Crepis | |
---|---|
Crepis jacquinii | |
Scientific classification | |
Kingdom: | Plantae |
Clade: | Tracheophytes |
Clade: | Angiosperms |
Clade: | Eudicots |
Clade: | Asterids |
Order: | Asterales |
Family: | Asteraceae |
Subfamily: | Cichorioideae |
Tribe: | Cichorieae |
Subtribe: | Crepidinae |
Genus: | Crepis L. |
Species | |
about 200, see text |
Crepis, commonly known in some parts of the world as hawksbeard or hawk's-beard (but not to be confused with the related genus Hieracium with a similar common name), is a genus of annual and perennial flowering plants of the family Asteraceae superficially resembling the dandelion, the most conspicuous difference being that Crepis usually has branching scapes with multiple heads (though solitary heads can occur). The genus name Crepis derives from the Greek krepis, meaning "slipper" or "sandal", possibly in reference to the shape of the fruit. [1]
The genus is distributed throughout the Northern Hemisphere and Africa, [2] and several plants are known as introduced species practically worldwide. [1] The center of diversity is in the Mediterranean. [2]
Crepis species are used as food plants by the larvae of some Lepidoptera species including the broad-barred white moth. The fly Tephritis formosa is known to attack the capitula of this plant. [3]
Seeds of Crepis species are an important food source for some bird species. [4]
Crepis can reproduce sexually or asexually. Crepis is insect-pollinated, typically by bees and other generalist pollinators. [5] Species in this genus are able to produce viable seeds through hybridization. Some of these hybrids (depending on their parent species) can reproduce themselves. [6] As an aster, flowers of Crepis are closely clustered on a capitulum, which is surrounded by petal-like rays. Asexual reproduction (or autogamy) between flowers on the same capitulum has been observed in the genus. [7]
As with several other genera in Asteraceae, multiple Crepis species exhibit apomixis, a form of asexual reproduction where flowers produce clonal seeds without need of fertilization. [8] Unlike sexually-reproducing individuals, which are diploid, apomicts are typically polyploid, with three or more sets of chromosomes. [9] The mechanism of apomixis in Crepis is apospory, wherein diploid tissue arises during meiosis in the ovule. Through apospory, asexual seeds can develop spontaneously in the flowers of a non-apomictic Crepis. [10]
Crepis is part of the Cichorieae tribe in Asteraceae, and is one of several genera of that tribe that exhibits apomixis. [11] [12] [13] The largest group of asexual species is found in North America, and is referred to as the "North American Crepis agamic complex" [8] [9] The agamic complex may have first arisen in the Pliocene, between 5.3 and 2.6 million years ago. [14] At least one Eurasian Crepis species, C. tectorum, has been observed to self-fertilize. [6] Another agamic complex is thought to exist in Asia. [15] Species known to produce apomicts include C.acuminata, C.barbigera, C. intermedia, and C. occidentalis. Polyploid individuals may still be able to carry out sexual reproduction and therefore produce sexual offspring, allowing for the formation of new polyploid hybrids. [6]
Apomictic individuals can prevent reproduction in sexual individuals in multiple ways. Like other apomictic species in Cichorieae, polyploid apomicts may still produce viable pollen that can be transferred to sexual diploids through the normal process of pollination. [16] The mixed apomict-sexual parantage may produce a polyploid hybrid (as has been observed when the apomictic C. barbigera breeds with diploid species C. atribarba [17] ). Seed set in the diploid may be reduced, or the pollen may produce hybrid seeds that are unable to reproduce or survive to a normal lifespan. [18] The pollen from the apomict may also prevent germination of pollen from a diploid flower. When pollen from a polyploid individual fertilizes diploid flowers, the resultant seeds are typically polyploid, which lowers the diploid population over generations. [9]
As a result of this reproductive interference, sexual reproduction between diploid plants is reduced when apomicts enter a population. Because diploid species require pollen exchange to reproduce and apomicts can produce seeds by parthenogenesis, apomicts do not suffer any reproductive consequences in a mixed diploid-polyploid population. Meanwhile, the reproductive success of sexually-reproducing diploids falls, resulting in diploids being found more often in populations isolated from apomicts. [9]
Although apomixis has been considered a "blind alley of evolution", research into apomictic species and species complexes has cast doubt on this. Apomictic clades elsewhere in Cichorieae have demonstrated an ability to "revert" to a sexual mode of reproduction, reducing the risk of extinction through lack of introgression. [8] Speciation in Crepis has occurred through its ability to self-fertilize, hybridize, and form polyploid apomicts. [6]
Apomixis can facilitate range expansion in ways that sexual reproduction does not. Apomicts do not require input of genetic material for another individual, and can therefore produce seeds on maturity without the aid of pollinators. This allows apomictic populations to expand into new geographic areas more rapidly than sexual ones. Because apomixis in Crepis involves multiple ploidy levels, there is sufficient genetic variation for adaptation to novel ecosystems. [19] Additionally, some Crepis apomict species have the ability to hybridize with other apomicts, resulting in genetic recombination alongside parthenogenesis. [20]
In Crete, Greece the leaves of Crepis commutata which are called glykosyrida (γλυκοσυρίδα) are eaten raw, boiled, steamed or browned in salads. Another two species on the same island, Crepis vesicaria , called kokkinogoula (κοκκινογούλα), lekanida (λεκανίδα) or prikousa (πρικούσα) and a local variety called maryies (μαργιές) or pikrouses (πικρούσες) have both its leaves and tender shoots eaten boiled by the locals.[ citation needed ]
The genus Crepis is a rich source of costus lactone-type guaianolides, [21] a class of sesquiterpene lactones.
