EudicotsLouis P Ronse De Craene, Royal Botanic Garden Edinburgh, Edinburgh, UK

Based in part on the previous version of this eLS article ‘Eudicots’ (2002)by Douglas E Soltis and Pamela S Soltis.

Eudicots represent the largest clade of flowering plants,

comprising approximately 75% of all species and charac-

terisedbypollenhavingthreeapertures. Eudicotsconsistof

a basal grade and a large (core eudicot) clade, which com-

prises the majority of species. Evolution of flowers in core

eudicots is highly diverse and is driven by repeated diver-

sifications of pollination mechanisms. Two major clades,

the Asterids and Rosids, have evolved separately and have

attained a high level of diversity. Eudicots are a highly

successful groupofplants,occupyingalmostallhabitatson

earth. Apart from Poaceae in the monocots, the major food

cropsare found inthecore eudicots. Flowers of eudicotsare

mostly with parts in five and with a differentiated perianth

of sepals and petals. Specific pollination mechanisms have

led to groups with specialised animal-pollinated zygo-

morphic flowers (Leguminosae and Lamiales) or wind-

pollinated apetalous flowers (Fagales and Caryophyllales).

Dispersal mechanisms are also highly diverse.

Introduction

Until fairly recently, classifications of the flowering plantsor angiosperms have recognised two major groups, thedicots (short for dicotyledons; class Magnoliopsida) andthe monocots (monocotyledons; class Liliopsida). Thedicots are distinguished from monocots by a suite ofmorphological and anatomical features, all of which aresubject to exception. For example, as the names of thegroups suggest, dicots possess two seed leaves or coty-ledons, whereas monocots have a single cotyledon. How-ever, even thismajor characteristic has exceptions.See also:Angiosperms; Monocotyledons

Although the monocot–dicot division has long beenrecognised, recent phylogenetic studies (based on

deoxyribonucleic acid (DNA) sequence data as well asmorphological, anatomical, chemical and other non-DNAcharacters) demonstrate clearly that this split does notaccurately reflect the evolutionary history of floweringplants. The monocots, as well as eudicots, are embeddedamong clades of early diverging lineages of floweringplants, the basal angiosperms – all of which have beenrecognised as part of the traditional dicots. Botanists havelong theorised that the monocots were derived from anancient group of ‘dicots’ and arose during the early diver-sification of the angiosperms. Phylogenetic trees derivedfrom molecular data thus confirm this longstandinghypothesis. See also: History of Plant SciencesThe majority of angiosperms form a distinct clade

referred to as the eudicots (or ‘true dicots’ or ‘tricolpates’)(Figure 1). Eudicots are characterised by pollen grains thatpossess three apertures (referred to as triaperturate pollen),or by pollen types derived from triaperturate pollen; noother morphological or anatomical structures that markthis grouphave been identified so far, although the eudicotsare strongly supported by analyses based on DNAsequence data. The eudicots do not correspond to the tra-ditional dicots, but instead are a subset of the dicots,whereasmonocots emerge as a subset of basal angiospermsand share more characters with them, such as trimerousflowers (with parts in three) and pollen grains that have asingle aperture (referred to as uniaperturate pollen). Basalangiosperms (see Figure 1) contain ancient families such asMagnoliaceae, Lauraceae and Piperaceae formerlygrouped as Magnoliidae by Cronquist (1981). See also:Laurales; Magnoliales; PiperalesThus, there is no clear monocot–dicot split in the

angiosperms. Whereas ‘monocot’ remains a useful term,corresponding to a clade of approximately 62 000 species,‘dicot’ does not represent a monophyletic group offloweringplants and shouldbe abandoned. It ismore usefulto refer to ‘eudicots’, which represent a well-marked cladeof flowering plants.

