Asteraceae

The Asteraceae (Asteraceae), also called Compositae (Compositae Giseke, nom. cons.), have 32,913 species divided into some 1,911 genera, making them the Angiosperm family with the greatest richness and biological diversity. The family is characterized by presenting the flowers arranged in a compound inflorescence called capitulum which is surrounded by one or more rows of bracts (involucre).

The name "Asteraceae" It derives from the type genus of the family Aster, a term that —in turn— comes from the Greek ἀστήρ, which means “star” and alludes to the shape of the inflorescence. On the other hand, the name "compounds", older, but valid, refers to the particular type of compound inflorescence that characterizes the family and which is only found in very few families of Angiosperms.

Compositae are of considerable ecological and economic importance. Members of this family range from the polar regions to the tropics, conquering all available habitats, from dry deserts to swamps, and from jungles to mountain peaks. In many regions of the world, Compositae make up up to 10% of the vernacular flora. The family contains some genera with a large number of species, such as Eupatorium s.l. (1200 species), Senecio (with 1000 species) and Helichrysum (500-600 species).

Description

Habit

Most Compositae species are herbaceous plants, rarely trees, shrubs, or lianas. Many species present latex and also essential oils. They may or may not be resinous. The leaves, in general, are well developed, in some cases they are very reduced. In general they are not succulent plants, although there are some examples of compositae with that characteristic. They may be annual, biennial, or perennial, with or without a basal aggregation of leaves (a basal 'rosette'). There are hydrophytic species (certain species of Bidens or Cotula), which have submerged and emergent leaves. On the other hand, there are heliophytic, mesophytic and xerophytic species.

Leaves

Composite leaves are usually alternate and whorled, less frequently opposite, rarely whorled. Regarding its consistency, the leaves can be herbaceous, fleshy, leathery or membranous and be more or less modified into thorns. They can be stalked or sessile, with or without glands, aromatic, fetid or without a marked odor. Regarding the morphology, the leaves can be simple or compound, occasionally peltate. The leaf blade can be entire or dissected, pinnatifid or palmatifid, sometimes spiny. They generally lack stipules. Leaf-blade margins may be entire, crenate, serrate, or dentate; flat, revolute or involute. The leaves do not have a persistent basal meristem. In most Compositae the leaf veins comprise a median vein and more or less similar lateral veins. Such leaves are described as "pinnately venated". Venation in other Compositae frequently consists of a midvein and pronounced lateral veins. Such leaves are described as 3-veined, 5-veined, etc. depending on the number of lateral veins present.

Anatomy

Compositae, mainly members of the Cichorieae, can present specialized structures to secrete latex called laticifers. These laticifers can be found in one or several organs of the plant. Occasionally they can present foliar structures for the elimination of liquid water called hydathodes. The leaf blades may present secretory cavities, with resins or with latex.

The minor veins of the leaf may contain specialized cells for the transport of photoassimilates from the mesophyll to the sieve element of the phloem, called transfer cells. Such a cell type was detected in 58 genera of Compositae. Certain genera do not, such as Eupatorium and Barnadesia.

Regarding the anatomy of the stem, the nodes can be uni, tri or multilacunate. Secondary stem thickening may not occur or may develop from a conventional cambial ring. Sometimes this secondary growth is abnormal, in the sense that it occurs from concentric cambial rings.

Compositae often have sessile or subsessile glandular hairs, consisting of multicellular bases supporting globular elements containing resinous or sticky substances. Such structures are called glands, glandular hairs, or glandular trichomes. These glands can be translucent, yellowish to brown, or orange.

Flower

Scheme of a thin flower: A = inferous ovary; B = vilane; C = anteres of the welded stamens in tube with the free filaments soldiers to the corolla; D = limp; E = style surrounded by the staminal tube and with its outstanding bifid stigma.

Scheme of a tubulous flower (flox): A = inferous ovary; B = merged tube of the corolla with 4 or 5 lobes; C = anteres of the welded stamens in tube; D = style surrounded by the staminal tube and its outstanding bifid stigma.

