Overview

Brief Summary

Introduction

The Asteraceae (Compositae, alternate name) with its approximately 1,620 genera and more than 23,600 species is the largest family of flowering plants (Stevens, 2001). The family is distributed worldwide except for Antarctica but is especially diverse in the tropical and subtropical regions of North America, the Andes, eastern Brazil, southern Africa, the Mediterranean region, central Asia, and southwestern China. The majority of Asteraceae species are herbaceous, yet an important component of the family is constituted by shrubs or even trees occurring primarily in the tropical regions of North and South America, Africa and Madagascar and on isolated islands in the Atlantic and Pacific Oceans. Many species of sunflowers are ruderal and especially abundant in disturbed areas, but a significant number of them, especially in mountainous tropical regions, are narrow endemics. Because of the relentless habitat transformation precipitated by human expansion in montane tropical regions, a number of these species are consequently in danger of extinction.

The family contains several species that are important sources of cooking oils, sweetening agents, and tea infusions. Members of several genera of the family are well-known for their horticultural value and popular in gardens across the world and include zinnias, marigolds, dahlias, and chrysanthemums. The commercial sunflower genus Helianthus has been used as a model in the study of hybridization and its role in speciation (Rieseberg et al., 2003). See list of economically important Asteraceae

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Comprehensive Description

Description

Herbs, suffrutices, shrubs or (rarely) climbers or trees. Leaves alternate, less often opposite. Stipules 0, but false stipules occur in a few species (for example: Vernonia myriantha and Senecio deltoideus) . Flowers small (florets), aggregated into heads (capitula) and simulating single larger flowers and surrounded by a calyx-like involucre of one or more series of bracts (phyllaries). Receptacle of the head expanded, with or without receptacular scales or bristles each subtending a floret. Florets all similar sexually (head homogamous) or central and marginal florets differing (head heterogamous) and then the central florets usually bisexual or rarely male, the outer female or rarely neuter. Calyx never typically herbaceous but represented by a pappus of numerous simple or feathery (plumose) hairs, or a smaller number of membranous scales, teeth or bristles, or by a continuous membranous ring; sometimes 0.

Corolla composed of (3-)5 united petals fused into a tube below and with a distal limb consisting of either:  (1) 5 actinomorphic lobes or teeth (tubular florets); or  (2) a unilateral strap-shaped limb (ray) 0-3(-4)-dentate at the apex; or (3) a unilateral strap-shaped limb (ligule), 5-dentate at the apex.

Stamens 5, borne on the corolla-tube; anthers usually fused into a cylinder around the style. Ovary inferior, 1-celled, with 1 basal ovule; style single below but branching above into 2 stigmatic arms. Fruit an achene, crowned by the pappus, sometimes with a slender beak interposed between them. 
Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© Mark Hyde, Bart Wursten and Petra Ballings

Source: Flora of Zimbabwe

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Fossil Record

The fossil record of Asteraceae is for the most part composed of pollen deposits and fruits. Few pollen records exist for the Eocene but the pollen of Asteraceae becomes increasingly common in samples dated to the Oligocene/Miocene (Graham, 1996). These data show the increasing importance of the family in most biomes of the world from the mid to late Oligocene to present. Pollen samples from Paleocene-Eocene deposits in southwestern Africa have been attributed to Mutisieae (Zavada and De Villiers, 2000; De Villiers and Cadman, 2001) or to a Dicoma-like taxon and recently dated to the mid-Eocene (Scott et al., 2006). Asteraceae pollen dated to the Eocene has also been found in Egypt (Kedves, 1971), China (Song et al., 1999) and North America (Texas Gulf coast, Elsik and Yancey, 2000).

Fossil pollen records have been used recently to shed light on the time of origin of Asteraceae. Dated and properly identified, pollen deposits can be used to place a minimum age for the origin of a particular clade. Using the rate of mutation of the gene rbcL and a fossil calibration, Bremer and Gustafsson (1997) concluded the family to have originated at least 38 Ma. A similar approach using the ndhF and rbcL genes was used by Kim et al. (2005) to date the origin of molecular rearrangements in the chloroplast genome of the Asteraceae. Their study concluded that the family originated in the mid Eocene (42-47 Ma).

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Taxonomy

The initial classification of the family was produced by Cassini (1819a,b) who grouped genera into tribes. His tribal concepts have been refined by taxonomists subsequently and are still the main category above the genus level used to classify sunflowers. The grouping of these tribes into subfamilies is a relatively recent academic pursuit in Asteraceae systematics that began with Carlquist (1976) and Wagenitz (1976) defining the concepts of subfamilies Cichorioideae and Asteroideae. The morphological characteristics used to circumscribe these two groups are mostly based on discontinuities in corolla, anther, and style morphology. According to Bremer (1994), the Asteroideae are characterized (with some exceptions) by having true ray florets, disc corollas with short lobes, caveate pollen, stigmatic surfaces of style branches separated into two marginal lines sometimes confluent at apices, and a distinctive secondary chemistry. These morphological characteristics are rarely seen in Cichorioideae.