Composition

The eudicots contain approximately 75%of all angiospermspecies, or roughly 200 000 species distributed among

Introductory article

Article Contents

. Introduction

. Composition

. Phylogeny

. Flower Morphology and Evolution

. Fossil History

. Biogeography and Ecology

. Economic Importance: Crops and Ornamentals

Online posting date: 15th May 2012

eLS subject area: Plant Science

How to cite:Ronse De Craene, Louis P (May 2012) Eudicots. In: eLS. John Wiley &Sons, Ltd: Chichester.

DOI: 10.1002/9780470015902.a0003684.pub2

eLS & 2012, John Wiley & Sons, Ltd. www.els.net 1

approximately 308 families and over 30 orders (APG,2009). The eudicots can be divided into two groups: a basaleudicot grade with Ranunculales as major order, and alarge clade of core eudicots including the majority of spe-cies. Because there are so many families and genera of coreeudicots, it is not possible to list themall here.However, theeudicots includemost familiar angiosperm trees and shrubsandmany herbaceous groups (Table 1; Figure 1). Some of thelarger, better known families of eudicots include theRosaceae (rose family), Fabaceae (pea or legume family),

Brassicaceae (mustard family), Ranunculaceae (buttercupfamily), Ericaceae (heath or rhododendron family), Apia-ceae (parsley family), Asteraceae (sunflower family)and Lamiaceae (mint family). The eudicots include notonly most of our familiar temperate trees, including theFagaceae (oak or beech family), Betulaceae (birch family),Juglandaceae (walnut or hickory family), Aceraceae(maple family) and Platanaceae (plane tree or sycamorefamily), but also large, mainly tropical families, includingRubiaceae (coffee family), Euphorbiaceae (spurge family),

Basal Angiosperms

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Monocots

Ceratophyllales

Ranunculales

Proteales

Buxales

Trochodendrales

Gunnerales

Dilleniales

Malvales

Brassicales

Huerteales

Sapindales

Crossosomatales

Geraniales

Myrtales

Cucurbitales

Fagales

Rosales

Fabales

Oxalidales

Malpighiales

Celastrales

Saxifragales

Santalales

Berberidopsidales

Caryophyllales

Cornales

Ericales

Apiales

Asterales

Dipsacales

Solanales

Gentianales

Lamiales

Figure 1 Summary tree showing the relationships among major groups of angiosperms with a focus on eudicots. Based on APG III (2009) and Soltis et al.

(2011).

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Malvaceae (mallow family) and Solanaceae (potatofamily).

Phylogeny

Great progress has beenmade in resolving the phylogenyofangiosperms in the last decade, especially of the majorclades of eudicots (e.g.Wang et al., 2009; Soltis et al., 2011).A well-resolved phylogeny for angiosperms is of broadutility in that many biological comparisons are best madein light of a firm understanding of angiosperm relation-ships and in that it allows for the recognition of obviousand new morphological characters to identify the clades.

These phylogenetic studies indicate that the eudicotscomprise several distinct clades (Figure 1). The earliestbranches of eudicots (basal or early diverging eudicots)include theRanunculales, an order that contains suchwell-known families as the Ranunculaceae (buttercup family)and Papaveraceae (poppy family: Figure 2a); the Proteales,

which include the Platanaceae (plane tree or sycamorefamily), Nelumbonaceae (the lotus); and Proteaceae (Pro-tea and Macadamia nut); Sabiaceae; Trochodendraceaeand the Buxaceae (boxwood or box family). The basalgrade of eudicots appears intermediate between basalangiosperms and core eudicots in sharing advanced andprimitive characters. Especially in Ranunculaceae one seestransitions between spiral an whorled flowers, a differen-tiation of the perianth in sepals and nectariferous petals,and several types of merisms, of which pentamery is lesscommon (seeDrinnan et al., 1994; Soltis et al., 2005; RonseDe Craene, 2010).Following these early branches of eudicots is a large clade,

the ‘core eudicots’ that comprises the vast majority of eudi-cots (see Figure 1). Within core eudicots there are two majorclades and a few smaller ones. The main branches of coreeudicots are the rosids and asterids, which are huge groups,each containing roughly one-third of the known speciesof angiosperms. In addition to the major clades of coreeudicots are other smaller clades such asBerberidopsidales,

