologically by a heterogamous flower head with female outer florets and hermaphrodite central florets, but with a female-sterile, glabrous receptacle. ''Dracunculus'' is the most supported and resolved subgenus of ''Artemisia'', which includes ''Artemisia'' ''dracunculus'' L., known as the cooking spice tarragon. Chloroplast and ribosomal DNA sequence analysis in 2011 supported monophyly with two clades, one of which includes some North American endemic species as well as most species of Europe and Asia, while the second clade includes just ''A. salsoloides'' and ''A. tanaitica'', found in Eastern Europe and Siberia to the Western Himalayas. This study places ''Dracunculus'' as one of the more recent subgenera within Artemisia, situating ''A. salisoides'' more basally on the tree, with North American endemic groups such as the sagebrushes having derived on the other end of a split from a common ancestor with ''Dracunculus''. Formerly proposed genera ''Mausolea'', ''Neopallasia'' and ''Turaniphytum'' are now argued to be within the subgenus ''Dracunculus'' due to ribosomal and chloroplast DNA evidence, with further species resolved as sister groups to ''Dracunculus'' due to phytochemical relationships.

Species

, Plants of the World Online accepted almost 500 species.

*'' Artemisia abrotanum'' L. – southernwood, southern wormwood, slovenwood, abrotanum, old-man, lad's love
*'' Artemisia absinthium'' L. – grand wormwood, absinthium
*'' Artemisia afra'' Jacq. ex Willd. – African wormwood, African sagebrush
*'' Artemisia alba'' Turra – camphor southernwood
*'' Artemisia aleutica'' Hultén – Aleutian wormwood
*'' Artemisia annua'' L. – annual wormwood, sweet sagewort, sweet Annie
*'' Artemisia arborescens'' L. – tree wormwood
*'' Artemisia arbuscula'' Nutt. – little sagebrush, low Sagebrush, black sage
*'' Artemisia arenaria'' DC.
*'' Artemisia argyi'' H.Lév. & Vaniot – Chinese mugwort
*'' Artemisia austriaca'' Jacq.
*'' Artemisia bhutanica'' Grierson & Spring.
*'' Artemisia biennis'' Willd. – biennial sagewort, biennial wormwood
*'' Artemisia bigelovii'' A.Gray – Bigelow sage, Bigelow sagebrush
*'' Artemisia caerulescens'' L.
*''Artemisia californica'' Less. – coastal sagebrush, California sagebrush
*'' Artemisia campestris'' L. – field wormwood, sand wormwood
*'' Artemisia cana'' Pursh – silver sagebrush
*'' Artemisia capillaris'' Thunb. – capillary wormwood, yin-chen wormwood
*'' Artemisia carruthii'' Wood ex Carruth. – Carruth sagewort, Carruth's sagebrush
*'' Artemisia chamaemelifolia'' Vill.
*'' Artemisia cina'' O.Berg & C.F.Schmidt – santonica, Levant wormseed
*'' Artemisia douglasiana'' Bess. – Douglas' mugwort, Douglas' sagewort, northwest mugwort
*'' Artemisia dracunculus'' L. – tarragon, silky wormwood
*'' Artemisia filifolia'' Torr. – sand sagebrush, sand-sage, silvery wormwood
*'' Artemisia franserioides'' Greene – ragweed sagebrush
*'' Artemisia frigida'' Willd. – fringed sagebrush, fringed-sage, prairie sagewort, estafiata
*'' Artemisia furcata'' Bieb. – forked wormwood
