Asterales
Encyclopedia
Asterales is an order
of dicotyledon
ous flowering plant
s that includes the composite family (Asteraceae
) and its related families.
The order is a cosmopolite
, and includes mostly herbaceous
species, although a small number of trees (such as some members of the genus Lobelia
) and shrubs are also present.
The Asterales can be characterized on the morphological and molecular level. Synapomorphies include the oligosaccharide
inulin
, a nutrient storage molecule, and unique stamen
morphology. The stamens are usually found around the style
, either aggregated densely or fused into a tube, probably an adaptation
in association with the plunger (or secondary) pollination
that is common among the families of the order.
, with about 25,000 species, and the Campanulaceae
, with about 2,000 species. The remaining families count together for less than 500 species. The two large families are cosmopolitan, with many of their species found in the northern hemisphere, and the smaller families are usually confined to Australia and the adjacent areas, or sometimes South America.
Under the Cronquist system
, Asteraceae
was the only family in the group, but newer systems (e. g. APG
II) have expanded it.
on the supercontinent Gondwana
, in the area that is now Australia and Asia. Although most extant species are herbaceous, the examination of the basal families in the order suggests that the common ancestor of the order was an arborescent plant.
Fossil evidence of the Asterales is rare and belongs to rather recent epochs, so the precise estimation of the order's age is quite difficult. An Oligocene
pollen
is known for Asteraceae and Goodeniaceae
, and seeds from Oligocene and Miocene
are known for Menyanthaceae
and Campanulaceae
respectively.
(Bremer and Gustafsson, 1997)
(Helianthus annuus), lettuce
(Lactuca sativa) and chicory
(Cichorium). Many spices and medicinal herbs are also present.
Of horticultural importance are the Asteraceae (e. g. chrysanthemum
) and Campanulaceae.
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
of dicotyledon
Dicotyledon
The dicotyledons, also known as dicots, are a group of flowering plants whose seed typically has two embryonic leaves or cotyledons. There are around 199,350 species within this group...
ous flowering plant
Flowering plant
The flowering plants , also known as Angiospermae or Magnoliophyta, are the most diverse group of land plants. Angiosperms are seed-producing plants like the gymnosperms and can be distinguished from the gymnosperms by a series of synapomorphies...
s that includes the composite 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...
) and its related families.
The order is a cosmopolite
Cosmopolitan distribution
In biogeography, a taxon is said to have a cosmopolitan distribution if its range extends across all or most of the world in appropriate habitats. For instance, the killer whale has a cosmopolitan distribution, extending over most of the world's oceans. Other examples include humans, the lichen...
, and includes mostly herbaceous
Herbaceous plant
A herbaceous plant is a plant that has leaves and stems that die down at the end of the growing season to the soil level. They have no persistent woody stem above ground...
species, although a small number of trees (such as some members of the genus Lobelia
Lobelia
Lobelia is a genus of flowering plant comprising 360–400 species, with a subcosmopolitan distribution primarily in tropical to warm temperate regions of the world, a few species extending into cooler temperate regions...
) and shrubs are also present.
The Asterales can be characterized on the morphological and molecular level. Synapomorphies include the oligosaccharide
Oligosaccharide
An oligosaccharide is a saccharide polymer containing a small number of component sugars, also known as simple sugars...
inulin
Inulin
Inulins are a group of naturally occurring polysaccharides produced by many types of plants. They belong to a class of fibers known as fructans. Inulin is used by some plants as a means of storing energy and is typically found in roots or rhizomes...
, a nutrient storage molecule, and unique stamen
Stamen
The stamen is the pollen producing reproductive organ of a flower...
morphology. The stamens are usually found around the style
Gynoecium
Gynoecium is most commonly used as a collective term for all carpels in a flower. A carpel is the ovule and seed producing reproductive organ in flowering plants. Carpels are derived from ovule-bearing leaves which evolved to form a closed structure containing the ovules...
, either aggregated densely or fused into a tube, probably an adaptation
Adaptation
An adaptation in biology is a trait with a current functional role in the life history of an organism that is maintained and evolved by means of natural selection. An adaptation refers to both the current state of being adapted and to the dynamic evolutionary process that leads to the adaptation....
in association with the plunger (or secondary) pollination
Pollination
Pollination is the process by which pollen is transferred in plants, thereby enabling fertilisation and sexual reproduction. Pollen grains transport the male gametes to where the female gamete are contained within the carpel; in gymnosperms the pollen is directly applied to the ovule itself...
that is common among the families of the order.