Table 1 Some of the major clades of eudicots and representative eudicot families, with common name and approximate number

of species

Major clade Representative families (with common name)

Approximate number

of species

Rosid Rosaceae (rose family) 3000

Leguminosae (pea or legume family) 19 500

Brassicaceae (Cruciferae or mustard family) 3400

Fagaceae (beech or oak family) 970

Cucurbitaceae (pumpkin or gourd family) 940

Euphorbiaceae (spurge family) 6500

Juglandaceae (walnut or hickory family) 61

Begoniacae (begonia family) 1400

Geraniaceae (geranium family) 650

Malvaceae (cotton family) 5000

Betulaceae (birch family) 140

Rutaceae (Citrus family) 1900

Asterid Cornaceae (dogwood family) 80

Ericaceae (heath family) 3850

Primulaceae (cowslip family) 2575

Lamiaceae (Labiatae or mint family) 6500

Solanaceae (Nightshade family) 2450

Asteraceae (Compositae or sunflower family) 23 600

Apiaceae (Umbelliferae or parsley family) 3500

Acanthaceae (acanthus family) 3175

Rubiaceae (coffee family) 10900

Caprifoliaceae (honeysuckle family; incl. teasel and Valerian families) 900

Caryophyllales Cactaceae (cactus family) 1210

Caryophyllaceae (carnation or pink family) 2630

Aizoaceae (mesembryanthemum family) 1860

Polygonaceae (buckwheat or rhubarb family) 1200

Amaranthaceae (amaranth family) 2000

Ranunculales Ranunculaceae (buttercup family) 2100

Papaveraceae (poppy family) 820

Based on Mabberley (2008).

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(a)

(c)

(e)

(g)

(b)

(d)

(f)

(h)

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Saxifragales, Caryophyllales, Santalales, Dilleniales andGunnerales (Figure 1).

The transition between basal eudicots and core eudicotsremains unclear on a morphological basis. In many basaleudicots there is a tendency for developing stronglyreduced dimerous flowers without perianth or with anundifferentiated perianth. This culminates in Gunnerales,the basalmost clade of core eudicots (Figure 2b). Gunneralesare treated as part of core eudicots because of strongmolecular support, but they fit much better with the basaleudicots on a morphological basis (Wanntorp and RonseDe Craene, 2005; Endress, 2010). Most core eudicots havepentamerous flowers with a differentiated perianth, and atleast one or two whorls of stamens. The possible origins ofcore eudicot flowers have been discussed in von Balthazarand Endress (2002) and Wanntorp and Ronse De Craene(2005). Ronse De Craene (2004) suggested that spiralflowers with undifferentiated perianth as reflected in Ber-beridopsidaceae (Figure 3a) might function as prototype forfloral evolution in core eudicots. Although Berber-idopsidaceae are part of a derived clade of core eudicots,their floral Bauplan may be a retained ancient structure.Following the origin and initial diversification of theeudicots, a rapid radiation occurred, yielding the extantgroups of core eudicots seen today. This hypothesis of arapid radiation of the core eudicot lineages agrees with thefossil record (see below).

Relationships among the core eudicots have beenrecently clarified, thanks to intensive study using severalsources of DNA sequence data (Wang et al., 2009; Soltiset al., 2011). Two larger subclades can be recognised, rosidsand asterids (Figure 1).

Rosids contain two main subclades, Malvids (Malvidaeor eurosid II) andFabids (Fabidae or eurosids I), followingdivergence of an early branching Saxifragales. Saxifragalesare an assemblage of diverse families, including woodymembers of the former subclass Hamamelidae of Cron-quist (1981) (e.g. Hamamelidaceae or witch hazels) andmainly herbaceous families (Crassulaceae, Paeoniaceaeand Saxifragaceae; Figure 2d). In most cases rosids can bereadily identified by their floral structure (free petals, twostamen whorls and 3–5 carpels: Figure 4a) and by recurringtrends in the flower morphology, although there is still along way to go to find clearcut synapomorphies (Endress,2010; Endress and Matthews, 2006; Ronse De Craene,2010).