With the incorporation of results from molecular phylogenetic studies the classification of the Asteraceae has changed relatively quickly, mainly through the recognition of monophyletic groups traditionally included in Cichorioideae. With the work of Jansen and Palmer (1987), Bremer (1994) recognized three subfamilies (Asteroideae, Barnadesioideae, and Cichorioideae) and 17 tribes. Thorne and Reveal (2007) recognized the same subfamily groups using the possibly earlier name Carduoideae for the Cichorioideae. They expanded the number of tribes to 25, recognizing the three new tribes identified by molecular analysis named in Baldwin et al. (2002) but maintained a polypheletic Heliantheae. Jeffrey (2007) accepted the tribal groupings of Panero and Funk (2002), ultimately recognizing 24 tribes and grouping them into five subfamilies. He recognized a monophyletic Barnadesioideae, a monophyletic Asteroideae, and split the grade of clades between these two groups (Cichorioideae of Bremer (1994) or Carduoideae of Thorne and Reveal (2007)) into 3 subfamilies: Mutisioideae, Carduoideae, and Cichorioideae, each shown to be polyphyletic (Panero and Funk, 2002, 2008). As the capacity to expand both taxon and character sampling in molecular studies has grown, providing more resolution and certainty in phylogenetic analyses, more major lineages of the family have been identified. Increased sampling, particularly sampling of taxa considered anomalous in the family (uncertain tribal position, Bremer, 1994), resulted in the discovery that the genera Corymbium, Gymnarrhena, and Hecastocleis represent monotypic lineages sister to major clades and provided evidence for more lineages than previously recognized. The classification of Panero and Funk (2008), shown in the tree above, recognizes 12 strictly monophyletic subfamilies.

The classification of the Asteraceae is dominated by the large subfamily Asteroideae that contains more than 70% of the species of the family. The three main lineages within Asteroideae found by molecular studies (Kim and Jansen, 1995, Panero and Funk, 2008) have been recognized at the supertribe level recently (Robinson, 2004, 2005) as Asterodae, Helianthodae, and Senecionodae. Other large subfamilies include Carduoideae and Cichorioideae each with more than 2000 species. All other subfamilies each contain less than 1000 species with Gymnarrhenoideae and Hecastocleidoideae containing only one species each.

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Characteristics

The family is characterized by having a capitulum or head, an inferior, unilocular ovary with one ovule, and with few exceptions fused anthers surrounding the style. The capitulum (capitula plural) is a specialized indeterminate inflorescence that can contain 1 to hundreds of individual flowers (florets). The flowering sequence in the capitulum is nearly always from the outside to the center, that is, centripetal (Harris, 1995). The florets sit on the disc or receptacle, an expanded shoot that can be flat, concave, convex, or rarely columnar. The disc and florets are surrounded by bracts or leaf-like structures called phyllaries and collectively forming an involucre. The phyllaries can be arranged in one row and be of equivalent length or can be unequal in length. Most sunflowers have involucres with several series of phyllaries. In these sunflowers the phyllaries can be subequal with all phyllaries of equivalent length or imbricate. Involucres composed of imbricate phyllaries are the most common condition in the family and exemplified by the artichoke (Cynara cardunculus) in which multiple series of phyllaries overlap each other. In some species the outermost phyllaries sometimes resemble leaves. The receptacle can be naked or sometimes have bract-like structures called paleae, scales or hairs surrounding each floret. The involucre can have different shapes ranging from tubular to hemispheric.

Radiate capitulum composed of two types of florets enclosed by the involucre © Jose L. Panero

There are six types of corollas present in the Asteraceae two of which are actinomorphic and the other four are zygomorphic (Bremer, 1994). Actinomorphic corollas are composed of five equivalent lobes and normally termed disc corollas (as they occupy most of the disc area). They have five lobes and when viewed from above, the reflexed lobes of the actinomorphic corolla resemble a five point star. Disc corollas may have fewer lobes with four being the most common departure, although corollas with three lobes are also seen. Tubular corollas are narrow actinomorphic corollas, mostly lacking stamens. Zygomorphic corollas are mostly confined to the first row of florets in the capitulum, although some species may have several rows of zygomorphic corollas. Bilabiate corollas are generally present only in several genera belonging to the earliest divergences of the family. The bilabiate corolla has a 3+2 arrangement of lobes with the 3-lobe lamina facing towards the outside and the 2-lobe lamina to the center of the capitulum. Sometimes the 2 lobes are separate and coiled. The pseudobilabiate corolla has a 4+1 arrangement. The ray floret is present in several tribes of the subfamilies Cichorioideae and Asteroideae and consists of a lamina that terminates in 2-3 lobes. Some members of tribe Arctotideae have a ray floret that terminates in 4 lobes. Ligulate corollas have 5 lobes.

The capitula of sunflowers can contain florets with corollas of the same morphology or a combination of two or sometimes three types of corollas. In discoid capitula all florets have actinomorphic corollas and can be either bisexual and fertile or functionally staminate or pistillate. In radiate capitula the peripheral florets are ray florets and these can be pistillate or styliferous and sterile or neuter (no style present). Radiant capitula are discoid capitula with peripheral corollas having lobes variously expanded. In ligulate or liguliflorous capitula all the florets are bisexual and have ligulate corollas; this capitulum type is only found in members of tribe Cichorieae. Disciform capitula have florets with actinomorphic corollas with peripheral florets having tubular corollas. These peripheral corollas are pistillate. Homogamous capitula have florets exhibiting similar sexual forms whereas heterogamous capitula have florets with two or more sexual forms.

Most sunflower florets have five anthers corresponding to the number of lobes in the corolla. The anthers are positioned along the sinuses of the corolla lobes (alternate to the lobes). The anther filaments are free from the corolla just above the tube and the two thecae (pollen sacs) of each stamen are connate with the thecae of adjacent stamens producing a tube that surrounds the style. Pollen is shed to the interior of this tube (introrse dehiscence). The connective, the tissue connecting the two anther thecae of each anther, may continue beyond the anther thecae and produce an appendage. Some sunflowers do not have appendages (e.g., many Asteroideae: Eupatorieae). The anther collar is located at the end of the filament just below the connective and is an area of sclerified cells involved in the mechanical aspects of pollen presentation in sunflowers. The anther collar is progressively shorter on the adaxial side facing the style. If the thecae extend below the point of insertion between the filament and connective, the anther is calcarate; if not, the anther is ecalcarate. Anthers can have tails, sometimes very elaborate with branched projections. Calcarate and caudate (tailed) anthers are common among the basal lineages of the family whereas ecalcarate anthers are more common in the Asteroideae.