Families
The order Asterales includes about eleven families, the largest of which are the AsteraceaeAsteraceae
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...
, with about 25,000 species, and the Campanulaceae
Campanulaceae
The family Campanulaceae , of the order Asterales, contains about 2000 species in 70 genera of herbaceous plants, shrubs, and rarely small trees, often with milky non-toxic sap...
, with about 2,000 species. The remaining families count together for less than 500 species. The two large families are cosmopolitan, with many of their species found in the northern hemisphere, and the smaller families are usually confined to Australia and the adjacent areas, or sometimes South America.
Under 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...
, 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...
was the only family in the group, but newer systems (e. g. APG
Angiosperm Phylogeny Group
The Angiosperm Phylogeny Group, or APG, refers to an informal international group of systematic botanists who came together to try to establish a consensus on the taxonomy of flowering plants that would reflect new knowledge about plant relationships discovered through phylogenetic studies., three...
II) have expanded it.
Evolution and biogeography
The Asterales order probably originated in the CretaceousCretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
on the supercontinent Gondwana
Gondwana
In paleogeography, Gondwana , originally Gondwanaland, was the southernmost of two supercontinents that later became parts of the Pangaea supercontinent. It existed from approximately 510 to 180 million years ago . Gondwana is believed to have sutured between ca. 570 and 510 Mya,...
, in the area that is now Australia and Asia. Although most extant species are herbaceous, the examination of the basal families in the order suggests that the common ancestor of the order was an arborescent plant.
Fossil evidence of the Asterales is rare and belongs to rather recent epochs, so the precise estimation of the order's age is quite difficult. An Oligocene
Oligocene
The Oligocene is a geologic epoch of the Paleogene Period and extends from about 34 million to 23 million years before the present . As with other older geologic periods, the rock beds that define the period are well identified but the exact dates of the start and end of the period are slightly...
pollen
Pollen
Pollen is a fine to coarse powder containing the microgametophytes of seed plants, which produce the male gametes . Pollen grains have a hard coat that protects the sperm cells during the process of their movement from the stamens to the pistil of flowering plants or from the male cone to the...
is known for Asteraceae and Goodeniaceae
Goodeniaceae
Goodeniaceae are a family of flowering plants in the order Asterales. It contains about 404 species in twelve genera. The family is distributed mostly in Australia, except for the genus Scaevola, which is pantropical...
, and seeds from Oligocene and Miocene
Miocene
The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...
are known for Menyanthaceae
Menyanthaceae
Menyanthaceae are a family of aquatic and wetland plants in the order Asterales. There are approximately 60-70 species in five genera distributed worldwide. The simple or compound leaves arise alternately from a creeping rhizome. In the submersed aquatic genus Nymphoides, leaves are floating and...
and Campanulaceae
Campanulaceae
The family Campanulaceae , of the order Asterales, contains about 2000 species in 70 genera of herbaceous plants, shrubs, and rarely small trees, often with milky non-toxic sap...
respectively.
(Bremer and Gustafsson, 1997)
Economical importance
The Asteraceae include some species grown for food, including sunflowerSunflower
Sunflower is an annual plant native to the Americas. It possesses a large inflorescence . The sunflower got its name from its huge, fiery blooms, whose shape and image is often used to depict the sun. The sunflower has a rough, hairy stem, broad, coarsely toothed, rough leaves and circular heads...
(Helianthus annuus), lettuce
Lettuce
Lettuce is a temperate annual or biennial plant of the daisy family Asteraceae. It is most often grown as a leaf vegetable. It is eaten either raw, notably in salads, sandwiches, hamburgers, tacos, and many other dishes, or cooked, as in Chinese cuisine in which the stem becomes just as important...
(Lactuca sativa) and chicory
Chicory
Common chicory, Cichorium intybus, is a somewhat woody, perennial herbaceous plant usually with bright blue flowers, rarely white or pink. Various varieties are cultivated for salad leaves, chicons , or for roots , which are baked, ground, and used as a coffee substitute and additive. It is also...
(Cichorium). Many spices and medicinal herbs are also present.
Of horticultural importance are the Asteraceae (e. g. chrysanthemum
Chrysanthemum
Chrysanthemums, often called mums or chrysanths, are of the genus constituting approximately 30 species of perennial flowering plants in the family Asteraceae which is native to Asia and northeastern Europe.-Etymology:...
) and Campanulaceae.