Eudicots

Abstract

Eudicots represent the largest clade of flowering plants, comprising approximately 75% of all species and characterised by pollen having three apertures. Eudicots consist of a basal grade and a large (core eudicot) clade, which comprises the majority of species. Evolution of flowers in core eudicots is highly diverse and is driven by repeated diversifications 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 group of plants, occupying almost all habitats on earth. Apart from Poaceae in the monocots, the major food crops are found in the core eudicots. Flowers of eudicots are 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 zygomorphic flowers (Leguminosae and Lamiales) or wind‐pollinated apetalous flowers (Fagales and Caryophyllales). Dispersal mechanisms are also highly diverse.

Key Concepts:

  • Eudicots contain the highest concentration of economic plants outside the grasses.

  • Molecular phylogenies have almost resolved the relationships within eudicots.

  • Eudicots occupy almost all habitats on earth and range from the smallest to the largest flowering plants.

  • Eudicots represent the most successful plant group with the highest number of species in the flowering plants.

  • Eudicots are composed of a basal grade of early diverging eudicots and a clade of core eudicots.

  • Petals have evolved several times from stamens or from bracts.

  • The origin of the core eudicot flower remains controversial.

  • Floral evolution in eudicots is mainly dependent on diversity of pollination systems.

  • Flowers of core eudicots have undergone opposing trends of reduction and increased complexity.

  • The distinction dicot–monocot should be abandoned, as it does not represent a natural division.

Keywords: angiosperms; asterids; core eudicots; flower evolution; flowering plants; phylogeny; pollination; rosids

Figure 1.

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

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.

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.

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 .

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Further Reading

Judd WS, Campbell CS, Kellogg EA, Stevens PF and Donoghue MJ (2002) Plant Systematics: A Phylogenetic Approach. Sunderland, 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/

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How to Cite close
Ronse De Craene, Louis P(May 2012) Eudicots. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0003684.pub2]