The styles of sunflowers have two stigmatic branches or arms. They may be smooth (glabrous) or pubescent with trichomes confined mostly to the distal end of the style and the abaxial surfaces of the style branches. In fertile florets, the adaxial surface of the style branch has stigmatic (fertile) papillae. In some groups the stigmatic papillae are continuous throughout the style branches, whereas in others the stigmatic papillae are confined to the margins of the style branches. As the floret matures, the style grows through the tube formed by the fused anthers pushing the pollen up. This secondary pollen presentation mechanism ensures pollen is available to insects visiting the capitulum on a daily basis as new florets open. The pollination biology of sunflowers has not been extensively studied but an excellent summary of the available literature is provided by Lane (1996).

Sunflowers produce dry, indehiscent fruits termed cypselae (achenes in many publications). A few species have fleshy fruits reminiscent of a drupe (Chrysanthemoides, Tilesia). Most species have a pappus on the distal end of the cypsela. This structure is derived from the calyx of the floret (Carlquist, 1976). The pappus aids in dispersal or defense against herbivory (Stuessy and Garver, 1996).


Fruits of Hyalis argentea. © Jose L. Panero

For additional general information concerning the morphology of sunflowers the reader is advised to consult the introductory chapter for the family in Flora North America (Barkley et al., 2006).

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Ecology

Associations

Foodplant / feeds on
Aeolothrips intermedius feeds on flower of Asteraceae
Other: major host/prey

Foodplant / feeds on
adult of Aeolothrips tenuicornis feeds on live flower of Asteraceae

In Great Britain and/or Ireland:
Foodplant / nest
female of Andrena denticulata provisions nest with pollen of Asteraceae

Foodplant / nest
female of Andrena fulvago provisions nest with pollen of Asteraceae

Foodplant / nest
female of Andrena humilis provisions nest with pollen of Asteraceae

Foodplant / nest
female of Andrena nitidiusculus provisions nest with pollen of Asteraceae

Foodplant / nest
female of Andrena polita provisions nest with pollen of Asteraceae

Foodplant / nest
female of Andrena rosae provisions nest with pollen of Asteraceae

Foodplant / parasite
sporangium of Bremia lactucae parasitises live leaf of Asteraceae
Remarks: season: 9-10
Other: sole host/prey

Plant / resting place / within
puparium of Calycomyza humeralis may be found in leaf-mine of Asteraceae

Plant / resting place / on
Ceratothrips frici may be found on live Asteraceae

Plant / resting place / within
puparium of Chromatomyia horticola may be found in leaf-mine (end of) of Asteraceae
Other: major host/prey

Foodplant / miner
larva of Chromatomyia syngenesiae mines leaf of Asteraceae
Other: major host/prey

Foodplant / parasite
uredium of Coleosporium tussilaginis parasitises live Asteraceae

Foodplant / nest
female of Colletes daviesanus provisions nest with pollen of Asteraceae

Foodplant / nest
female of Colletes fodiens provisions nest with pollen of Asteraceae

Foodplant / nest
female of Colletes similis provisions nest with pollen of Asteraceae

Foodplant / sap sucker
Corizus hyoscyami sucks sap of Asteraceae
Remarks: Other: uncertain

Foodplant / feeds on
adult of Cryptocephalus aureolus feeds on pollen of Asteraceae
Remarks: season: (4-)5-6(-9)

Foodplant / feeds on
adult of Cryptocephalus hypochaeridis feeds on Asteraceae
Remarks: season: 4-9

Plant / resting place / on
adult of Cryptocephalus sexpunctatus may be found on flower of Asteraceae
Remarks: season: 5-7

Plant / resting place / on
adult of Cryptocephalus violaceus may be found on Asteraceae

Foodplant / nest
female of Dasypoda hirtipes provisions nest with pollen of Asteraceae

Foodplant / saprobe
immersed perithecium of Diaporthe arctii is saprobic on dead, blackened stem of Asteraceae
Remarks: season: 7-11

Foodplant / nest
female of Dufourea minuta provisions nest with pollen of Asteraceae

Foodplant / sap sucker
Enoplops scapha sucks sap of Asteraceae

Foodplant / saprobe
apothecium of Hyalopeziza millepunctata is saprobic on dead stem of Asteraceae
Remarks: season: 5-10

Foodplant / saprobe
immersed pseudothecium of Kalmusia clivensis is saprobic on dead stem of Asteraceae
Remarks: season: 5-6
Other: major host/prey

Foodplant / saprobe
immersed pseudothecium of Leptosphaeria macrospora is saprobic on dead stem of Asteraceae
Remarks: season: 4-6
Other: major host/prey

Foodplant / saprobe
pseudothecium of Leptosphaeria ogilviensis is saprobic on dead stem of Asteraceae
Other: major host/prey

Foodplant / saprobe
partly immersed pseudothecium of Leptosphaeria purpurea is saprobic on dead stem of Asteraceae
Remarks: season: 6-7
Other: major host/prey

Foodplant / miner
larva of Liriomyza strigata mines leaf of Asteraceae
Other: major host/prey

Foodplant / open feeder
adult of Longitarsus luridus grazes on leaf of Asteraceae

Foodplant / open feeder
larva of Longitarsus succineus grazes on leaf of Asteraceae

Foodplant / internal feeder
larva of Napomyza lateralis feeds within stem of Asteraceae
Other: major host/prey

Foodplant / saprobe
immersed pseudothecium of Ophiobolus acuminatus is saprobic on dead stem of Asteraceae
Remarks: season: 3-6
Other: major host/prey

Plant / resting place / within
puparium of Ophiomyia curvipalpis may be found in stem of Asteraceae

Foodplant / parasite
underground tuber of Orobanche artemisiae-campestris parasitises root of Asteraceae

Foodplant / parasite
underground tuber of Orobanche minor var. compositarum parasitises root of Asteraceae

