Eudicots

The eudicots, Eudicotidae or eudicotyledons are a clade of flowering plants that had been called tricolpates or non-magnoliid dicots by previous authors. The 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.[1] 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[2]. 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. 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.

The other 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.[3]

Numerous familiar plants are eudicots, including many common food plants, trees, and ornamentals. Some common and familiar eudicots include members of the sunflower family such as the common dandelion, the forget-me-not, cabbage and other members of its family, apple, buttercup, maple, and macadamia. Most leafy trees of midlatitudes also belong to eudicots, with notable exceptions being magnolias and tulip trees which belong to magnoliids, and Ginkgo biloba, which is not an angiosperm.

The name "eudicots" (plural) is used in the APG system, of 1998, and APG II system, of 2003, for classification of angiosperms. It is applied to a clade, a monophyletic group, which includes most of the (former) dicots.

"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.[4][3]

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.[5]

Eudicots
Temporal range: Early Cretaceous - recent
Primulas aka
Primula hortensis, an eudicot
Scientific classification
Kingdom: Plantae
Clade: Angiosperms
Clade: Eudicots
Clades (APG IV)
Arabis voch1-4
Arabis pollen has three colpi.

Subdivisions

The eudicots can be divided into two groups: the basal eudicots and the core eudicots.[6] Basal eudicot is an informal name for a paraphyletic group. The core eudicots are a monophyletic group.[7] 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.[8]

The Pentapetalae can be then divided into three clades:

This division of the eudicots is shown in the following cladogram:[9]

eudicots
basal eudicots

(paraphyletic group: Ranunculales, Proteales, Trochodendrales, Buxales)

core eudicots

Gunnerales

Pentapetalae

Dilleniales

superrosids

Saxifragales

rosids

Vitales

eurosids

fabids

malvids

superasterids

Santalales

Berberidopsidales

Caryophyllales

asterids

Cornales

Ericales

euasterids

campanulids

lamiids

The following is a more detailed breakdown according to APG IV, showing within each clade and orders:[10]

References

  1. ^ Endress, Peter K. (2002). "Morphology and Angiosperm Systematics in the Molecular Era" (PDF). Botanical Review. Structural Botany in Systematics: A Symposium in Memory of William C. Dickison. 68 (4): 545–570. doi:10.1663/0006-8101(2002)068[0545:maasit]2.0.co;2. JSTOR 4354438.
  2. ^ Coiro, Mario; Doyle, James A.; Hilton, Jason (2019-01-25). "How deep is the conflict between molecular and fossil evidence on the age of angiosperms?". New Phytologist. doi:10.1111/nph.15708. PMID 30681148.
  3. ^ a b Judd & Olmstead 2004
  4. ^ Sporne, Kenneth R. (1972). "Some Observations on the Evolution of Pollen Types in Dicotyledons". New Phytologist. 71 (1): 181–5. doi:10.1111/j.1469-8137.1972.tb04826.x.
  5. ^ "Archived copy". Archived from the original on 2009-02-03. Retrieved 2009-02-16.CS1 maint: Archived copy as title (link)
  6. ^ Worberg, A; Quandt, D; Barniske, A-M; Löhne, C; Hilu, KW; Borsch, T (2007). "Phylogeny of basal eudicots: insights from non-coding and rapidly evolving DNA". Organisms, Diversity and Evolution. 7 (1): 55–77. doi:10.1016/j.ode.2006.08.001.
  7. ^ Soltis, Douglas E.; Soltis, Pamela S.; Endress, Peter K.; Chase, Mark W. (2005). Phylogeny and Evolution of Angiosperms. Sunderland, MA: Sinauer Associates. ISBN 9780878938179.
  8. ^ Moore, Michael J.; Soltis, Pamela S.; Bell, Charles D.; Burleigh, J. Gordon & Soltis, Douglas E. (2010). "Phylogenetic analysis of 83 plastid genes further resolves the early diversification of eudicots". Proceedings of the National Academy of Sciences. 107 (10): 4623–8. Bibcode:2010PNAS..107.4623M. doi:10.1073/pnas.0907801107. PMC 2842043. PMID 20176954.
  9. ^ Based on:
    Stevens, P.F. (2001–2014). "Trees". Angiosperm Phylogeny Website. Retrieved 2014-11-17.
    Stevens, P.F. (2001–2016). "Eudicots". Angiosperm Phylogeny Website. Retrieved 2014-11-17.
  10. ^ Angiosperm Phylogeny Group (2016). "An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG IV". Botanical Journal of the Linnean Society. 181 (1): 1–20. doi:10.1111/boj.12385.

