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48-397: Argyrophyton Hook. Argyroxiphium is a small genus of plants in the family Asteraceae . Its members are known by the common names silversword or greensword due to their long, narrow leaves and the silvery hairs on some species. The silverswords belong to a larger radiation of over 50 species, including the physically different genera Dubautia and Wilkesia . This grouping

96-531: A clade within the Californian tarweed lineage. The relation is also physically evident—silversword capitulae and the flowers of Californian tarweeds both include sticky bracts that provide adhesion to birds for seed dispersal . It is hypothesized that an individual plant from the Californian tarweeds was spread first to Kauaʻi, then spread to the other islands and developed into the silversword alliance. Silverswords are endemic to Hawaiʻi and occur only on

144-512: A " celestial body with rays". The capitulum, which often appears to be a single flower, is often referred to as a head . In some species, the entire head is able to pivot its floral stem in the course of the day to track the sun (like a "smart" solar panel), thus maximizing the reflectivity of the entire floral unit and further attracting flying pollinators. Nearest to the flower stem lie a series of small, usually green, scale-like bracts . These are known as phyllaries ; collectively, they form

192-513: A 3+2 scheme – above the fused corolla tube, three very long fused petals form the ligule, with the other two petals being inconspicuously small. The Cichorioideae has only ray florets, with a 5+0 scheme – all five petals form the ligule. A 4+1 scheme is found in the Barnadesioideae. The tip of the ligule is often divided into teeth, each one representing a petal. Some marginal florets may have no petals at all (filiform floret). The calyx of

240-469: A different level of global extinction risk. Species that are considered to be Critically Endangered are placed within the "Threatened" category. As the IUCN Red List does not consider a species extinct until extensive targeted surveys have been conducted, species that are possibly extinct are still listed as Critically Endangered. IUCN maintains a list of "possibly extinct" and "possibly extinct in

288-418: A faster rate than that of the natural extinction rate. It has largely been credited towards human impacts on climate change and the loss of biodiversity . This is along with natural forces that may create stress on the species or cause an animal population to become extinct. Currently the biggest reason for species extinction is human interaction resulting in habitat loss. Species rely on their habitat for

336-448: A few unusual species, the "head" will consist of one single disc flower; alternatively, a few species will produce both single-flowered female heads, along with multi-flowered male heads, in their "pollination strategy". The distinguishing characteristic of Asteraceae is their inflorescence , a type of specialised, composite flower head or pseudanthium , technically called a calathium or capitulum , that may look superficially like

384-407: A method to outcompete the native organisms, eventually taking over the habitat. This can lead to either the native species' extinction or causing them to become endangered, which also eventually causes extinction. Plants and animals may also go extinct due to disease. The introduction of a disease into a new habitat can cause it to spread amongst the native species. Due to their lack of familiarity with

432-551: A ring of pistillate ray florets around 30 to 600 disk florets. The corollae vary in color from wine red to yellow or white. Because they are self-incompatible and require cross-pollination by insects , many plants must flower at the same time in relatively close proximity to set seed . A significant population must exist for enough individuals to flower simultaneously and allow pollination to occur. The single-seeded fruits are usually dispersed by wind. Despite their different appearances, silverswords are very closely related to

480-428: A scarious (dry and membranous) texture. The phyllaries can be free or fused, and arranged in one to many rows, overlapping like the tiles of a roof ( imbricate ) or not (this variation is important in identification of tribes and genera). Each floret may be subtended by a bract, called a "palea" or "receptacular bract". These bracts are often called " chaff ". The presence or absence of these bracts, their distribution on

528-480: A single floral entity is in fact a composite of much smaller flowers. The "petals" or "sunrays" in an "asteraceous" head are in fact individual strap-shaped flowers called ray flowers or ray florets , and the "sun disk" is made up of smaller, radially symmetric , individual flowers called disc flowers or disc florets . The word aster means "star" in Greek, referring to the appearance of most family members as

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576-441: A single flower. The capitulum is a contracted raceme composed of numerous individual sessile flowers , called florets , all sharing the same receptacle . A set of bracts forms an involucre surrounding the base of the capitulum. These are called "phyllaries", or "involucral bracts". They may simulate the sepals of the pseudanthium. These are mostly herbaceous but can also be brightly coloured (e.g. Helichrysum ) or have