Chapter Helianthus (Asteraceae) showing the disposition of tubulous and ligulated flowers on the common receptacle.

The flowers are small, hermaphroditic, or sometimes functionally unisexual or sterile (in the latter case they are called neutral). Due to their symmetry, they can be both actinomorphic and zygomorphic, that is, they can present radial or bilateral symmetry, respectively. Due to the number of parts that make up each cycle, the flowers of the composite flowers are pentamerous. Absent hypanthus.

The calyx is null or the sepals are deeply modified, forming a papus or papus, with two to many scales, bristles or hairs, persistent, sometimes connate. The papus may be hairy, minutely bearded, or feathery.

The corolla is gamopetal, the five petals can join together to form a tube with 4 or 5 lobes (the flower is called tubulose or floret), or two groups of united petals (in the case of the bilabiate flowers, with an upper lip formed by 2 petals and a lower lip formed by 3 petals), or they can present a short tube and the blade extended laterally in a ligule with 3 or 5 teeth (ray florets).

The androecium usually has 5 stamens, which alternate with the lobes of the corolla. The filaments, almost always free, are inserted laterally in the corolla tube and the anthers, basifix and with longitudinal and introrse dehiscence, are usually welded together (rarely the filaments are connate and the anthers are free: for example in the Ambrosiinae of the tribe Heliantheae), thus forming a tube around the style in which the pollen, usually tricolporated (with 3 openings), is released, and the style then grows through this tube, pushing out or taking in the pollen (with variably developed hairs) and presented to floral visitors, after which the stigmas become receptive (i.e., with a plunger or brush pollination mechanism).

The gynoecium has 2 connate carpels, inferior ovary, unilocular. They present a single anatropous ovule, with 1 integument and a thin megasporangium. The placentation is basal. The pistil presents a style that usually has a nectary at its apex. The style is divided distally into two branches (stylar branches) that present stigmatic papillae on their adaxial face arranged in two separate lines or in a single continuous band.

Inflorescence

Scheme of an inflorescence in chapter.

The capitulum is a type of racemose or open inflorescence in which the peduncle widens at the extremity forming a somewhat thick disk, called the common receptacle or clinanto, which It can be flat, concave, convex or conical. This common receptacle is surrounded by one or more series of bracts, commonly referred to as involucre bracts and which constituted the involucre. On this organ the sessile flowers are arranged, accompanied or not by their corresponding bracts (generally described as bracts, hairs or axilant scales and which in fact are similar to the bracteoles of, for example, the umbelliferae). It is the typical inflorescence of the Compositae and some other genera such as Scabiosa.

The capitula may have only tubular flowers, may have tubular flowers in the center and bilabiate outward, the latter female or sterile and the former male or bisexual, or they may have only ray florets, with valvate corolla lobes. If they have only tubular flowers, these may be all bisexual, or they may be a mixture of sterile female flowers with staminate bisexuals, in the same or different flower heads.

The capitula, in turn, can be grouped into diverse, determined, terminal or axillary compound inflorescences.

Fruit

Detail of a cistern. Note the papus or vilano that will allow the spread of the fruit with the wind.

Usually, the fruit of Compositae is described as an achene because of its resemblance to true achenes. However, by definition, achenes are dry, unseminated fruits, derived from unicapellar and superior ovaries. The ovaries of the compound, on the other hand, are bicarpellate and inferior. For that reason Compositae fruits are correctly described as cipselas, a term coined by C. de Mirbel in 1815. The morphology of a Compositae ovary during flowering is markedly different from that of the fruit. mature that derives from such an ovary. The shapes of cypselas have been used by taxonomists to distinguish species, genera, and even subtribes. In most species of the family the cypselae are more or less isodiametric in cross section, while in some species it is lenticular to elliptical. Such fruits are said to be compressed if the major axis of the cross section is more or less parallel to a radius of the chapter (as for example in Verbesina) or radially flattened. if the minor axis of the cross section of the fruit is parallel to a radius of the capitulum (as in the case of Coreopsis).