*'' Artemisia glacialis'' L. – glacier wormwood, alpine mugwort
*'' Artemisia glauca'' Pall. ex Willd.
*'' Artemisia globularia'' Cham. ex Bess. – purple wormwood
*'' Artemisia gmelinii'' Webb ex Stechmann – Gmelin's wormwood, Russian wormwood
*'' Artemisia gorgonum'' Webb
*'' Artemisia herba-alba'' Asso – white wormwood
*'' Artemisia indica'' Willd. – Indian wormwood
*'' Artemisia integrifolia'' L.
*'' Artemisia japonica'' Thunb. – ''otoko yomogi''
*'' Artemisia laciniata'' Willd. – Siberian wormwood
*'' Artemisia lactiflora'' Wall. ex DC. – white mugwort
*'' Artemisia longifolia'' Nutt. – longleaf sagebrush, longleaf wormwood
*'' Artemisia ludoviciana'' Nutt. – gray sagewort, prairie sage, white sagebrush, Louisiana-sage, western-sage
*'' Artemisia maritima'' L. – sea wormwood, ''absinthe de mer''
*'' Artemisia marschalliana'' Spreng.
*'' Artemisia michauxiana'' Bess. – Michaux sagebrush, Michaux's wormwood, lemon sagewort
*'' Artemisia nesiotica'' Raven – island sagebrush
*'' Artemisia norvegica'' Fr. – Norwegian mugwort, alpine sagewort
*'' Artemisia nova'' A.Nels. – black sagebrush, small sagebrush
*'' Artemisia olchonensis'' Leonova
*'' Artemisia orientalixizangensis'' Y.R.Ling & Humphries
*'' Artemisia packardiae'' J.Grimes & Ertter – Packard's wormwood, Succor Creek sagebrush
*'' Artemisia pallens'' Wall
*'' Artemisia palmeri'' A.Gray – San Diego sagewort
*'' Artemisia papposa'' S.F.Blake & Cronq. – Owyhee sage, Owyhee sagebrush
*'' Artemisia pedatifida'' Nutt. – birdfoot sagebrush, matted sagewort
*'' Artemisia pontica'' L. – Roman wormwood, green-ginger
*'' Artemisia porteri'' Cronq. – Porter's wormwood, Porter mugwort
*'' Artemisia princeps'' Pamp. – Japanese mugwort, ''yomogi''
*'' Artemisia pycnocephala'' (Less.) DC. – beach wormwood, coastal sagewort
*'' Artemisia pygmaea'' A.Gray – pygmy sagebrush
*'' Artemisia rigida'' (Nutt.) A.Gray – scabland sagebrush
*'' Artemisia rothrockii'' A.Gray – timberline sagebrush
*'' Artemisia rupestris'' L. – rock wormwood
*'' Artemisia schmidtiana'' Maxim. – angel's hair
*'' Artemisia scoparia'' Waldst. & Kit. – redstem wormwood, yin-chen wormwood
*'' Artemisia senjavinensis'' Bess. – arctic wormwood
*'' Artemisia serrata'' Nutt. – sawtooth wormwood
*'' Artemisia sieversiana'' Willd. – sieversian wormwood
*'' Artemisia spiciformis'' K.Koch
*'' Artemisia spinescens'' D.C.Eaton – budsage yn. ''Picrothamnus desertorum''*'' Artemisia stelleriana'' Bess. – hoary mugwort, oldwoman, Dusty Miller, beach wormwood
*'' Artemisia suksdorfii'' Piper – coastal wormwood, Suksdorf sagewort
*'' Artemisia thuscula'' Cav.
*'' Artemisia tilesii'' Ledeb. – Tilesius' wormwood, Aleutian mugwort
*'' Artemisia tridentata'' Nutt. – big sagebrush, blue sage, black sage, basin sagebrush, common sagebrush
*'' Artemisia tripartita'' Rydb. – threetip sagebrush
*'' Artemisia umbelliformis'' Lam. – Alps wormwood, alpine wormwood
*'' Artemisia verlotiorum'' Lamotte – Chinese wormwood
*'' Artemisia viridis'' Willd. ex DC.
*'' Artemisia vulgaris'' L. – mugwort, felonherb, green-ginger, common wormwood