Bibliography

External links

APG III system

The APG III system of flowering plant classification is the third version of a modern, mostly molecular-based, system of plant taxonomy being developed by the Angiosperm Phylogeny Group (APG). Published in 2009, it was superseded in 2016 by a further revision, the APG IV system.Along with the publication outlining the new system, there were two accompanying publications in the same issue of the Botanical Journal of the Linnean Society. The first, by Chase & Reveal, was a formal phylogenetic classification of all land plants (embryophytes), compatible with the APG III classification. As the APG have chosen to eschew ranks above order, this paper was meant to fit the system into the existing Linnaean hierarchy for those that prefer such a classification. The result was that all land plants were placed in the class Equisetopsida, which was then divided into 16 subclasses and a multitude of superorders. The second, by Haston et al., was a linear sequence of families following the APG III system (LAPG III).

This provided a numbered list to the 413 families of APG III. A linear sequence is of particular use to herbarium curators and those working on floristic works wishing to arrange their taxa according to APG III.

APG IV system

The APG IV system of flowering plant classification is the fourth version of a modern, mostly molecular-based, system of plant taxonomy for flowering plants (angiosperms) being developed by the Angiosperm Phylogeny Group (APG). It was published in 2016, seven years after its predecessor the APG III system was published in 2009, and 18 years after the first APG system was published in 1998. In 2009, a linear arrangement of the system was published separately; the APG IV paper includes such an arrangement, cross-referenced to the 2009 one.Compared to the APG III system, the APG IV system recognizes five new orders (Boraginales, Dilleniales, Icacinales, Metteniusales and Vahliales), along with some new families, making a total of 64 angiosperm orders and 416 families. In general, the authors describe their philosophy as "conservative", based on making changes from APG III only where "a well-supported need" has been demonstrated. This has sometimes resulted in placements that are not compatible with published studies, but where further research is needed before the classification can be changed.

Apiales

The Apiales are an order of flowering plants. The families are those recognized in the APG III system. This is typical of the newer classifications, though there is some slight variation and in particular, the Torriceliaceae may be divided.Under this definition, well-known members include carrots, celery, parsley, and Hedera helix (English ivy).

The order Apiales is placed within the asterid group of eudicots as circumscribed by the APG III system. Within the asterids, Apiales belongs to an unranked group called the campanulids, and within the campanulids, it belongs to a clade known in phylogenetic nomenclature as Apiidae. In 2010, a subclade of Apiidae named Dipsapiidae was defined to consist of the three orders: Apiales, Paracryphiales, and Dipsacales.

Basal (phylogenetics)

In phylogenetics, basal is the direction of the base (or root) of a rooted phylogenetic tree or cladogram. The term may be more strictly applied only to nodes adjacent to the root, or more loosely applied to nodes regarded as being close to the root. Each node in the tree corresponds to a clade; i.e., clade C may be described as basal within a larger clade D if its root is directly linked to the root of D. The terms deep-branching or early-branching are similar in meaning.

While there must always be two or more equally basal clades sprouting from the root of every cladogram, those clades may differ widely in taxonomic rank and/or species diversity. If C is a basal clade within D that has the lowest rank of all basal clades within D, C may be described as the basal taxon of that rank within D. Greater diversification may be associated with more evolutionary innovation, but ancestral characters should not be imputed to the members of a less species-rich basal clade without additional evidence, as there can be no assurance such an assumption is valid.In general, clade A is more basal than clade B if B is a subgroup of the sister group of A. Within large groups, "basal" may be used loosely to mean 'closer to the root than the great majority of', and in this context terminology such as "very basal" may arise. A 'core clade' is a clade representing all but the basal clade(s) of lowest rank within a larger clade; e.g., core eudicots.

Dicotyledon

The dicotyledons, also known as dicots (or more rarely dicotyls), are one of the two groups into which all the flowering plants or angiosperms were formerly divided. The name refers to one of the typical characteristics of the group, namely that the seed has two embryonic leaves or cotyledons. There are around 200,000 species within this group. The other group of flowering plants were called monocotyledons or monocots, typically having one cotyledon. Historically, these two groups formed the two divisions of the flowering plants.

Largely from the 1990s onwards, molecular phylogenetic research confirmed what had already been suspected, namely that dicotyledons are not a group made up of all the descendants of a common ancestor (i.e. they are not a monophyletic group). Rather, a number of lineages, such as the magnoliids and groups now collectively known as the basal angiosperms, diverged earlier than the monocots did. The traditional dicots are thus a paraphyletic group. The largest clade of the dicotyledons are known as the eudicots. They are distinguished from all other flowering plants by the structure of their pollen. Other dicotyledons and monocotyledons have monosulcate pollen, or forms derived from it, whereas eudicots have tricolpate pollen, or derived forms, the pollen having three or more pores set in furrows called colpi.