As previously mentioned, the calyx in the Compositae is modified and, moreover, it is persistent in the fruit (it is said to be acrescent) and is called papus or papus. This organ shows great morphological diversity (edges, hairs, crowns, bracts, etc.) and is frequently used as a diagnostic character for the recognition of genera and species of composites. In some taxa an elongated spike is formed between the fruit and the papus. The seed is exalbuminate and the endosperm is scarce or non-existent.

Phytochemistry

Composites store carbohydrates as oligosaccharides, including inulin. Polyacetylenes and terpenoid aromatic oils are usually present in species of the family. Sesquiterpene lactones are frequently present (however, without iridoids).

Chromosome numbers

The species of the family have basic chromosome numbers from x=2 to x=19. The basic number of the family is assumed to be x=9. Brachicome lineariloba is a short-lived mayfly native to Australia which, with only 4 chromosomes 6–8 µm in length in its somatic cells, is the compound with the lowest known chromosome number.

Playback modes

Tubulous flowers, hermaphrodites, freeing the pollen in a Composition.

The pollen grains of the compounds are spiny to facilitate their adherence to the insects that carry out pollination. In the image are shown the grains of sunflower pollen (Helianthus annuus).

The diversity of modes of reproduction of Compositae is only paralleled by their morphological heterogeneity. There are dioecious species (that is, with female plants and male plants, such as Baccharis articulata) and others in which unisexual individuals coexist with hermaphrodites in the same population (Bidens sandvicensis, for example). However, most of the composites are hermaphrodites, that is to say that both sexes occur in the same flower. These hermaphrodite species, in turn, can be autogamous or allogamous, depending on whether or not they can produce seeds by self-fertilization, respectively. In the case of allogamous composites, it has been determined that self-pollination is prevented due to a particular self-incompatibility mechanism called homomorphic sporophytic self-incompatibility. Its peculiarities are that the incompatibility reaction between pollen and pistil is governed by the genotype of the plant that gives rise to the pollen grains (that is, by the sporophyte) and not by the genotype of each pollen grain. individual. In this self-incompatibility system, determined by a single gene called S, pollen tube growth arrest occurs in the stigma, as soon as germination begins. A fairly distributed mode of reproduction in this family is apomixis. Apomixis is defined as asexual reproduction through seeds. In this reproductive system, embryos develop by mitosis from an unreduced oosphere without fertilization taking place. In other words, each embryo produced is genetically identical to the mother plant. Apomixis is widely distributed in certain families of plants, such as Poaceae, Rosaceae, and Compositae. In the latter, apomixis is a type of obligate reproduction in many species, while in the other two families apomixis and sexual reproduction can take place, side by side, in the same individual (facultative apomixis). Apomictic reproduction has been detected in several genera of Compositae, such as Achillea, Crepis, Hieracium, Taraxacum, Conyza, Eupatorium, Erigeron, Brachycome, Parthenium, and Arnica.

Many of the apomictic species of the composites are sterile due to autopolyploidy (the triploid species Taraxacum officinale and Erigeron annuus, for example) and interspecific hybridization (such is the case of Arnica gracilis, a hybrid species between A. latifolia and A. cordifolia). Interspecific hybrids often present chromosome segregation problems during meiosis due to improper chromosome pairing. Because of this they are highly sterile. The selective advantage of apomictic reproduction becomes evident considering that in these otherwise sterile individuals, their reproduction and dispersal by means of seeds is ensured. From an ecological point of view, apomictic species are frequently distributed in disturbed habitats and are very successful colonizers, since they do not depend on the presence of individuals of the same species in the immediate vicinity to leave offspring.

The genetics of apomixis in Compositae has been investigated at least for the triploid species Erigeron annuus, and is determined by two independently segregating genes.