The Fabid subclade contains several orders grouped intotwo main clades, a nitrogen-fixing clade (with several mem-bers having nitrogen-fixing bacteria in root nodules: e.g.Leguminosae) and a Celastrales–Oxalidales–Malpighialesclade, as well as a small Zygophyllales. TheMalpighiales are

a huge order with 35 families and about 16 000 species,containing families such as Violaceae (violet family) andEuphorbiaceae (spurge family: Figure 2g). Larger orders ofthe nitrogen-fixing clade are Fabales (Leguminosae withzygomorphic flowers: Figure 2e), Rosales (mainly windpollinated and apetalous, except Rosaceae), Cucurbitales(with gourds and begonias) and Fagales (mainly temperatewind-pollinated treeswith complex dispersalmechanisms).TheMalvid subclade contains a few smaller orders, such

as Geraniales (with Geraniaceae: Figure 2f) and Myrtales(withMyrtaceae andLythraceae: Figure2c), and three large,mainly (sub)tropical orders, such as Sapindales, Brassi-cales and Malvales. Brassicales contain economicallyimportant families such as Capparaceae (caper family:Figure 2h) and Brassicaceae (mustard family), whereasMalvales contain the large family Malvaceae, source offibres and cotton.Asterids are related with Berberidopsidales, Santalales

and Caryophyllales. A strong character linking thesegroups are ovules with relatively thin nucelli, culminatingin tenuinucellate unitegmic ovules in major orders ofasterids (Endress, 2010). Santalales contain mainly hemi-parasitic plants and flowers have a tendency to lose thecalyx, with stamens opposite the petals and a reduction ofovular tissue. Caryophyllales represents the third largestclade of eudicots, containing the traditional Cen-trospermae or core Caryophyllales, and Polygonales (ornoncore Caryophyllales). Core Caryophyllales have beenrecognised for a long time (see Cronquist, 1981), sharingseveral morphological characters (e.g. perispermous seeds,campylotropous ovules, free-central placentation and aspecific kind of sieve tube plastids). The noncore Car-yophyllales contain knotweeds (Polygonaceae), salt-toler-ant plants (Tamarix) and a group of carnivorous plants(Nepenthes and Drosera). Several Caryophyllales familiesare adapted to extreme dry or saline conditions and there isa repeated evolution of petals from previously apetalousflowers. Petalsmaybederived fromstamens, from sepals orfrom bracts (Ronse De Craene, 2007, 2010; Brockingtonet al., 2009).Asterids contain a basal grade with two orders Cornales

(with dogwoods and Hydrangeas) and Ericales (with Eri-caceae: Figure 3e and Primulaceae), and two main clades,Lamiids (Lamiidae or euasterids I) and Campanulids(Campanulidae or euasterids II).Within asterids the basal grade appears to be inter-

mediate between rosids and other asterids in having avariable flower structure. The higher clades are morehomogenous with a petal tube fused with a single stamenwhorl opposite the sepals (Figure 4b). Within Lamiids, twoorders are mainly actinomorphic with tubular flowers

Figure 2 Illustrations of flowers in the early diverging eudicots and rosids. (a) Papaver somniferum (Papaveraceae). Note four petals in two whorls. (b)

Gunnera magellanica (Gunneraceae). Male inflorescence with small apetalous flowers. (c) Punica granatum (Lythraceae). Young fruit; note inferior ovary and

hypanthium with sepals. (d) Saxifraga cotyledon (Saxifragaceae). Flower with two whorls of stamens. (e) Bauhina variegata (Leguminosae), zygomorphic

flower. (f) Erodium�willkommianum (Geraniaceae). Slightly zygomorphic flower. (g) Euphorbia punicea (Euphorbiaceae). Pseudanthium from above. Note

terminal female flower surrounded by male flowers and glands. (h) Capparis spinosa (Capparaceae). Lateral view of flower with many stamens and

gynoecium on gynophore.