Foodplant / parasite
underground tuber of Orobanche purpurea parasitises root of Asteraceae
Remarks: Other: uncertain
Other: minor host/prey

Foodplant / feeds on
Orthocephalus saltator feeds on Asteraceae

Foodplant / miner
larva of Orthochaetes setiger mines leaf of Asteraceae

Foodplant / nest
female of Osmia leaiana provisions nest with pollen of Asteraceae

Foodplant / nest
female of Panurgus banksianus provisions nest with pollen of Asteraceae

Foodplant / nest
female of Panurgus calcaratus provisions nest with pollen of Asteraceae

Foodplant / miner
larva of Phytoliriomyza arctica mines stem of Asteraceae
Remarks: Other: uncertain

Foodplant / saprobe
pseudothecium of Pleospora ambigua is saprobic on dead stem of Asteraceae

Foodplant / saprobe
immersed pseudothecium of Pleospora phaeocomoides is saprobic on dead stem of Asteraceae
Remarks: season: 2-10
Other: major host/prey

Foodplant / sap sucker
Protrama radicis sucks sap of root of Asteraceae

Foodplant / open feeder
adult of Smaragdina affinis grazes on flowering of Asteraceae
Remarks: season: 5-6

Foodplant / sap sucker
Stictopleurus abutilon sucks sap of Asteraceae

Foodplant / sap sucker
Stictopleurus punctatonervosus sucks sap of seed of Asteraceae
Other: major host/prey

Foodplant / feeds on
male of Thrips hukkineni feeds on live flower of Asteraceae
Remarks: season: 5,7-9

Foodplant / feeds on
larva of Thrips nigropilosus feeds on live Asteraceae
Remarks: season: 5-9

Foodplant / feeds on
female of Thrips physapus feeds on live flower of Asteraceae
Remarks: season: 5,7-9

Plant / resting place / on
male of Thrips pillichi may be found on live flower of Asteraceae
Remarks: season: 6-9

Plant / resting place / on
larva of Thrips validus may be found on live Asteraceae
Remarks: season: 5-9

Foodplant / sap sucker
Trama troglodytes sucks sap of live root of Asteraceae

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Evolution and Systematics

Evolution

Discussion of Phylogenetic Relationships

View Asteraceae Tree

Tree adapted from Panero and Funk 2008

The phylogenetic tree shown on this and subsequent pages is drawn after that reported in Panero and Funk (2008) based on analyses of combined sequence data from multiple chloroplast loci including the genes matK, ndhD, ndhI, ndhF, rbcL, rpoB, exon1 of rpoC1, and the intron and intergenic spacer regions of the trnL-trnF. Each of the major clades of Asteraceae (subfamilial and tribal clades) was inferred in both Maximum Parsimony and Bayesian phylogenetic analyses with significant measures of clade support (bootstrap and posterior probability respectively). Relationships among these clades were also resolved with significant statistical support and were robust to method with the exception of the relationships of Stifftioideae and Wunderlichioideae. The phylogeny of Panero and Funk (2008) represents the best resolved and statistically supported hypothesis of evolutionary relationships among the major clades of the family currently available. Preliminary results from their study (Panero and Funk, 2008) have been used previously as the backbone phylogeny for the construction of a metatree of the family (Funk et al., 2009). The nomenclature used here is consistent with that of NCBI Genbank.

Relationships among the deepest branches of the Asteraceae tree of life have primarily been elucidated through investigations of the chloroplast genome. Comparative nucleotide studies (Kim and Jansen, 1995, Bayer and Starr, 1998, Panero and Funk, 2008) confirmed the original discovery based on restriction fragment polymorphisms (RFLPs) that Barnadesioideae, lacking the 22 kb inversion present in all other sunflowers (Jansen and Palmer, 1987), is sister to all other Asteraceae. A Cichorioideae clade sister to Asteroideae was recovered with weak bootstrap support in the ndhF study of Kim and Jansen (1995) and identified with strong support (bootstrap and posterior probability) in the multi-locus chloroplast study of Panero and Funk (2008). The multi-locus study also recovered strong statistical support for the Mutisioideae, Stifftioideae, Gochnatioideae, Hecastocleidoideae, Carduoideae, Pertyoideae, Gymnarrhenoideae, and Corymbioideae clades. All family-wide molecular phylogenetic studies to date (Kim and Jansen, 1995, Bayer and Starr, 1998, Kim et al., 2005, Panero and Funk, 2008) have shown support for a monophyletic Asteroideae.

Evidence from the nuclear genetic compartment, an analysis of the nuclear ribosomal internal transcribed spacer (nrITS) region (Goertzen et al., 2003), is congruent with chloroplast results in the relationships of Barnadesioideae and Mutisioideae to other Asteraceae, in the monophyly of the Asteroideae, and in the sister relationship of Athroismeae and Heliantheae s.l. Relationships of other major clades of Asteraceae recovered from the nrITS study (strict consensus tree) are not congruent with chloroplast results. However, these may conservatively be viewed as equivocal because of low statistical support (bootstrap proportions).

The phylogenetic tree presented here primarily reflects the evolutionary history of the chloroplast genome. Asteraceae provide some of the best documented examples of hybrid evolution in plants (Rieseberg et al., 2003, Soltis et al. 2008, Timme et al., 2007), but the full extent of reticulation in the evolutionary history of sunflowers is not yet known, nor how closely this genome phylogeny corresponds to the organismal phylogeny of sunflowers.

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There are approximately 23,000 species in the Asteraceae family. Broad agreement exists on the center of biodiversity or evolutionary spatial origin as the High Andes region; however, the time epoch of origination is under dispute. One school of thought places the evolutionary origin of the family at circa 40 million years ago (mya), where an alternative interpretation places the temporal origin at approximately 100 mya. Roberts argues convincingly that the more accurate dating of the family origin is the earlier dating, on the basis of continental drift data.