Ecology

The family is cosmopolitan, its species inhabit from cold zones to the tropics, passing through temperate and subtropical zones. They are especially frequent in number of species or number of individuals in open arid or semi-arid regions and montaneous regions, in subtropical or temperate latitudes.

The small flowers of Asteraceae are not easy to see, the flower heads usually function as (and at first glance may even appear to be) a single flower. In flower heads with tubulose flowers in the center and bilabiate outwards, the bilabiate flowers are the ones that attract pollinators and the tubulose ones mature centripetally. Pollinators usually land on the bilabiate flowers and deposit pollen from other plants on the stigmas of the older, marginal tubular flowers. The filaments of many Asteraceae respond to touch by contracting abruptly, forcing pollen out onto the pollinator's body. The color of the corolla is variable. Compositae inflorescences often interbreed and attract a wide variety of generalist pollinators (such as butterflies, bees, flies, and beetles), but pollination by solitary bees is especially common. Some genera have reduced flowers that are pollinated by wind (anemophily, such as Ambrosia and Baccharis), and some have flower heads reduced to a single flower, but these reduced flower heads are later aggregates into compound heads (as in Echinops).

Fruits of most members of the Asteraceae are dispersed by wind, with the papus functioning as a parachute. The flattened and often winged fruit helps dispersal by wind. External transport on birds or mammals is facilitated by modifications of the papus such as bristles with retroverse wattles, hook- or spine-like fruit growths, or specialized involucral bracts.

Evolution, phylogeny and taxonomy

Evolution

Basal asterids and campanulids apparently originated in the early Cretaceous period, and asterals in the late Cretaceous. A late Cretaceous origin has been hypothesized for Asterales in eastern Gondwana (Australasia) with a later expansion into western Gondwana (South America and Antarctica), where the Asteraceae would have originated before the separation of the Americas and Antarctica.

On the other hand, it has been argued that the close relationship between the Asteraceae with the Goodeniaceae and Calyceraceae families, in addition to the basal position of the Barnadesioideae compound subfamily, indicate that the complex originated in South America, Antarctica and Australia. Fossil pollen data suggest an Eocene South American origin of Asteraceae, with a later migration to North America in the late Eocene or Oligocene. However, pollen from Asteraceae (assignable to Mutisioideae) has recently been reported. from the Paleocene-Eocene of South Africa, which would indicate an earlier origin of the family in eastern Gondwana.

Phylogeny

Diversity of chapters in compounds. 1.- Anthemis tinctoria (Asteroidae), 2. Glebionis coronarium (Asteroidae), 3. Coleostephus myconis (Asteroidae), 4.- Glebionis sp. (Asteroidae), 5. Sonchus oleraceus (Cichoireideae), 6. Cichorium intybus (Cichoireideae), 7.- Gazania governs (Cichoireideae), 8.- Tithonia rotundifolia (Asteroidae), 9.- Calendula arvensis (Asteroidae), 10. Leucanthemum vulgare (Asteroidae), 11. Hieracium lachenalli (Cichoireideae), 12.- Osteospermum ecklonis (Asteroidae).

Asteraceae have been the focus of numerous phylogenetic analyses.

Asteraceae form a fairly obvious and easily recognizable monophyletic group. Both morphological and molecular synapomorphies are numerous.

The family is divided into numerous tribes that, until recently, were arranged into 3 subfamilies (K.Bremer 1987, 1994, Bremer and Jansen 1992).