Phenolics found in Crepis include luteolin-type flavonoids and caffeoyl quinic acid derivatives such as chlorogenic acid and 3,5-dicaffeoylquinic acid. Moreover, Crepis species contain the caffeoyl tartaric acid derivatives caffeoyl tartaric acid and cichoric acid. [22]
There are about 200 species in the genus. [1] [2]
Species include:
Asexual reproduction is a type of reproduction that does not involve the fusion of gametes or change in the number of chromosomes. The offspring that arise by asexual reproduction from either unicellular or multicellular organisms inherit the full set of genes of their single parent and thus the newly created individual is genetically and physically similar to the parent or an exact clone of the parent. Asexual reproduction is the primary form of reproduction for single-celled organisms such as archaea and bacteria. Many eukaryotic organisms including plants, animals, and fungi can also reproduce asexually. In vertebrates, the most common form of asexual reproduction is parthenogenesis, which is typically used as an alternative to sexual reproduction in times when reproductive opportunities are limited. Komodo dragons and some monitor lizards can reproduce asexually.
Reproduction is the biological process by which new individual organisms – "offspring" – are produced from their "parent" or parents. There are two forms of reproduction: asexual and sexual.
Alternation of generations is the predominant type of life cycle in plants and algae. In plants both phases are multicellular: the haploid sexual phase – the gametophyte – alternates with a diploid asexual phase – the sporophyte.
In botany, apomixis is asexual development of seed or embryo without fertilization. However, other definitions include replacement of the seed by a plantlet or replacement of the flower by bulbils.
Hieracium , known by the common name hawkweed and classically as hierakion, is a genus of flowering plant in the family Asteraceae, and closely related to dandelion (Taraxacum), chicory (Cichorium), prickly lettuce (Lactuca) and sow thistle (Sonchus), which are part of the tribe Cichorieae. Hawkweeds, with their 10,000+ recorded species and subspecies, do their part to make Asteraceae the second largest family of flowering plants. Some botanists group all these species or subspecies into approximately 800 accepted species, while others prefer to accept several thousand species. Since most hawkweeds reproduce exclusively asexually by means of seeds that are genetically identical to their mother plant, clones or populations that consist of genetically identical plants are formed and some botanists prefer to accept these clones as good species whereas others try to group them into a few hundred more broadly defined species. What is here treated as the single genus Hieracium is now treated by most European experts as two different genera, Hieracium and Pilosella, with species such as Hieracium pilosella, Hieracium floribundum and Hieracium aurantiacum referred to the latter genus. Many members of the genus Pilosella reproduce both by stolons and by seeds, whereas true Hieracium species reproduce only by seeds. In Pilosella, many individual plants are capable of forming both normal sexual and asexual (apomictic) seeds, whereas individual plants of Hieracium only produce one kind of seeds. Another difference is that all species of Pilosella have leaves with smooth (entire) margins whereas most species of Hieracium have distinctly dentate to deeply cut or divided leaves.
A dry roadside dotted with small, ¾ inch red orange flowers, interspersed with very similar yellow ones, and often the white of daisies, is a good sign that you are in Hawkweed country.
Plant reproductive morphology is the study of the physical form and structure of those parts of plants directly or indirectly concerned with sexual reproduction.
Double fertilization or double fertilisation is a complex fertilization mechanism of angiosperms. This process involves the fusion of a female gametophyte or megagametophyte, also called the embryonic sac, with two male gametes (sperm). It begins when a pollen grain adheres to the stigmatic surface of the carpel, the female reproductive structure of angiosperm flowers. The pollen grain begins to germinate, forming a pollen tube that penetrates and extends down through the style toward the ovary as it follows chemical signals released by the egg. The tip of the pollen tube then enters the ovary by penetrating through the micropyle opening in the ovule, and releases two sperm into the embryonic sac (megagametophyte).
A polyploid complex, also called a diploid-polyploid complex, is a group of interrelated and interbreeding species that also have differing levels of ploidy that can allow interbreeding.
Plant reproduction is the production of new offspring in plants, which can be accomplished by sexual or asexual reproduction. Sexual reproduction produces offspring by the fusion of gametes, resulting in offspring genetically different from either parent. Asexual reproduction produces new individuals without the fusion of gametes, resulting in clonal plants that are genetically identical to the parent plant and each other, unless mutations occur.