  • • Roland P.Roberts. 2002. Phylogeny of Ericameria, Chrysothamnus and related genera (Asteraceae: Astereae) based on nuclear ribosomal DNA sequence data . PhD. Dissertation. Louisanna State University
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Functional Adaptations

Functional adaptation

Fibers reinforce hydrostatic skeletons: sunflowers
 

Hydrostatic structures found in sunflowers and other many other organisms serve various functions but almost always use helical fibers as reinforcement.

   
  "With few exceptions, nature uses the second arrangement of fibers for her internally pressurized, water-filled cylinders. These structures (often termed 'hydrostatic skeletons' or 'hydroskeletons' as well as 'hydrostats') have helical reinforcing fibers. And this particular arrangement is no rare or once-evolved thing. It occurs in the stems of young herbaceous (nonwoody) plants such as sunflowers; it provides a wrapping for flatworms (platyhelminths and nemerteans), roundworms (nematodes), and segmented worms (annelids); it stiffens the body wall of sea anemones; it determines the response to muscle contraction of the outer mantle of squids; and it's a major functional component of shark skin. The material of the fibers varies widely, the functions of these hydroskeletons are even more diverse, but the wrapping is almost always helical." (Vogel 2003: 409)
  Learn more about this functional adaptation.
  • Steven Vogel. 2003. Comparative Biomechanics: Life's Physical World. Princeton: Princeton University Press. 580 p.
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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage

Barcode of Life Data Systems (BOLD) Stats
                                        
Specimen Records:9,411Public Records:4,915
Specimens with Sequences:7,544Public Species:2,304
Specimens with Barcodes:7,059Public BINs:0
Species:3,311         
Species With Barcodes:2,662         
          
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Source: Barcode of Life Data Systems (BOLD)

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Statistics of barcoding coverage: Asteraceae Espinoza5656

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 6
Species With Barcodes: 1
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Source: Barcode of Life Data Systems (BOLD)

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Statistics of barcoding coverage: Asteraceae Jorge197

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Public Records: 0
Specimens with Barcodes: 1
Species With Barcodes: 1
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Statistics of barcoding coverage: Asteraceae A.guadamuz339

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 2
Species With Barcodes: 1
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Statistics of barcoding coverage: Asteraceae A.guadamuz322

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 1
Species With Barcodes: 1
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Statistics of barcoding coverage: Asteraceae jorge141

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 4
Species With Barcodes: 1
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Statistics of barcoding coverage: Asteraceae Espinoza5721

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 2
Species With Barcodes: 1
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Statistics of barcoding coverage: Asteraceae Espinoza5707

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 2
Species With Barcodes: 1
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Statistics of barcoding coverage: Asteraceae Espinoza5746

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 1
Species With Barcodes: 1
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Barcode data

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Locations of barcode samples

Collection Sites: world map showing specimen collection locations for Asteraceae

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Wikipedia

Asteraceae

The Asteraceae or Compositae (commonly referred to as the aster, daisy, composite,[4] or sunflower family) are an exceedingly large and widespread family of flowering plants (Angiospermae).[5][6] The group has more than 23,000 currently accepted species, spread across 1,620 genera (list) and 12 subfamilies. In terms of numbers of species, the Asteraceae are rivaled only by the Orchidaceae.[5][7] (Which of the two families is actually larger is unclear, owing to uncertainty about exactly how many species exist in each family.) The main feature of the family is the composite flower type in the form of capitula surrounded by involucral bracts. The name "Asteraceae" comes from Aster, the most prominent genus in the family, that derives from the Greek ἀστήρ, meaning star, and is connected with its inflorescence star form. As for the term "Compositae", more ancient but still valid, it obviously makes reference to the fact that the family is one of the few angiosperm ones to have composite flowers.[8] This family has a remarkable ecological and economical importance and is present from the polar regions to the tropics, colonizing all available habitats. The Asteraceae may represent as much as 10% of autochthonous flora in many regions of the world.

Most members of Asteraceae are herbaceous, but a significant number are also shrubs, vines, or trees. The family has a worldwide distribution and is most common in the arid and semiarid regions of subtropical and lower temperate latitudes.[9]

The Asteraceae are an economically important family. Some members provide products, including cooking oils, lettuce, sunflower seeds, artichokes, sweetening agents, coffee substitutes, and herbal teas. Several genera are popular with the horticultural community, including marigold, pot marigold (also known as calendula), cone flowers, various daisies, fleabane, chrysanthemums, dahlias, zinnias, and heleniums. Asteraceae are important in herbal medicine, including Grindelia, Echinacea, yarrow, and many others.[10] A number of species have come to be considered invasive, including, most notably in North America, dandelion, which was originally introduced by European settlers who used the young leaves as a salad green.[11]

Etymology[edit]

The Latin name "Asteraceae" is derived from the type genus Aster, which is a Greek term that means "star".[12] "Compositae", an older but still valid name,[13] means "composite" and refers to the characteristic inflorescence, a special type of pseudanthium found in only a few other angiosperm families. The study of this family is known as synantherology.

The vernacular name "daisy", widely applied to members of this family, is derived from its Old English name: dægesege, from dæges eage, meaning "day's eye". This is because the petals (of Bellis perennis) open at dawn and close at dusk.

Distribution[edit]

Asteraceae have a cosmopolitan distribution, and are found everywhere except Antarctica and the extreme Arctic. They are especially numerous in tropical and subtropical regions (notably Central America, eastern Brazil, the Andes, the Mediterranean, the Levant part of the Middle East, southern Africa, central Asia, and southwestern China).[7]

Taxonomy[edit]

Compositae were first described in 1792 by the German botanist Paul Dietrich Giseke.[14] Traditionally, two subfamilies were recognised: Asteroideae (or Tubuliflorae) and Cichorioideae (or Liguliflorae). The latter has been shown to be extensively paraphyletic, and has now been divided into 11 subfamilies, but the former still stands. The phylogenetic tree presented below is based on Panero & Funk (2002).[15] The diamond denotes a very poorly supported node (<50% bootstrap support), the dot a poorly supported node (<80%).[5]



Barnadesioideae: 9 genera, 93 species. South America, mainly the Andes.