The Barnadesioideae, a small South American group comprised mainly of trees and shrubs, are sister to the rest of the family (Jansen and Palmer 1987). This group lacks the inversion of chloroplast DNA that characterizes the rest of the species in the family (Jensen and Palmer 1987). The rest of the tribes are divided more or less equally between the "Cichorioideae" and the "Asteroideae" (K. Bremer 1987, 1994, Carlquist 1976, Thorne 1992). "Cichorioideae" it is paraphyletic, but the phylogenetic relationships within the complex are not yet fully understood. "Cichorioideae" it is characterized by branches of the style with the stigmatic inner surface. Their heads are usually discoid, except in the tribe Lactuceae, which have ray heads. Both resin and laticiferous canals are found in this subfamily, and the latex system is especially well developed in Lactuceae. Lactuceae is quite different from the rest and has sometimes been placed in its own subfamily (Cronquist 1955, 1977, 1981), but it is closely related to Vernonieae. The monophyletic Asteroideae can be diagnosed by having stigmatic tissue restricted to 2 lines on each branch of the style, lack of laticifers, presence of bilabiate flowers (and bilabiate flower heads, though lost in some genera), lobed tubular flowers. short (but secondarily elongated in some), and DNA characters.

The family has recently been classified into at least 11 subfamilies (Panero and Funk 2002). A further subfamily was added later: Wunderlichioideae, with 8 genera and 24 species in South America and China.

Taxonomy

The Asteraceae have long been recognized as a natural group and their circumscription has never been controversial (although some taxonomists have subdivided the family into 2-3 families). Arthur Cronquist arranged the Asteraceae as the only family in the order Asterales within the subclass Asteriidae, associated with the orders Gentianales, Rubiales, Dipsacales, and Calycerales and relatively distant from Campanulales. Molecular systematics methods used by the Angiosperm Phylogeny Group (APG) have made it possible to better understand the phylogenetic relationships between plant groups. In its 2003 publication, the APG suggested that the Asteraceae are part of a more broadly defined order Asterales, within the informal clade Asteridas II (or, Campanulid clade, see Judd and Olmstead, 2004).

As currently defined, the order Asterales includes the following families with valvate petals, which store inulin, and which contain ellagic acid: Alseuosmiaceae, Argophyllaceae, Calyceraceae, Campanulaceae (optionally including Lobeliaceae), Goodeniaceae, Menyanthaceae, Pentaphragmataceae, Phellinaceae, Rousseaceae and Stylidiaceae.

The family most closely related to Compositae is Calyceraceae, distributed in South America, with which it shares the presence of a highly modified and accrescent calyx, unicarpelar and uniseminate gynoecium, pollen with furrows between the colpi, and specialized fruit. The aggregation of the flowers in flower heads was apparently a phenomenon of parallel evolution in both families, since it is a determinate inflorescence in Calyceraceae while it is indeterminate in Asteraeae.

Composite synapomorphies include: calyx modified into a structure called papus, connate anthers forming a tube and stigmas modified to function as brushes in a specialized pollination mechanism, ovaries containing a single basal placentation ovule and the production of sequiterpene lactones.

The family, then, has been universally recognized and arranged in the order Asterales of the dicots or eudicots. From the point of view of intrafamilial taxonomy, two subfamilies have traditionally been recognized: Asteroideae (or 'Tubuliflorae') and Cichorioideae (or 'Liguliflorae'), since in 1894 Hoffmann recognized the same as two different lineages. Asteroideae is characterized by the presence of radiate capitula and the absence of latex. The Cichorioideae subfamily, on the other hand, is characterized by the presence of latex and by its flower heads with ray florets.

Attempts to sort Compositae diversity into lower taxonomic categories, such as tribes, began with H. Cassini, who in 1826 subdivided the family into 19 tribes and suggested their natural relationships, and were continued by contributions from G. Bentham in 1873 and Arthur Cronquist in 1955. The phylogenetic study carried out by R.K. Jensen and J.D. Palmer on chloroplast DNA and published in 1987 was central to establishing that, in addition to Cichoroideae and Asteroideae, there was another clade (later named Barnadesioideae) distributed throughout South America and that it was basal within the family. The morphological data added to the cladistic analyzes allowed K. Bremer to suggest a classification of the Composites that included three subfamilies and 17 tribes, the synopsis of which is provided later.

The phylogenetic studies carried out over the last two decades on DNA sequences have led to the conclusion that the Cichorioideae are paraphyletic. More recently, the molecular studies of J.L. Panero and V.A. Funk recognize 12 subfamilies, each monophyletic, which are briefly described below.