Fabales

The Fabales are an order of flowering plants included in the rosid group of the eudicots in the Angiosperm Phylogeny Group II classification system. In the APG II circumscription, this order includes the families Fabaceae or legumes (including the subfamilies Caesalpinioideae, Mimosoideae, and Faboideae), Quillajaceae, Polygalaceae or milkworts (including the families Diclidantheraceae, Moutabeaceae, and Xanthophyllaceae), and Surianaceae. Under the Cronquist system and some other plant classification systems, the order Fabales contains only the family Fabaceae. In the classification system of Dahlgren the Fabales were in the superorder Fabiflorae (also called Fabanae) with three familiese corresponding to the subfamilies of Fabaceae in APG II. The other families treated in the Fabales by the APG II classification were placed in separate orders by Cronquist, the Polygalaceae within its own order, the Polygalales, and the Quillajaceae and Surianaceae within the Rosales.The Fabaceae, as the third-largest plant family in the world, contain most of the diversity of the Fabales, the other families making up a comparatively small portion of the order's diversity. Research in the order is largely focused on the Fabaceae, due in part to its great biological diversity, and to its importance as food plants. The Polygalaceae are fairly well researched among plant families, in part due to the large diversity of the genus Polygala, and other members of the family being food plants for various Lepidoptera (butterfly and moth) species. While taxonomists using molecular phylogenetic techniques find strong support for the order, questions remain about the morphological relationships of the Quillajaceae and Surianaceae to the rest of the order, due in part to limited research on these families.

Flowering plant

The flowering plants, also known as angiosperms, Angiospermae or Magnoliophyta, are the most diverse group of land plants, with 416 families, approximately 13,164 known genera and c. 369,000 known species. Like gymnosperms, angiosperms are seed-producing plants. However, they are distinguished from gymnosperms by characteristics including flowers, endosperm within the seeds, and the production of fruits that contain the seeds. Etymologically, angiosperm means a plant that produces seeds within an enclosure; in other words, a fruiting plant. The term comes from the Greek words angeion ("case" or "casing") and sperma ("seed").

The ancestors of flowering plants diverged from gymnosperms in the Triassic Period, 245 to 202 million years ago (mya), and the first flowering plants are known from 160 mya. They diversified extensively during the Early Cretaceous, became widespread by 120 mya, and replaced conifers as the dominant trees from 100 to 60 mya.

Gentianales

Gentianales is an order of flowering plants, included within the asterid clade of eudicots. It comprises more than 16,000 species in about 1,138 genera in 5 families. More than 80% of the species in this order belong to the Rubiaceae family.

Malvales

The Malvales are an order of flowering plants. As circumscribed by APG II-system, the order includes about 6000 species within 9 families. The order is placed in the eurosids II, which are part of the eudicots.

The plants are mostly shrubs and trees; most of its families have a cosmopolitan distribution in the tropics and subtropics, with limited expansion into temperate regions. An interesting distribution occurs in Madagascar, where three endemic families of Malvales (Sphaerosepalaceae, Sarcolaenaceae and Diegodendraceae) occur.

Many species of Malvaceae sensu lato are known for their wood, with that of Ochroma (balsa) being known for its lightness, and that of Tilia (lime, linden, or basswood) as a popular wood for carving. Fruit of the cacao tree (Theobroma cacao) are used as an ingredient for chocolate. Kola nuts (genus Cola) are notable for their high content of caffeine and, in past, were commonly used for preparing of various cola drinks. Other well-known members of Malvales in the APG II sense are daphnes, hibiscus, hollyhocks, okra, baobab trees, cotton, and kapok.

Oxalidales

The Oxalidales is an order of flowering plants, included within the rosid subgroup of eudicots. Compound leaves are common in Oxalidales and the majority of the species in this order have five or six sepals and petals. The following families are typically placed here:

Family Brunelliaceae

Family Cephalotaceae (Cephalotus follicularis)

Family Connaraceae

Family Cunoniaceae

Family Elaeocarpaceae

Family Huaceae

Family Oxalidaceae (wood sorrel family)The Cephalotaceae family contains a single species, a pitcher plant found in Southwest Australia.

Under the Cronquist system, most of the above families were placed in the Rosales. The Oxalidaceae were placed in the Geraniales, and the Elaeocarpaceae split between the Malvales and Polygalales, in the latter case being treated as the Tremandraceae.

Persoonia longifolia

Persoonia longifolia, the upright snottygobble, also known as the long-leaf persoonia or just snottygobble, is a species of tall shrub or small tree in the plant genus Persoonia, reaching 1 to 5 metres (3–17 ft) in height. It is found in the Jarrah forests of southwest Western Australia. This species is characterised by its long narrow dark green leaves, dark yellow to orange flowers and distinctive flaky dark red bark.