Stifftioideae: South America and Asia.



Mutisioideae: 58 genera, 750 species. South America.



Wunderlichioideae: 8 genera, 24 species, mostly in Venezuela and Guyana




Gochnatioideae: 4 or 5 genera, 90 species.




Hecastocleidoideae: Only Hecastocleis shockleyi. Southwestern United States.




Carduoideae: 83 genera, 2,500 species. Worldwide.




Pertyoideae: 5 or 6 genera, 70 species.




Gymnarrhenoideae: Only Gymnarrhena micrantha. Northern Africa.



Cichorioideae: 224 genera, 3,200 species. Worldwide.




Corymbioideae: Only the genus Corymbium, with 9 species.



Asteroideae: 1,130 genera and 16,200 species. Worldwide.














It is noteworthy that the four subfamilies Asteroideae, Cichorioideae, Carduoideae and Mutisioideae contain 99% of the species diversity of the whole family (approximately 70%, 14%, 11% and 3% respectively).

Because of the morphological complexity exhibited by this family, agreeing on generic circumscriptions has often been difficult for taxonomists. As a result, several of these genera have required multiple revisions.[16]

Characteristics[edit]

Asteraceae are mostly herbaceous plants, but some shrubs, trees and climbers do exist. Asteraceae are generally easy to distinguish from other plants, mainly because of their characteristic inflorescence and other shared characteristics.[16] However, determining genera and species is notoriously difficult (see "damned yellow composite" for example).

Roots and stems[edit]

Asteraceae generally produce taproots, but sometimes they possess fibrous root systems. Stems are generally erect, but can be prostrate to ascending. Some species have underground stems in the form of caudices or rhizomes. These can be fleshy or woody depending on the species.[9]

Leaves[edit]

The leaves and the stems very often contain secretory canals with resin or latex (particularly common among the Cichorioideae). The leaves can be alternate, opposite, or whorled. They may be simple, but are often deeply lobed or otherwise incised, often conduplicate or revolute. The margins can be entire or lobed or toothed.

Flowers[edit]

Floral heads[edit]

In many plants of the Asteraceae family, what appears to be a single flower is actually a cluster of much smaller flowers.[17] The overall appearance of the cluster, as a single flower, functions in attracting pollinators in the same way as the structure of an individual flower in some other plant families.[17] The older family name, Compositae, comes from the fact that what appears to be a single flower, is actually a composite of smaller flowers.[17] The "petals" or "sunrays" in a sunflower head are actually individual strap-shaped[18] flowers called "ray flowers", and the "sun disk" is made of smaller circular shaped individual flowers called "disc flowers".[17] The word aster means "star" in Greek, referring to the appearance of some family members, as a "star" surrounded by "rays".[17] The cluster of flowers that may appear to be a single flower, is called a head.[17] The entire head may move tracking the sun, like a "smart" solar panel, which maximizes reflectivity of the whole unit and can thereby attract more pollinators.[17]

A ray flower is a 3-tipped (3-lobed), strap-shaped, individual flower in the head of some members of the Asteraceae family.[17][18] Sometimes a ray flower has 2 tips (or 2-lobes).[17] The corolla of the ray flower may have 2 tiny teeth opposite the 3 lobed strap, or tongue, indicating evolution by fusion from an originally 5 part corolla.[17] Sometimes, the 3:2 arrangement is reversed, with 2 tips on the tongue, and 0 or 3 tiny teeth opposite the tongue.[17] A ligulate flower is a 5 tipped, strap-shaped, individual flower in the heads of other members.[17] A ligule is the strap-shaped tongue of the corolla of either a ray flower or of a ligulate flower.[18] A disk flower is a radially symmetric (i.e., with identical shaped petals arranged in circle around the center) individual flower in the head, which is ringed by ray flowers when both are present.[17][18] Sometimes ray flowers may be slightly off from radial symmetry, or weakly bilaterally symmetric, as in the case of desert pincushions Chaenactis fremontii.[17]

At the base of the head, and surrounding the flowers before opening, is a bundle of sepal-like bracts or scales called phyllaries, which together form the involucre that protects the individual flowers in the head before opening.[17] The individual heads have the smaller individual flowers arranged on a round or dome-like structure called the receptacle.[17] The flowers mature first at the outside, moving toward the center, with the youngest in the middle.[17]

The individual flowers in a head have 5 fused petals (rarely 4), but instead of sepals, have threadlike, hairy, or bristly structures called pappus, which surround the fruit and can stick to animal fur or be lifted by wind, aiding in seed dispersal.[17] The whitish fluffy head of a dandelion commonly blown on by children, is made of the pappus, with tiny seeds attached at the ends, whereby the pappus provides a parachute like structure to help the seed be carried away in the wind.[17]

A radiate head has disc flowers surrounded by ray flowers.[17] A ligulate head has all ligulate flowers.[17] When a sunflower family flower head has only disk flowers that are sterile, male, or have both male and female parts, it is a discoid head.[17] Disciform heads have only disc flowers, but may have two kinds (male flowers and female flowers) in one head, or may have different heads of two kinds (all male, or all female).[17] Pistillate heads have all female flowers. Staminate heads have all male flowers.[17]

Sometimes, but rarely, the head contains only a single flower, or has a single flowered pistillate (female) head, and a multi-flowered male staminate (male) head.[17]

Floral structures[edit]

Flower diagram of Carduus (Carduoideae) shows (outermost to innermost): subtending bract and stem axis; fused calyx; fused corolla; stamens fused to corolla; gynoecium with two carpels and one locule
A typical Asteraceae flower head (here Bidens torta) showing the individual flowers
Ray floret (as in Cichorioideae, and the outer florets in Asteroideae)
Disc floret (as in Asteroideae)

The most evident characteristic of Asteraceae is perhaps their inflorescence: a specialised capitulum, technically called a calathid or calathidium, but generally referred to as flower head or, alternatively, simply capitulum.[19] The capitulum is a contracted raceme composed of numerous individual sessile flowers, called the florets, all sharing the same receptacle.