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(a)

(c)

(f) (g)

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(Gentianales and Solanales; Figure 3g), whereas Lamialeshas flowers with a high incidence of zygomorphy (Figure 3f

and Figure 4b). Within Campanulids there is a general ten-dency for inferior ovaries with few ovules and a reductionof sepals (in Asterales, Dipsacales and Apiales). EspeciallyAsteraceae (composites) and Apiaceae (umbellifers) arehighly successful herbs with complex inflorescences con-taining many flowers. See also: Asterids; Brassicales(Mustard); Cornales (Dogwood); Dipsacales (Honey-suckle); Fagales (Oak); Gentianales (Coffees, Dogbanes,Gentians and Milkweeds); Malpighiales; Malvales (Mal-low); Oxalidales; Rosales (Rose); Santalales (IncludingMistletoes); Saxifraga (Saxifrages)

Flower Morphology and Evolution

Although monocots generally have trimerous flowers withundifferentiated perianth, and basal angiosperms have amuch variable merism, the majority of eudicots have pen-tamerous or tetramerous flowers with a differentiatedperianth. Evolution of flowers went hand in hand with ahigh diversification of pollination and dispersal mech-anisms, including evolution of wind pollination or variousassociations of flowers with animal pollinators of all kinds.However, in monocots a similar sophistication andsynorganisation can be found, albeit it originated inde-pendently (Endress, 1995; Remizowa et al., 2010).

Flowers are highly diverse in structure, form and sizeacross the eudicots. For example, the smallest eudicotflowers are those of Lepuropetalon, which are less than amillimetre in diameter. These are also the smallest flowersof any terrestrial angiosperm (only the flowers of someaquatic monocots are smaller); the largest flowers, up to1m in diameter, are those of Rafflesia, a parasitic memberof Malpighiales growing on the roots of vines.

Although most flowers are bisexual with fertile stamensand carpels in the same flower, there are several specieswhere one of the genders has become reduced or lost(Mitchell and Diggle, 2005). Unisexual flowers are con-centrated in the mainly wind-pollinated Rosid orders(Rosales and Fagales), often with male flowers grouped incatkins. Unisexual flowers have also evolved in animal-pollinated species, oftenwith a strongdimorphismbetweenmale and female flowers (e.g. Buxaceae and Euphorbia-ceae: Figure 2g; papaya in Caricaceae).

There is enormous variation in floral structure across theeudicots, including flowers with well-differentiated sepalsand petals, and others in which one or both whorls areabsent. Some clades, such as Santalales and Apiales have atendency for the sepalwhorl to become redundant,whereasin other clades petals are often absent (e.g. Caryophyllales:

Figure 3d; Saxifragales, Myrtales and Fagales). Further-more, floral parts can be free or fused. Sepals or petals maybe fused in a tube (Figure 3e and g), or are lifted on ahypanthium with the stamens (Figure 2c). This may lead tothe ovary becoming inferior. Fusion of stamens with petalsin a tube is very common and almost exclusively found inasterids (Figure 3f and Figure 4b).Stamen and carpel number can also vary considerably.

The number of stamens in eudicots, especially amongrosids, is often in two whorls, which appears to be theancestral condition (Figure 2d and Figure 3e), although onewhorl may be sterile (staminodial: Figure 4a) or absent.Polystemony has evolved secondarily in several rosids andbasal asterids where an initially low number of stamens ishighly increased (e.g. Malvaceae, Rosaceae, Hypericumand Capparis: Figure 2h). Stamen increase is generallylinked with a greater amount of pollen as reward for pol-linators. Carpels are the same in number as petals or fewer,rarely more, and they are generally fused in a compoundovary.Ovules are generally inserted in the centre of the fruit(axile placentation) or on the ovary wall (parietal pla-centation), and there is a strong tendency for reduction to asingle basal ovule in several clades, especially amongFabids (e.g. Rosales) and Campanulids (e.g. Asteraceae).There is also considerable variation in symmetry, with