Persoonia micranthera

Persoonia micranthera, commonly known as the small-flowered snottygobble, is an endangered prostrate shrub with yellow flowers and thin bark. It grows only on two peaks, Bluff Knoll and Isongerup Peak, in the eastern section of the Stirling Range, Western Australia. A slow-growing plant, it takes more than six years to produce flowers and seed.

Prior to 1980, Persoonia micranthera was also present on Coyanerup Peak, but none were found there in 1990, and that population is now believed extinct. In April 1991 an intense bushfire burnt all known populations except for three adult plants on Isongerup Peak. A 1997 survey noted three adults and 150 seedlings on Isongerup Peak, but a 1999 survey of Bluff Knoll found no adults and only two seedlings there.

Proteales

Proteales is the botanical name of an order of flowering plants consisting of two (or three) families. The Proteales have been recognized by almost all taxonomists.

Ranunculales

Ranunculales is an order of flowering plants. Of necessity it contains the family Ranunculaceae, the buttercup family, because the name of the order is based on the name of a genus in that family. Ranunculales belongs to a paraphyletic group known as the basal eudicots. It is the most basal clade in this group; in other words, it is sister to the remaining eudicots. Widely known members include poppies, barberries, and buttercups.

Rosids

The rosids are members of a large clade (monophyletic group) of flowering plants, containing about 70,000 species, more than a quarter of all angiosperms.The clade is divided into 16 to 20 orders, depending upon circumscription and classification. These orders, in turn, together comprise about 140 families.Fossil rosids are known from the Cretaceous period. Molecular clock estimates indicate that the rosids originated in the Aptian or Albian stages of the Cretaceous, between 125 and 99.6 million years ago.

Sapindales

Sapindales is an order of flowering plants. Well-known members of Sapindales include citrus; maples, horse-chestnuts, lychees and rambutans; mangos and cashews; frankincense and myrrh; mahogany and neem.

The APG III system of 2009 includes it in the clade malvids (in rosids, in eudicots) with the following nine families:

Anacardiaceae

Biebersteiniaceae

Burseraceae

Kirkiaceae

Meliaceae

Nitrariaceae (including Peganaceae and Tetradiclidaceae)

Rutaceae

Sapindaceae

SimaroubaceaeThe APG II system of 2003 allowed the optional segregation of families now included in the Nitrariaceae.

In the classification system of Dahlgren the Rutaceae were placed in the order Rutales, in the superorder Rutiflorae (also called Rutanae). The Cronquist system of 1981 used a somewhat different circumscription, including the following families:

Staphyleaceae

Melianthaceae

Bretschneideraceae

Akaniaceae

Sapindaceae

Hippocastanaceae

Aceraceae

Burseraceae

Anacardiaceae

Julianiaceae

Simaroubaceae

Cneoraceae

Meliaceae

Rutaceae

ZygophyllaceaeThe difference from the APG III system is not as large as may appear, as the plants in the families Aceraceae and Hippocastanaceae stay in this order at APG III (both included in family Sapindaceae). The species now composing the family Nitrariaceae in APG III also belonged to this order in the Cronquist system as part of the family Zygophyllaceae, while those now in the family Kirkiaceae were present as part of the family Simaroubaceae.

Saxifragales

The Saxifragales are an order of flowering plants. Their closest relatives are a large eudicot group known as the rosids by the definition of rosids given in the APG II classification system. Some authors define the rosids more widely, including Saxifragales as their most basal group. Saxifragales is one of the eight groups that compose the core eudicots. The others are Gunnerales, Dilleniaceae, Rosids, Santalales, Berberidopsidales, Caryophyllales, and Asterids.Saxifragales have an extensive fossil record. The extant members are apparently remnants of a formerly diverse and widespread order.The Saxifragales order, as it is now understood, is based upon the results of molecular phylogenetic studies of DNA sequences. It is not part of any of the classification systems based on plant morphology. The group is much in need of comparative anatomical study, especially in light of the recent expansion of the family Peridiscaceae to include Medusandra, a genus that before 2009 had usually not been placed in Saxifragales.The order is divided into suprafamilial groups as shown on the phylogenetic tree below. These groups are informal and are not understood to have any particular taxonomic rank.

Superasterids

The superasterids are members of a large clade (monophyletic group) of flowering plants, containing more than 122,000 species.

The clade is divided into 20 orders as defined in APG IV system. These orders, in turn, together comprise about 146 families.The name is based upon the name "Asteridae", which had usually been understood to be a subclass.

Superrosids

The superrosids are members of a large clade (monophyletic group) of flowering plants, containing more than 88,000 species, more than a quarter of all angiosperms.The clade is divided into 18 orders as defined in APG IV system. These orders, in turn, together comprise about 155 families.The name is based upon the name "Rosidae", which had usually been understood to be a subclass.

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