Subfamilies and tribes

Chuquiraga oppositifolia.

1. Barnadesioideae (D. Don) Bremer & jansen

Usually arboreal, notably poor in flavonoid compounds. In addition, axillary thorns or stingers are very common. The flowers and cypselas have long tricellular hairs. The corolla is bilabiate (4+1), the pollen is not spiny and has depressions between the colps, the style is glabrous or with papillae, the stigma is lobed. The cypsela presents thorns. It comprises 9 genera and 94 species that are distributed in South America, especially in the Andes. The age of the "stem" of this clade is between 42 and 36 million years before present (K. J. Kim et al. 2005). Some of the genera of this subfamily, which includes a single tribe (Barnadesieae), are: Arnaldoa, Barnadesia, Chuquiraga, Dasyphyllum , Doniophyton, Fulcadea and Schlechtendalia.

Trixis californica.

2. Mutisioideae Lindley (synonyms: Mutisiaceae Burnett, Nassauviaceae Burmeister, Perdiciaceae Link)

This subfamily presents flowers with bilabiate corollas, but, unlike Barnadesioideae, the petals form two groups, one made up of three members and the other two. The stigma lobes are short. The basic chromosome number is n=6 to 9.

The subfamily has 44 genera and approximately 630 species that are distributed in South America. The 44 genera are grouped into the following tribes: Onoserideae (Onoseris, Lycoseris), Nassauvieae (Nassauvia, Criscia), Mutisieae (example Gerbera, Mutisia) The genera with the largest number of species are Acourtia (65), Chaptalia (60), Mutisia (50) and Trixis (50).

3. Stifftioideae Panero

It is a recently proposed subfamily. It includes about 10 genera and 40 species distributed mainly in Venezuela and Guyana, although it also has representatives in the Andes and northeastern South America. Some of the genera that make up this subfamily, which includes a single tribe called the Stifftieae, they are Hyaloseris, Dinoseris, Duidaeae, Gongylolepis and Stifftia.

4. Wunderlichioideae Panero & funky

Subfamily that includes 8 genera and approximately 24 species that are distributed especially in Venezuela and Guyana, although it also has species in eastern South America and southwest China. The most outstanding characteristic of the members of this subfamily is to present glabrous styles and stylar branches and a deletion in the rpoB gene. Two tribes are recognized in this subfamily: Wundelichieae and Hyalideae.

5. Gochnatioideae Panero & funky

With 4 or 5 genera and about 90 species that are distributed throughout South America and Central America, especially the Caribbean. This subfamily, which includes a single tribe called Gochnatieae, is characterized by its flowers with short, glabrous stylar branches and rounded apices. The basic chromosome numbers are n = 22, 23 and 27. The most represented genus is Gochnatia which includes about 70 species. The other genera in the subfamily are Richterago, Cnicothamnus and Cyclolepis.

6. Hecastocleidoideae Panero & funky

Subfamily characterized by its uniflorous flower heads, polysymmetrical flowers with five-lobed corollas, short stylar arms with rounded apex, and scaly papus. This subfamily, whose basic chromosome number is x=8, comprises a single tribe (Hecastocleideae) and a single species: Hecastocleis shockleyi distributed in the southwestern United States.

Inflorescence of Carduus acanthoides, note the involution of spiny bracts surrounding the chapter.

7. Carduoideae Sweet (syn.: Acarnaceae Link, Carduaceae Dumortier, Centaureaceae Martynov, Cynaraceae Durande, Echinopaceae Dumortier, Serrulataceae Martynov)

It is a subfamily that comprises a hundred genera and some 2850 species of cosmopolitan distribution, but with a marked concentration of species in the Northern Hemisphere (Eurasia and North Africa). The biennial habit is very common. They have dissected, laticiferous leaves and the flowers are usually zygomorphic. The stylar rami are short, with a ring of hairs below the stylar rami. The basic chromosome number is n=12.

