Eudicots

The eudicots or eudicotyledons are flowering plants that have two seed leaves (cotyledons) upon germination. The term derives from dicotyledon (etymologically, eu = true; di = two; cotyledon = seed leaf). Historically, authors have used the terms tricolpates or non-magnoliid dicots. The current botanical terms were introduced in 1991, by evolutionary botanist James A. Doyle and paleobotanist Carol L. Hotton, to emphasize the later evolutionary divergence of tricolpate dicots from earlier, less specialized, dicots.

Eudicots Temporal range: Early Cretaceous - recent PreꞒ Ꞓ O S D C P T J K Pg N
Two seed leaves during germination (Brassica sp.)
Scientific classification
Kingdom:	Plantae
Clade:	Embryophytes
Clade:	Polysporangiophytes
Clade:	Tracheophytes
Clade:	Spermatophytes
Clade:	Angiosperms
Clade:	Eudicots
Clades (APG IV)
Basal eudicots: Buxales Proteales Ranunculales Trochodendrales Core eudicots: Clades Superasterids Superrosids Orders Dilleniales Gunnerales

Arabis pollen has three colpi.

Scores of familiar plants are eudicots, including many commonly cultivated and edible plants, numerous trees, tropicals and ornamentals. Among the most well-known eudicot genera are those of the sunflower (Helianthus), dandelion (Taraxacum), forget-me-not (Myosotis), cabbage (Brassica), apple (Malus), buttercup (Ranunculus), maple (Acer) and macadamia (Macadamia). Most leafy, mid-latitude trees are also classified as eudicots, with notable exceptions being the magnolias and American tulip tree (Liriodendron)—which belong to the magnoliids.

Description

The close relationships among flowering plants with tricolpate pollen grains was initially seen in morphological studies of shared derived characters. These plants have a distinct trait in their pollen grains of exhibiting three colpi or grooves paralleling the polar axis.

Later molecular evidence confirmed the genetic basis for the evolutionary relationships among flowering plants with tricolpate pollen grains and dicotyledonous traits. The term means "true dicotyledons", as it contains the majority of plants that have been considered dicots and have characteristics of the dicots. One of the genetic traits which defines the eudicots is the duplication of DELLA protein-encoding genes in their most recent common ancestor. The term "eudicots" has subsequently been widely adopted in botany to refer to one of the two largest clades of angiosperms (constituting over 70% of the angiosperm species), monocots being the other. The remaining angiosperms include magnoliids and what are sometimes referred to as basal angiosperms or paleodicots, but these terms have not been widely or consistently adopted, as they do not refer to a monophyletic group.^{[citation needed]}

According to molecular clock calculations, the lineage that led to eudicots split from other plants about 134 million years ago or 155–160 million years ago. Fossil records suggested that basal eudicots were already diverse around 121 million years ago.

Taxonomy

The earlier name for the eudicots is tricolpates, a name which refers to the grooved structure of the pollen. Members of the group have tricolpate pollen, or forms derived from it. These pollens have three or more pores set in furrows called colpi. In contrast, most of the other seed plants (that is the gymnosperms, the monocots and the paleodicots) produce monosulcate pollen, with a single pore set in a differently oriented groove called the sulcus. The name "tricolpates" is preferred by some botanists to avoid confusion with the dicots, a nonmonophyletic group.

The name "eudicots" (plural) is used in the APG systems (from APG system, of 1998, to APG IV system, of 2016) for classification of angiosperms. It is applied to a clade, a monophyletic group, which includes most of the (former) dicots.^{[citation needed]}

"Tricolpate" is a synonym for the "Eudicot" monophyletic group, the "true dicotyledons" (which are distinguished from all other flowering plants by their tricolpate pollen structure). The number of pollen grain furrows or pores helps classify the flowering plants, with eudicots having three colpi (tricolpate), and other groups having one sulcus.

Pollen apertures are any modification of the wall of the pollen grain. These modifications include thinning, ridges and pores, they serve as an exit for the pollen contents and allow shrinking and swelling of the grain caused by changes in moisture content. The elongated apertures/ furrows in the pollen grain are called colpi (singular colpus), which, along with pores, are a chief criterion for identifying the pollen classes.

Subdivisions

The eudicots can be divided into two groups: the basal eudicots and the core eudicots. Basal eudicot is an informal name for a paraphyletic group. The core eudicots are a monophyletic group. A 2010 study suggested the core eudicots can be divided into two clades, Gunnerales and a clade called Pentapetalae, comprising all the remaining core eudicots.

The Pentapetalae can be then divided into three clades:^{[citation needed]}

• Dilleniales
• superrosids consisting of Saxifragales and rosids (the APG IV system includes the Vitales in the rosids)
• superasterids consisting of Santalales, Berberidopsidales, Caryophyllales and asterids

This division of the eudicots is shown in the following cladogram:

eudicots	basal eudicots (paraphyletic group: Ranunculales, Proteales, Trochodendrales, Buxales) core eudicots Gunnerales Pentapetalae Dilleniales superrosids Saxifragales rosids Vitales eurosids fabids (8 orders) malvids (8 orders) superasterids Santalales Berberidopsidales Caryophyllales asterids Cornales Ericales euasterids campanulids (7 orders) lamiids (8 orders)

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The following is a more detailed breakdown according to APG IV, showing within each clade and orders:

• clade Eudicots

  order Ranunculales

  order Proteales

  order Trochodendrales

  order Buxales

  clade Core eudicots

  order Gunnerales

  order Dilleniales

  clade Superrosids

  order Saxifragales

  clade Rosids

  order Vitales

  clade Fabids

  order Fabales

  order Rosales

  order Fagales

  order Cucurbitales

  order Oxalidales

  order Malpighiales

  order Celastrales

  order Zygophyllales

  clade Malvids

  order Geraniales

  order Myrtales

  order Crossosomatales

  order Picramniales

  order Malvales

  order Brassicales

  order Huerteales

  order Sapindales

  clade Superasterids

  order Berberidopsidales

  order Santalales

  order Caryophyllales

  clade Asterids

  order Cornales

  order Ericales

  clade Campanulids

  order Aquifoliales

  order Asterales

  order Escalloniales

  order Bruniales

  order Apiales

  order Dipsacales

  order Paracryphiales

  clade Lamiids

  order Solanales

  order Lamiales

  order Vahliales

  order Gentianales

  order Boraginales

  order Garryales

  order Metteniusales

  order Icacinales