Nucellar embryony is a form of seed reproduction that occurs in certain plant species, including many citrus varieties. Nucellar embryony is a type of apomixis, where eventually nucellar embryos from the nucellus tissue of the ovule are formed, independent of meiosis and sexual reproduction. During the development of seeds in plants that possess this genetic trait, the nucellus tissue which surrounds the megagametophyte can produce nucellar cells, also termed initial cells. These additional embryos (polyembryony) are genetically identical to the parent plant, rendering them as clones. By contrast, zygotic seedlings are sexually produced and inherit genetic material from both parents. Most angiosperms reproduce sexually through double fertilization. Different from nucellar embryony, double fertilization occurs via the syngamy of sperm and egg cells, producing a triploid endosperm and a diploid zygotic embryo. In nucellar embryony, embryos are formed asexually from the nucellus tissue. Zygotic and nucellar embryos can occur in the same seed (monoembryony), and a zygotic embryo can divide to produce multiple embryos. The nucellar embryonic initial cells form, divide, and expand. Once the zygotic embryo becomes dominant, the initial cells stop dividing and expanding. Following this stage, the zygotic embryo continues to develop and the initial cells continue to develop as well, forming nucellar embryos. The nucellar embryos generally end up outcompeting the zygotic embryo, rending the zygotic embryo dormant. The polyembryonic seed is then formed by the many adventitious embryos within the ovule. The nucellar embryos produced via apomixis inherit its mother's genetics, making them desirable for citrus propagation, research, and breeding.
Taraxacum officinale, the dandelion or commondandelion, is a herbaceous perennial flowering plant in the daisy family Asteraceae. The common dandelion is well known for its yellow flower heads that turn into round balls of many silver-tufted fruits that disperse in the wind. These balls are called "clocks" in both British and American English. The name "blowball" is also used.
Crepis monticola is a North American species of flowering plant in the family Asteraceae known by the common name mountain hawksbeard.
The Cichorieae are a tribe in the plant family Asteraceae that includes 93 genera, more than 1,600 sexually reproductive species and more than 7,000 apomictic species. They are found primarily in temperate regions of the Eastern Hemisphere. Cichorieae all have milky latex and flowerheads that only contain one type of floret. The genera Gundelia and Warionia only have disk florets, while all other genera only have ligulate florets. The genera that contain most species are Taraxacum with about 1,600 apomictic species, Hieracium with about 770 sexually reproducing and 5,200 apomictic species, and Pilosella with 110 sexually reproducing and 700 apomictic species. Well-known members include lettuce, chicory, dandelion, and salsify.
Taraxacum is a large genus of flowering plants in the family Asteraceae, which consists of species commonly known as dandelions. The scientific and hobby study of the genus is known as taraxacology. The genus is native to Eurasia but the two most commonplace species worldwide, T. officinale and T. erythrospermum, were introduced from Europe into North America, where they are an invasive species. Dandelions thrive in temperate regions and can be found in yards, gardens, sides of roads, among crops, and in many other habitats. Both species are edible in their entirety and have a long history of consumption. The common name dandelion is also given to specific members of the genus.
Antennaria rosea is a North American species of flowering plant in the family Asteraceae known by the common name rosy pussytoes. Other common names include cat's foot and mountain everlasting. The second part of its scientific name, rosea, is Latin for pink.
Crepis paludosa, the marsh hawk's-beard, is a European species of flowering plant in the tribe Cichorieae of the family Asteraceae. It is widespread across much of Europe with isolated populations in Iceland, the Ural Mountains, and the Caucasus.
Pseudogamy refers to aspects of reproduction. It has different meanings in zoology and in botany.
Crepis tectorum, commonly referred to as the narrowleaf hawksbeard or narrow-leaved hawk's-beard, is an annual or winter annual plant between 30 and 100 centimetres in height. Originating in Siberia before being introduced to Canada in 1890, the narrowleaf hawksbeard's is an invasive species. Maintaining one branched, hairless and leafy stem during maturity, the narrowleaf hawksbeard has yellow leaves which are arranged in an alternate manner and less than 0.5 inches (13 mm) wide.
A compilospecies is a genetically aggressive species which acquires the heredities of a closely related sympatric species by means of hybridisation and comprehensive introgression. The target species may be incorporated to the point of despeciation, rendering it extinct. This type of genetic aggression is associated with species in newly disturbed habitats, weed species and domestication. They can be diploid or polyploid, as well as sexual or primarily asexual. The term compilospecies derives from the Latin word compilo, which means to seize, to collect, to rob or to plunder. A proposed explanation for the existence of such a species with weak reproductive barriers and frequent introgression is that it allows for genetic variation. An increase in the gene pool through viable hybrids can facilitate new phenotypes and the colonisation of novel habitats. The concept of compilospecies is not frequent in scientific literature and may not be fully regarded by the biological community as a true evolutionary concept, especially due to low supporting evidence.
Crepis vesicaria is a European species of flowering plant in the family Asteraceae with the common name beaked hawk's-beard. It is native to the Western and Southern Europe from Ireland and Portugal east as far as Germany, Austria, and Greece. It became naturalized in scattered locations in North America.
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