The genera of this subfamily are divided into 4 tribes: Cynareae (=Cardueae), Dicomeae, Oldenburgieae and Tarchonantheae. The generic taxa with the largest number of species are Centaurea (695), Cousinia (655), Saussurea (300), Cirsium (250), Echinops (120), Carduus (90), Serratula (70), Dicoma (65), Onopordum (60).

Inflorescence of Pertya scandens.

8. Pertyoideae Panero & funky

Subfamily comprising 5 or 6 genera and about 70 species included in a single tribe (Pertyeae) and distributed in Asia (Afghanistan towards the southeast of the continent). The flowers have a deep and unequally divided corolla, the stigmatic arms are short, hairy to papillose on their abaxial face. The basic chromosome number is x=12 to 15. The largest genus is Ainsliaea with approximately 50 species.

9. Gymnarrhenoideae Panero & funky

This is another monotypic subfamily, made up of a single tribe (Gymnarrheneae) that includes a single species, Gymnarrhena micrantha distributed in North Africa. The chapters are grouped in inflorescences. The stylar branches are long and with rounded apices. The basic chromosome number is x=10.

Inflorescence of Cichorium intybusNote that all the flowers are ligulated and that they have 5 teeth in their apical portion.

10. Cichorioideae Chevalier (syn.: Aposeridaceae Rafinesque, Arctotidaceae Bessey, Cichoriaceae Jussieu, nom. cons., Cnicaceae Vest, Lactucaceae Drude, Picridaceae Martynov, Vernoniaceae Burmeister)

It is a subfamily with a significant number of genera (224) and species (3600) with a cosmopolitan distribution. They present latex, the disk flowers are deeply lobed, the apices of the stylar arms are acute, and the hairs are also acute. The most frequent basic chromosome numbers are 9 or 10, more rarely 7 or 13. The genera with the highest species richness are: Vernonia (800-1000), Crepis (200), Jurinea (200), Scorzonera (175), Lepidaploa (115), Tragopogon (110), Lessinganthus (100), Hieracium (90-1000), Lactuca (75), Vernonanthura (65), Hypochaeris (60), Sonchus (60) and Taraxacum (60-500). This subfamily has been subdivided into the following tribes: Gundelieae, Cichorieae, Arctotideae, Liabeae and Vernonieae.

11. Corymbioideae Panero & funky

This subfamily with a single tribe (Corymbieae) comprises a single genus (Corymbium) with 7 species native to South Africa. It presents leaves with parallel veins, flower heads enclosed by two involucral bracts. The corolla with broad and conspicuous lobes. The basic chromosome number is x= 16.

Chapter heterogam in Aster, note the central tubulous flowers, still closed and yellow, and the ligulated flowers of red colour, on the margins of inflorescence.

12. Asteroideae Lindley

With 1,135 genera and more than 16,000 species, this is the richest subfamily of the Compositae. Its members, of cosmopolitan distribution, do not present latex, the flower heads are heterogamous, with tubular flowers with inconspicuous lobes and ray florets frequently with three lobes. The stigmatic areas are arranged in two marginal rows. The genera with the highest species richness are Senecio (1000), Eupatorium sensu lato (1200, 40 in the strict sense), Helichrysum (600), Artemisia(550), Mikania (430), Baccharis (400), Verbesin i> (300), Ageratin (290), Bidens (235), Stevia (235), Anthemis (210), Erigeron (200), Pentacalia (200), Aster (180), Viguiera (180), Chromolaena (165), Gnaphalium (150), Solidago (150), Tanacetum (150), Olearia (130), Seriphidium (130), Ligularia (125), Achillea (115), Coreopsis (115), Anaphalis (110), Brickellia (110), Calea (110), Blumea (100), Koanophyllum (110), Euryops (100), Pectis (100) and Wedelia i> (100). 3 supertribes are recognized within this subfamily: Senecionodae, Asterodae, and Helianthodae.