both actinomorphy and zygomorphy frequently encoun-tered. In eudicots zygomorphy evolved several timesindependently from actinomorphic flowers, especially inthe asterid ordersDipsacales andLamiales,where it led to ahigh species diversification and specialised pollinationmechanisms. In the process stamens become often reducedto staminodes or are lost (Figure 4b; Walker-Larsen andHarder, 2000). Reversals to actinomorphic flowersoccurred frequently, either by fusion of dorsal petals or byoverexpression ofCYCLOIDEA genes in the ventral petals(Donoghue et al., 1998).Attraction of pollinators results from pigmentation in the

petals or hypanthiumand fromrewards in the formof pollenor nectar. Nectaries evolved in various ways in eudicots ondifferent parts of the flower. Among rosids, nectaries areeither separateglandson the receptacle or hypanthiumof theflower or on various floral organs (as in Geraniaceae orBrassicaceae; Figure 4a), or a central disc surrounding theovary (e.g. Rutaceae). Among asterids, disc nectaries arevery common (Lamiales and Solanales; Figure 4b) and theyshift to an epigynous position (when the ovary is inferior asin Asteraceae and Apiaceae) or in the lower part of theovary. All core Caryophyllales have nectaries within thestamens (Smets, 1986; Bernardello, 2007).Eudicots have evolved many mechanisms for the dis-

persal of seeds, which contributes highly to the diversity ofcrops (see below). Fruits are generally either capsular

Figure 3 Illustrations of flowers in Berberidopsidales, Caryophyllales and asterids. (a) Berberidopsis corallina (Berberidopsidaceae). Lateral view of

inflorescence with flowers and young fruits. (b) Delosperma lavisiae (Aizoaceae). Flower with many petaloid staminodes surrounding the stamens. (c) Lewisia

columbiana (Portulacaceae). Flower with petaloid sepals. (d) Minuartia sedoides (Caryophyllaceae). Apetalous flowers. (e) Kalmia latifolia (Ericaceae). Note

the fused petals and 10 stamens. (f) Diascia barberae (Scrophulariaceae). Lateral view of inflorescence; note spurs at the back of the petals. (g) Juanulloa

Mexicana (Solanaceae). Note the tubular flowers with coloured sepal tube.

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(releasing the seeds individually) or berries (releasing seedssimultaneously through ingestion). Seeds are either largeand rely on the presence of larger animals for dispersal (e.g.Sapindaceae and Fagaceae), or small and numerous (oftenin parasitic families of Gentianales and Lamiales). Espe-cially in Fagales different dispersal mechanisms evolved bythe fusion of bractswith reduced flowers (e.g. Juglandaceaeand Betulaceae), or by the association of several bracts andflowers into cupules containing nuts (e.g. Fagaceae: acornsand chestnuts). See also: Carpels; Coevolution: Plant–Insect; Evolution of Development; Flowering Plants,Evolution; Flowers; Fruit Structure and Diversity; Sepals;Stamens

Fossil History

Identification of fossil eudicots relies mainly on flowers,which represent characters with greater stability. Theeudicots can readily be identified in the fossil record bytheir three-grooved pollen. As a result, we have a goodunderstanding of the appearance of the eudicots, whichappears to be approximately 125 million years ago (Ma).Prominent early fossil eudicots include Platanaceae (planetrees and sycamores), Trochodendraceae andBuxaceae, allmembers of the early diverging eudicots. Following theorigin of the eudicots, the fossil record also suggests thatthis clade diversified rapidly, and by 90–80Ma many oftoday’s prominent families of angiosperms were estab-lished and are clearly recognisable in the fossil record (Friiset al., 2011). The fossil evidence suggesting a rapid radi-ation of eudicots after their initial diversification is inagreement with the phylogeny obtained using genesequence data (see above). The larger asterid and rosidclades emerged relatively late in the fossil record, and show

strong correlation with the diversification of pollinators.See also: Fossils in Phylogenetic Reconstruction; FossilRecord; Fossil Record: Quality