Formerly placed here

*'' Centipeda minima'' (L.) A.Braun & Asch. (as ''A. minima'' L.)
*'' Eupatorium capillifolium'' (Lam.) Small (as ''A. capillifolia'' Lam.)
*'' Filifolium sibiricum'' (L.) Kitam. (as ''A. sibirica'' (L.) Maxim.)
*'' Grangea maderaspatana'' (L.) Poir. (as ''A. maderaspatana'' L.)
*'' Matricaria discoidea'' DC. (as ''A. matricarioides'' auct.)

Ecology

''Artemisia'' species are found on every continent except Antarctica, and have become part of many ecosystems around the world as a result. Below is currently a partial view of the importance of ''Artemisia'' species in ecosystems around the world.

North America

In North America, several species of ''Artemisia'' have become important parts of local environments, with wide adaptability. ''Artemisia papposa'' described by S.F.Blake & Arthur Cronquist can grow in the harsh, dry expanses of alkali flats, but also adapts to meadowlands.

Sagebrushes like ''A. papposa'' (of the ''Tridenteae'' subgenus) in general are found in the north and southwest areas of the North American continent. In the Intermountain West, in a habitat known as Sagebrush Steppe, ''A. tridentata'', ''A. tripartite'', and ''A. arbuscula'' grow alongside various grasses and species of bitter bush, creating an important environment for mule deer, pygmy rabbits, antelopes, and the sage grouse. Understanding the phylogenetic relationships among the sagebrushes has been helpful in understanding the relationships among these plants and their environments, as well as learning more about how these plants formed these communities over long stretches of time. Sagebrushes, which include ''A.'' ''ludoviciana'' and ''A. Tridentata'' among others, can often also be found growing near junipers, particularly in the Elkhorn Mountain region, where the Juniper Woodlands form an ecosystem which provide cover for many animal species in both summer and winter months and storms. Because the habitat should burn only every 400–600 years, with sagebrush shrubs living as long as 200 years (though potentially typically 88), this particular combination of ''Artemisia'' with other flora form an enduring habitat. As it often goes, however, governments and farming businesses have often cleared sagebrush-juniper communities to create land for cow and domestic animal feedcrops, and Artemisia species may be declining due to this and invasive species such as cheatgrass. Destabilization of the vegetation creates higher risk of fires, causing concern among the local conservation and wildlife groups.

Due to their often extensive rhizome systems and other potential characteristics, however, some Artemisia species are often resilient to mowing or pulling, giving some species of Artemisia the ability to easily become invasive if introduced to comfortable, though non-native habitats.
*''A. annua'' (native to Eurasia) is found in wetland habitats, and though it has been naturalized in much of North America it is considered weedy or invasive by some localities, such as Kentucky.
*This is particularly true of ''Artemisia vulgaris'', known as "common mugwort", in North America, where it was introduced by European colonists and settlers in the 1600s, when Jesuit priests and other colonizers may have first brought the herb for ointments and teas and likely also let into port cities via ballast dumping. A''rtemisia vulgaris'' will grow in dense groups and out-compete other plants in an area, in part due to its ability to grow on poorly enriched soils. Disturbed habitats, cities and roadsides or parking lots can easily become a field of ''A. vulgaris'', which is the Artemisia species designated as invasive by New York State.

Cultivation and uses

The aromatic leaves of some species are used for flavouring. Most species have an extremely bitter taste. '' A. dracunculus'' (tarragon) is widely used as a culinary herb, particularly important in French cuisine.

'' Artemisia vulgaris'' (mugwort) was used to repel midges (Old English ''mucgwyrt'' seems to be derived from ''mycg'' ), fleas and moths, intestinal worms, and in brewing (mugwort beer, mugwort wine) as a remedy against hangovers and nightmares.

'' Artemisia absinthium'' is used to make the highly potent spirit absinthe. Malört also contains wormwood. The aperitif vermouth is a wine flavored with aromatic herbs, but originally with wormwood.

'' Artemisia arborescens'' (tree wormwood, or ''sheeba'' in Arabic) is an aromatic herb indigenous to the Middle East used in tea, usually with mint.

A few species are grown as ornamental plants, the fine-textured ones used for clipped bordering. All grow best in free-draining sandy soil, unfertilized, and in full sun.

The largest collection of living Artemisia species, subspecies and cultivars is held in the National Collection of Artemisia in Sidmouth, Devon, UK, which holds about 400 taxa. The National Collection scheme is administered by Plant Heritage (formerly National Council for Conservation of Plants and Gardens, NCCPG) in the British Isles.

Medicinal uses

Artemisinin (from '' Artemisia annua'') and derivatives are a group of compounds used to treat malaria. Treatments containing an artemisinin derivative ( artemisinin-combination therapies) are now standard treatment worldwide for malaria caused by ''Plasmodium falciparum''. Administering ''Artemisia annua'' as dried whole leaves may cause resistance to develop more slowly than if it is administered as pure artemisinin.

Tu Youyou received the 2015 Nobel Prize in Physiology or Medicine for her discovery of the semisynthetic derivatives. She conducted research on traditional Chinese medicine and potential contributions to cures for malaria, on the basis of folk medicine and ancient Chinese texts. From reviewing ancient Chinese texts, they found that the compound artemisinin was optimally extracted at lower temperatures, as high temperature water poured over sweet wormwood leaves destroyed essential treatment properties.

The World Health Organization does not support the promotion or use of ''Artemisia'' plant material in any form for the prevention or treatment of malaria. They note that the plant form of medication has several problems. These include a lack of consistent artemisinin content, the content being low enough that recurrence of malaria often occurs, that the use of the plant may contribute to widespread artemisinin resistance, and that the plant form is not effective in malaria prevention.

References

Further reading

*

External links

Flora Europaea: ''Artemisia''
*Chinese Plant Names
''Artemisia'' species list
an
''Seriphidium'' species list
*Flora of Pakistan
''Artemisia''
an
''Seriphidium'' species list

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Medicinal plants
Asteraceae genera