Includes 20 tribes: Anthemideae, Astereae, Athroismeae, Bahieae, Calenduleae, Chaenactideae, Coreopsideae, Eupatorieae, Feddeae, Gnaphalieae, Helenieae, Heliantheae, Inuleae, Madieae, Millerieae, Neurolaeneae, Perityleae, Polymnieae, Tageteae.

Overview of Traditional Classification

The following is a synopsis of the more traditional classification of Compositae based on cladistic analysis of morphological data. Many floras around the world subscribe to this synopsis published by Bremer in 1994, which divides the Compositae into 3 subfamilies, of which the most important in number of species are Cichorioideae and Asteoideae. Note that many of the tribes of Bremer's classification (such as Mutiseae or Cardueae) have been elevated to the rank of subfamilies in the most recent classification.

Barnadesioideae

Barnadesieae Tribe

Cichorioideae

Tribe Arctotideae

Tribu Cardueae

Tribu Cichorieae

Liabeae tribe

Mutisieae tribe

Tribu Vernonieae

Asteroideae

Anthemideae Tribe

Astereae Tribe

Calenduleae Tribe

Eupatorieae tribe

Gnaphalieae Tribe

Helenieae tribe

Tribe Heliantheae

Tribu Inuleae

Plucheae tribe

Tribu Senecioneae

Main genera and species

Due to the large number of genera and species that they include in the world, the list of the genera and the main species of the family has been published in the following annex: Genera and species of Asteraceae.

The most represented genera are Senecio (1000 spp.), Vernonia (1000), Cousinia (650), Eupatorium s.l. (1200), Centaurea (600), Artemisia (550), Hieracium (500-600), Helichrysum (500), Baccharis (400), Mikania (400), Saussurea (300), Verbesin (300), Cirsium (250), Jurinea (250), Bidens (200), Crepis (200), Aster (180, excluding segregates such as Symphyotrichum, Sericocarpus), Gnaphalium (150), Tragopogon (110), and Solidago (100). Generic boundaries are often problematic, and many of these large genera are often divided into numerous segregates (see Bremer 1994).

Synonymy

The following names are considered synonyms of Asteraceae:

Economic importance

The Compositae comprise more than 40 species of economic importance, which include food plants (lettuce, Jerusalem artichoke), oilseeds (sunflower, safflower), medicinal plants (chamomile) and ornamental plants (dahlia, zinnia, chrysanthemum). Also other species of Helianthus, Cichorium, Cynara, Taraxacum, Artemisia containing spices.

High-quality edible sunflower and safflower oils are low in saturated fatty acids and high in unsaturated fatty acids. In addition, other types of oils, such as high oleic acid sunflowers, have been developed by mutagenesis. In addition, many novel fatty acids for the industry are found in the oils of many compounds, such as the conjugated dienolic fatty acids from Dimorphoteca, the acetylenic fatty acids from Crepis and the epoxy fatty acids in Vernonia and Stokesia.

The various species of the family are a rich source of insecticides and other chemical substances for industrial use, such as pyrethrum (Tanacetum, or in Crisanthemum), Pulicaria, the gum (in guayule).

Many other Compositae are cultivated as medicinal plants or as aromatic herbs.

Ambrosia is the major cause of hay fever.

They are found ornamental on Calendula, Dendranthema, Argyranthemum, Leucanthemum (the chrysanthemum), Dahlia, Tagetes, Senecio, Spaghenticola, Gaillardia, Helianthus, Zinnia, and many others.

Finally, the composites also include a large number of weed species (thistles for example) that cause economic losses to many crops. The following table summarizes several of the uses of the composites and exemplifies each one of them.

Field grown with lettuce (Lactuca sativa), Island of the Meeting.

Garden cultivated with endivia (Cichorium endivia), Botanic Garden of Montreal, Canada.

Cartamus inflorescence (Carthamus tinctorius).

Topinambur tubes (Helianthus tuberosus.)

Asteraceae Glossary

A general and specific glossary of Asteraceae can be found at Glossary of Asteraceae.