Biogeography and Ecology

Eudicots are extremely diverse in their biogeography andecology. Readers should consult entries on individualeudicot families. Eudicot species are found on every majorlandmass including Antarctica. They exhibit enormousecological diversity, occurring in diverse habitats includingtropical and temperate forests, alpine meadows, bogs,prairies, scrub, saltmarshes, anddeserts. Some eudicots arefully aquatic, including water milfoil (Myriophyllum;Haloragaceae) and bladderworts (Utricularia; Lentibular-iaceae). Several eudicots are well adapted to extremely dryhabitats, such as deserts. Well-known examples includecacti (Cactaceae) and euphorbs (Euphorbiaceae). Othereudicots survive extreme saline conditions (with too highconcentrations of salt in the soil for normal plants to sur-vive). Such plants are particularly common in Car-yophyllales, which often occur close to the sea. Examplesinclude Tamarix (Tamaricaceae), beetroot (Amar-anthaceae) and Limonium (Plumbaginaceae).The eudicots are diverse in habit, including annual and

perennial herbs, shrubs and large trees. They range fromthe smallest terrestrial angiosperm, plants approximately acentimetre in height (Lepuropetalon and Parnassiaceae), toEucalyptus trees (Myrtaceae) well over 100m.Eudicots also have the highest concentration of carniv-

orous (only one monocot) and parasitic genera or families.The carnivorous plant groups have evolved in parallel inseveral unrelated families, by developing sticky leaves(Drosera, Caryophyllales; Byblis, Lamiales), and pitcher

(a) (b)

Figure 4 Floral diagrams of representative species of rosids and asterids. (a) Actinomorphic flower of Brexia madagascariensis (Celastraceae). Note the two

stamen whorls of fertile stamens and laciniate glandular staminodes (grey ovals). (b) Zygomorphic flower of Penstemon fruticosus (Plantaginaceae). Note the

fusion of petals and stamens and the posterior staminode. Black arcs with triangles: bract and bracteoles; black arcs: sepals; white arcs: petals; ovaries shown

with ovules; grey: nectariferous tissue. Reproduced from Ronse De Craene (2010).

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plants (Sarracenia, Ericales; Nepenthes, Caryophyllales;and Cephalotus, Oxalidales). Several eudicots are hemi-parasites, that is, they are photosynthetic during at leastone phase of their life cycle and derive mainly water anddissolved minerals from their hosts. Most members ofSantalales such as the mistletoes (Viscum, Viscaceae) orsandalwood (Santalaceae) are hemiparasites. Holopar-asites, in contrast, represent the most extreme manifest-ation of the parasiticmode in that they lack photosynthesisand depend on their hosts for water as well as for inorganicand organic nutrients. Orobanchaceae are an importantgroup with either hemiparasites or nonphotosyntheticholoparasites in Lamiales, and genera such as Striga cancause serious damage to crops.

The high diversity in core eudicots is linked with therange of pollination systems and life histories. Trends toabiotic (wind-) and biotic (mainly insect-) pollination wenthand in hand either with increased reduction (as in Gun-nera: Figure 2b) or complexity (a strong adaptation offlowers to specific pollinators by developing zygomorphy,long tubes, etc.: Figure 2e and f and Figure 3f and g).Reductive trends to abiotic pollination were occasionallyreversed in evolution, and flowers used up remainingresources in attracting pollinators (e.g. Euphorbia indeveloping pseudoflowerswith coloured bracts, glands andreduced flowers: Figure 2g, Asteraceae with small flowersgrouped in heads mimicking flowers; Aizoaceae withcoloured outer staminodes formed with polystemony:Figure 3b). See also: Biogeographical Regions; History ofBiogeography; Carnivorous Plants; Hot Deserts; Parasit-ism: the Variety of Parasites, Pollination by Animals