The capitulum of Asteraceae has evolved many characteristics that make it look superficially like a single flower. This type of flower-like inflorescence is fairly widespread amongst angiosperms, and has been given the name of pseudanthia.

A set of bracts forms an involucre surrounding the base of the capitulum. These are called "phyllaries", or "involucral bracts". They may simulate the sepals of the pseudanthium. These are mostly herbaceous but can also be brightly coloured (e.g. Helichrysum) or have a scarious (dry and membranous) texture. The phyllaries can be free or fused, and arranged in one to many rows, overlapping like the tiles of a roof (imbricate) or not (this variation is important in identification of tribes and genera).

Each floret may itself be subtended by a bract, called a "palea" or "receptacular bract". These bracts as a group are often called "chaff". The presence or absence of these bracts, their distribution on the receptacle, and their size and shape are all important diagnostic characteristics for genera and tribes.

The florets have five petals fused at the base to form a corolla tube and they may be either actinomorphic or zygomorphic. Disc florets are usually actinomorphic, with five petal lips on the rim of the corolla tube. The petal lips may be either very short, or long, in which case they form deeply lobed petals. The latter is the only kind of floret in the Carduoideae, while the first kind is more widespread. Ray florets are always highly zygomorphic and are characterised by the presence of a ligule, a strap-shaped structure on the edge of the corolla tube consisting of fused petals. In the Asteroideae and other minor subfamilies these are usually borne only on florets at the circumference of the capitulum and have a 3+2 scheme – above the fused corolla tube, three very long fused petals form the ligule, with the other two petals being inconspicuously small. The Cichorioidea has only ray florets, with a 5+0 scheme – all five petals form the ligule. A 4+1 scheme is found in the Barnadesioideae. The tip of the ligule is often divided into teeth, each one representing a petal. Some marginal florets may have no petals at all (filiform floret).

The calyx of the florets may be absent, but when present is always modified into a pappus of two or more teeth, scales or bristles and this is often involved in the dispersion of the seeds. As with the bracts, the nature of the pappus is an important diagnostic feature.

There are usually five stamens. The filaments are fused to the corolla, while the anthers are generally connate (syngenesious anthers), thus forming a sort of tube around the style (theca). They commonly have basal and/or apical appendages. Pollen is released inside the tube and is collected around the growing style, and then, as the style elongates, is pushed out of the tube (nüdelspritze).

The pistil consists of two connate carpels. The style has two lobes. Stigmatic tissue may be located in the interior surface or form two lateral lines. The ovary is inferior and has only one ovule, with basal placentation.

Fruits and seeds[edit]

The fruit of the Asteraceae is achene-like, and is called a cypsela (plural cypselae). Although there are two fused carpels, there is only one locule, and only one seed per fruit is formed. It may sometimes be winged or spiny because the pappus, which is derived from calyx tissue often remains on the fruit (for example in dandelion). In some species, however, the pappus falls off (for example in Helianthus). Cypsela morphology is often used to help determine plant relationships at the genus and species level.[20] The mature seeds usually have little endosperm or none.[16]

Metabolites[edit]

Asteraceae generally store energy in the form of inulin. They produce iso/chlorogenic acid, sesquiterpene lactones, pentacyclic triterpene alcohols, various alkaloids, acetylenes (cyclic, aromatic, with vinyl end groups), tannins. They have terpenoid essential oils which never contain iridoids.[5]

Evolution[edit]

Diversification of Asteraceae appears to have taken place roughly 42-36 million years ago, the stem group perhaps being up to 49 million years old.[5]

It is still unknown whether the precise cause of their great success was the development of the highly specialised capitulum, their ability to store energy as fructans (mainly inulin), which is an advantage in relatively dry zones, or some combination of these and possibly other factors.[5]

Ecology[edit]

Seeds are dispersed by the wind in Carlina
Epizoochory in Bidens tripartita

Asteraceae are especially common in open and dry environments.[16]

Many members of the Asteraceae are pollinated by insects, which explains their value in attracting beneficial insects, but anemophyly is also present (e.g. Ambrosia, Artemisia). There are many apomictic species in the family.

Seeds are ordinarily dispersed intact with the fruiting body, the cypsela. Wind dispersal is common (anemochory) assisted by a hairy pappus. Another common variation is epizoochory, in which the dispersal unit, a single cypsela (e.g. Bidens) or entire capitulum (e.g. Arctium) provided with hooks, spines or some equivalent structure, sticks to the fur or plumage of an animal (or even to clothes, like in the photo) just to fall off later far from its mother plant.

Uses[edit]

Commercially important plants in the Asteraceae include the food crops Lactuca sativa (lettuce), Cichorium (chicory), Cynara scolymus (globe artichoke), Helianthus annuus (sunflower), Smallanthus sonchifolius (yacón), Carthamus tinctorius (safflower) and Helianthus tuberosus (Jerusalem artichoke).

Many members of the family are grown as ornamental plants for their flowers, and some are important ornamental crops for the cut flower industry. Some examples are Chrysanthemum, Gerbera, Calendula, Dendranthema, Argyranthemum, Dahlia, Tagetes, Zinnia, and many others.

