Asteridae
Encyclopedia
Asteridae is a clade
of plants, known for their flowers. Asteridae has been ranked as a subclass, but this ranking has varied depending on the taxonomy
being used. Composition of the clade has also varied, however, by definition it always includes the family Asteraceae
(Compositae).
One of the better-known and more influential systems that formally recognized subclass Asteridae was the Cronquist system
devised by botanist Arthur Cronquist
, which included the orders:
Most of the above orders as defined by Cronquist have been dramatically redefined on the basis of recent molecular systematic studies.
To a large extent Cronquist's subclass Asteridae corresponds with the older concepts of Sympetalae and Tubiflorae, groups that were defined by having their petals united into a tube. However, these older classifications contained some sympetalous families, such as Cucurbitaceae
, that are now known not to be closely related. Cronquist's concept also corresponds closely with the APG II group of euasterids but the APG does not formally recognize a group called "Asteridae" (or any other group above the rank of order).
Recent phylogenetic studies have suggested that several families, including three major orders not included in Asteridae by Cronquist, Ericales
, Cornales
, and Apiales
, also belong to the asterid group. The circumscription of subclass Asteridae, as well as the circumscriptions of the orders contained within it, is currently in a state of flux; many systematic botanists refer to these as clades (asterids
, euasterids, etc.), rather than use formal names such as subclass Asteridae.
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
of plants, known for their flowers. Asteridae has been ranked as a subclass, but this ranking has varied depending on the taxonomy
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...
being used. Composition of the clade has also varied, however, by definition it always includes the family Asteraceae
Asteraceae
The Asteraceae or Compositae , is an exceedingly large and widespread family of vascular plants. The group has more than 22,750 currently accepted species, spread across 1620 genera and 12 subfamilies...
(Compositae).
One of the better-known and more influential systems that formally recognized subclass Asteridae was the Cronquist system
Cronquist system
The Cronquist system is a taxonomic classification system of flowering plants. It was developed by Arthur Cronquist in his texts An Integrated System of Classification of Flowering Plants and The Evolution and Classification of Flowering Plants .Cronquist's system places flowering plants into two...
devised by botanist Arthur Cronquist
Arthur Cronquist
Arthur John Cronquist was a North American botanist and a specialist on Compositae. He is considered one of the most influential botanists of the 20th century, largely due to his formulation of the Cronquist system. Two plant genera in the aster family have been named in his honor...
, which included the orders:
- GentianalesGentianalesGentianales are an order of flowering plants, included within the asterid group of dicotyledons.The circumscription of Gentiales in the Cronquist system included a broadly defined Loganiaceae , Retziaceae, Gentianaceae, Saccifoliaceae, Apocynaceae, and Asclepiadaceae...
- SolanalesSolanalesThe Solanales are an order of flowering plants, included in the asterid group of dicotyledons. Some older sources used the name Polemoniales for this order....
- LamialesLamialesLamiales is an order in the asterid group of dicotyledonous flowering plants. It includes approximately 11,000 species divided into about 20 families...
- CallitrichalesCallitrichalesCallitrichales Dumort is an order of flowering plants. As circumscribed by American botanist Arthur Cronquist in the Cronquist system , the order included three families:* Hippuridaceae* Callitrichaceae* Hydrostachyaceae....
- Plantaginales
- Scrophulariales
- CampanulalesCampanulalesCampanulales is a valid botanic name for a plant order. It was used in the Cronquist system as an order within the subclass Asteridae in the class Magnoliopsida flowering plants...
- RubialesRubialesRubiales was an order of flowering plants in the Cronquist system, including the families Rubiaceae and Theligonaceae. The latest APG system does not recognize this order and places the families within Gentianales....
- DipsacalesDipsacalesThe Dipsacales are an order of flowering plants, included within the asterid group of dicotyledons.Under the Cronquist system, the order included Adoxaceae, Caprifoliaceae, Dipsacaceae, and Valerianaceae. Under the more recent Angiosperm Phylogeny Group system, the circumscription of the order is...
- CalyceralesCalyceralesThe Calycerales is a valid botanic name for an order of flowering plants. When accepted, it included the Acicarpha and the Calycera. These are now placed in the Asterales, and Calycerales treated as a synonym of Asterales....
- AsteralesAsteralesAsterales is an order of dicotyledonous flowering plants that includes the composite family and its related families.The order is a cosmopolite, and includes mostly herbaceous species, although a small number of trees and shrubs are also present.The Asterales can be characterized on the...
Most of the above orders as defined by Cronquist have been dramatically redefined on the basis of recent molecular systematic studies.
To a large extent Cronquist's subclass Asteridae corresponds with the older concepts of Sympetalae and Tubiflorae, groups that were defined by having their petals united into a tube. However, these older classifications contained some sympetalous families, such as Cucurbitaceae
Cucurbitaceae
The plant family Cucurbitaceae consists of various squashes, melons, and gourds, including crops such as cucumber, pumpkins, luffas, and watermelons...
, that are now known not to be closely related. Cronquist's concept also corresponds closely with the APG II group of euasterids but the APG does not formally recognize a group called "Asteridae" (or any other group above the rank of order).
Recent phylogenetic studies have suggested that several families, including three major orders not included in Asteridae by Cronquist, Ericales
Ericales
The Ericales are a large and diverse order of dicotyledons, including for example tea, persimmon, blueberry, Brazil nut, and azalea. The order includes trees and bushes, lianas and herbaceous plants. Together with ordinary autophytic plants, the Ericales include chlorophyll-deficient...
, Cornales
Cornales
Cornales is an order of flowering plants, basal among the asterids, containing about 600 species. Plants within Cornales usually have four-parted flowers, drupaceous fruits, and inferior gynoecia topped with disc-shaped nectaries...
, and Apiales
Apiales
The Apiales are an order of flowering plants. The families given at right 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...
, also belong to the asterid group. The circumscription of subclass Asteridae, as well as the circumscriptions of the orders contained within it, is currently in a state of flux; many systematic botanists refer to these as clades (asterids
Asterids
In the APG II system for the classification of flowering plants, the name asterids refers to a clade .Most of the taxa belonging to this clade had been referred to the Asteridae in the Cronquist system and to the Sympetalae in earlier systems...
, euasterids, etc.), rather than use formal names such as subclass Asteridae.
External links
- Asteridae (Cronquist system)
- Asterids
- Phylogeny and the evolution of flower symmetry in the Asteridae
- The Phylogeny of the Asteridae sensu lato Based on Chloroplast ndhF Gene Sequences (link to abstract)
- Phylogeny of the Asteridae s. str. based on rbcL sequences, with particular reference to the Dipsacales (link to abstract)