Economic Importance: Crops andOrnamentals

Outside of the grasses such as wheat, corn and rice (all inthemonocot family Poaceae), the vastmajority of plants ofeconomic importance are members of the large eudicotclade.Again, somany eudicots are of economic importanceeither as crops, timber or ornamentals, that it is not pos-sible to list them all here. The eudicots contain a highproportion of our leaf vegetables, fruits, spices and nuts:Myrtaceae (allspice, cloves and guava), Anacardiaceae(mango and cashew), Rutaceae (oranges and limes),Apiaceae (coriander, fennel and carrots) and Amar-anthaceae (spinach, beetroot, amaranth and quinoa).Examples of important eudicot families of great economicimportance (see also Table 1) include members of the beanor legume family (Fabaceae), such as soya bean, lentils,alfalfa and green beans; the sunflower family (Asteraceae),which includes sunflower, lettuce and artichokes; and thecotton family (Malvaceae) which provides cotton, and isalso the source of chocolate (Theobroma cacao). Mustardoil is found in all Brassicales, and has been economicallysourced in Capparaceae (caper family) and Brassicaceae(mustard family: cabbage, kale, broccoli, cauliflower,

mustard and horse radish). The rose family (Rosaceae)provides not only fruits such as strawberries, raspberries,apples, cherries, peaches, plums and almonds, but alsonumerous ornamentals. The Solanaceae is the source oftobacco, tomatoes, chilies and potatoes. Our mostimportant beverages are all eudicots, such as coffee(Rubiaceae), tea (Theaceae), wine (Vitaceae) and eveningredients of Coke (Cola, Malvaceae) and beer (Hop,Cannabaceae). Eudicots contain the most importantdrugs, such as opium (Papaver somniferum, Papaveraceae),or quinine (Cinchona, Rubiaceae). Important timber spe-cies besides conifers are also mainly from eudicots, espe-cially Fagaceae (oak and beech), Lamiaceae (teak),Dipterocarpaceae (Shorea) and Burseraceae (cedar andmahogany).Most of our familiar horticultural plants are eudicots;

this includes a diverse array of trees, shrubs and annual andperennial herbs. The sheer number of horticultural plantsin the eudicot clade permits only a brief overview here (seeTable 1). Other horticulturally important eudicot speciesinclude members of the Geraniaceae (Pelargonium),Lamiaceae (rosemary, Salvia), Primulaceae (primroses),Begoniaceae (Begonia), Cornaceae (dogwood), Ericaceae(Rhododendron, heath), numerous species of cacti (Cacta-ceae), numerous members of the Asteraceae (includingsunflower, asters, Chrysanthemum, Dahlia, Liatrisand marigolds), Adoxaceae (Viburnum), Caprifoliaceae(Lonicera, Scabiosa), Hydrangeaceae (Hydrangea, Phila-delphus), numerous representatives of Ranunculaceae(including columbine, buttercups, larkspur and monks-hood) and Papaveraceae (Papaver, Corydalis) and somemembers of the Solanaceae, such as Petunia. See also:Asterales (Sunflower); Brassicaceae (Mustard Family);Cornales (Dogwood); Cucurbitaceae (Vine Crops); Eri-cales (Rhododendron); Geraniales (Geranium); Malvales(Mallow); Poales (Grasses); Rosales (Rose); Solanumlycopersicum (Tomato)

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Further Reading

Judd WS, Campbell CS, Kellogg EA, Stevens PF and Donoghue

MJ (2002) Plant Systematics: A Phylogenetic Approach. Sun-

derland, MA: Sinauer Associates.

Simpson MG (2010) Plant Systematics, 2nd edn. Amsterdam:

Elsevier.

Stevens PF (2001 onwards). Angiosperm Phylogeny Website.

Version 9, June 2008 (and more or less continuously updated

since). http://www.mobot.org/MOBOT/research/APweb/

Eudicots

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