Other commercially important species include Compositae used as herbs and in herbal teas and other beverages. Chamomile, which comes from two different species, the annual Matricaria recutita (or German chamomile) and the perennial Chamaemelum nobile (also called Roman chamomile). Calendula (also called the pot marigold) is grown commercially for herbal teas and the potpourri industry. Echinacea (Echinacea purpurea) is used as a medicinal tea. Winter tarragon (also called Mexican mint marigold), or Tagetes lucida, is commonly grown and used as a tarragon substitute in climates where tarragon will not survive. Finally, the wormwood genus Artemisia includes absinthe (A. absinthium) and tarragon (A. dracunculus).

Compositae have also been used for industrial purposes. Common in all commercial poultry feed, marigold (Tagetes patula) is grown primarily in Mexico and Central American nations. Marigold oil, extracted from Tagetes minuta, is used in the cola and cigarette industries.

Plants in Asteraceae are medically important in areas that don't have access to Western medicine. They are also commonly featured in medical and phytochemical journals because the sesquiterpene lactone compounds contained within them are an important cause of allergic contact dermatitis. Allergy to these compounds is the leading cause of allergic contact dermatitis in florists in the US.[21] Pollen from ragweed Ambrosia is among the main causes of so-called hay fever in the United States.[22]

Many members of Asteraceae are copious nectar producers and are useful for evaluating pollinator populations during their bloom. Centaurea (knapweed), Helianthus annuus (domestic sunflower), and some species of Solidago (goldenrod) are major "honey plants" for beekeepers. Solidago produces relatively high protein pollen, which helps honey bees over winter.[citation needed]

Some members of the Asteraceae are economically important as weeds. Notable in the United States are the ragwort, Senecio jacobaea, groundsel Senecio vulgaris, and Taraxacum (dandelion).

The genera Chrysanthemum, Pulicaria, Tagetes, and Tanacetum contain species with useful insecticidal properties.[citation needed]

Parthenium argentatum (guayule) is a source of hypoallergenic latex.

Genera[edit]

See also[edit]

References[edit]

  1. ^ Scott, L.; Cadman, A; McMillan, I (2006). "Early history of Cainozoic Asteraceae along the Southern African west coast". Review of Palaeobotany and Palynology 142: 47. doi:10.1016/j.revpalbo.2006.07.010. 
  2. ^ Angiosperm Phylogeny Group (2009), "An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG III", Botanical Journal of the Linnean Society 161 (2): 105–121, doi:10.1111/j.1095-8339.2009.00996.x, retrieved 10 December 2010 
  3. ^ Germplasm Resources Information Network (GRIN). "Family: Asteraceae Bercht. & J. Presl, nom. cons.". Taxonomy for Plants. USDA, ARS, National Genetic Resources Program, National Germplasm Resources Laboratory, Beltsville, Maryland. Retrieved 12 June 2008. 
  4. ^ Great Basin Wildflowers, Laird R. Blackwell, 2006, p. 275
  5. ^ a b c d e f Stevens, P. F. (2001 onwards) Angiosperm Phylogeny Website. Version 13, updated: 04/19/2014 19:57:49
  6. ^ Jeffrey, C. 2007. Compositae: Introduction with key to tribes. Pages 61-87 in Families and Genera of Vascular Plants, vol. VIII, Flowering Plants, Eudicots, Asterales (J. W. Kadereit and C. Jeffrey, eds.). Springer-Verlag, Berlin
  7. ^ a b Panero, J.L., Crozier, B.S. Tree of Life - Asteraceae
  8. ^ International Code of Botanical Nomenclature. In point 18/5 states: "The following names, used traditionally, are considered valid: Compositae (Asteraceae...).
  9. ^ a b Barkely, T.M., Brouillet, L., Strother, J.L. (2006) Flora of North America - Asteraceae" http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=10074
  10. ^ Dr. Duke's Phytochemical and Ethnobotanical Databases
  11. ^ "dandelion Taraxacum officinale". Invasive Plant Atlas of the United States. Retrieved 10 September 2012. 
  12. ^ Merriam-Webster Dictionary. Aster. http://www.merriam-webster.com/dictionary/aster
  13. ^ International Code of Botanical Nomenclature - Article 18.5 http://ibot.sav.sk/icbn/main.htm
  14. ^ Solbrig, O.T. (1963) Subfamilial Nomenclature of Compositae. Taxon 12: 229-235 JSTOR 1216917
  15. ^ Panero, J.L., Funk, V.A. (2002) Toward a phylogenetic subfamilial classification for the Compositae (Asteraceae). Proc. Biol. Soc. Wash. 115: 909-922.
  16. ^ a b c d Judd, W.S., Campbell, C.S., Kellogg, E.A., Stevens, P.F. (2007) Plant Systematics: A Phylogenetic Approach. Sinauer Associates, Sunderland.
  17. ^ a b c d e f g h i j k l m n o p q r s t u v w x y Sia Morhardt, Emil Morhardt, California Desert Flowers, University of California Press, pp. 29-32
  18. ^ a b c d Pam MacKay, Mojave Desert Wildflowers, illustration p. 35
  19. ^ Usher, G. (1966) A dictionary of botany, including terms used in bio-chemistry, soil science, and statistics. LCCN 66 0 25447
  20. ^ McKenzie, R.J., Samuel, J., Muller, E.M., Skinner, A.K.W., Barker, N.P. (2005). "Morphology Of Cypselae In Subtribe Arctotidinae (Compositae–Arctotideae) And Its Taxonomic Implications". Annals of the Missouri Botanical Garden 92 (4): 569–594. 
  21. ^ Odom, R.B., James, W.D., Berger, T.G. (2000). Andrews' Diseases of the Skin: Clinical Dermatology. W.B. Saunders Company. pp. 1135 pages. ISBN 0-7216-5832-6. 
  22. ^ Asthma and Allergy Foundation of America. Ragweed Allergy. http://www.aafa.org/display.cfm?id=9&sub=19&cont=267
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