624-420: A sort of tube around the style ( theca ). They commonly have basal and/or apical appendages. Pollen is released inside the tube and is collected around the growing style, and then, as the style elongates, is pushed out of the tube ( nüdelspritze ). The pistil consists of two connate carpels . The style has two lobes. Stigmatic tissue may be located in the interior surface or form two lateral lines. The ovary

672-591: A stem node age of 88–89 mya (Late Cretaceous, Coniacian ). Asteraceae is an economically important family, providing food staples, garden plants, and herbal medicines. Species outside of their native ranges can become weedy or invasive . Members of the Asteraceae are mostly herbaceous plants, but some shrubs, vines, and trees (such as Lachanodes arborea ) do exist. Asteraceae species are generally easy to distinguish from other plants because of their unique inflorescence and other shared characteristics, such as

720-483: Is a large family of flowering plants that consists of over 32,000 known species in over 1,900 genera within the order Asterales . The number of species in Asteraceae is rivaled only by the Orchidaceae , and which is the larger family is unclear as the quantity of extant species in each family is unknown. The Asteraceae were first described in the year 1740 and given the original name Compositae . The family

768-414: Is a two- or three-lobed, strap-shaped, individual flower, found in the head of most members of the Asteraceae. The corolla of the ray flower may have two tiny, vestigial teeth, opposite to the three-lobed strap, or tongue, indicating its evolution by fusion from an ancestral, five-part corolla. In some species, the 3:2 arrangement is reversed, with two lobes, and zero or three tiny teeth visible opposite

816-411: Is actually a composite of several much smaller flowers, known as the capitulum or head . By visually presenting as a single flower, the capitulum functions in attracting pollinators , in the same manner that other "showy" flowering plants in numerous other, older, plant families have evolved to attract pollinators. The previous name for the family, Compositae , reflects the fact that what appears to be

864-541: Is an advantage in relatively dry zones, or some combination of these and possibly other factors. Heterocarpy, or the ability to produce different fruit morphs, has evolved and is common in Asteraceae. It allows seeds to be dispersed over varying distances and each is adapted to different environments, increasing chances of survival. The original name Compositae is still valid under the International Code of Nomenclature for algae, fungi, and plants. It refers to

912-1391: Is based on Panero & Funk (2002) updated in 2014, and now also includes the monotypic Famatinanthoideae . The diamond (♦) denotes a very poorly supported node (<50% bootstrap support), the dot (•) a poorly supported node (<80%). Barnadesioideae : 9 genera, 93 species. South America , mainly the Andes . Famatinanthoideae : South America, 1 genus, 1 species Famatinanthus decussatus . Mutisioideae : 58 genera, 750 species. Absent from Europe, mostly in South America. Stifftioideae : 10 genera. South America. Wunderlichioideae : 8 genera, 24 species. Mostly in Venezuela and Guyana . Gochnatioideae : 4 or 5 genera, 90 species. Latin America and southern United States. Hecastocleidoideae : Only Hecastocleis shockleyi . Southwestern United States . Carduoideae : 83 genera, 2,500 species. Worldwide. Pertyoideae : 5 or 6 genera, 70 species. Asia. Gymnarrhenoideae : Two genera/species, Gymnarrhena micrantha ( Northern Africa , Middle East ) and Cavea tanguensis ( Eastern Himalayas ). Cichorioideae : 224 genera, 3,200 species. Worldwide. Corymbioideae : Only

960-503: Is commonly known as the aster , daisy , composite , or sunflower family . Most species of Asteraceae are herbaceous plants , and may be annual , biennial , or perennial , but there are also shrubs , vines , and trees . The family has a widespread distribution, from subpolar to tropical regions , in a wide variety of habitats. Most occur in hot desert and cold or hot semi-desert climates , and they are found on every continent but Antarctica . Their common primary characteristic

1008-533: Is compound flower heads , technically known as capitula , consisting of sometimes hundreds of tiny individual florets enclosed by a whorl of protective involucral bracts . The oldest known fossils are pollen grains from the Late Cretaceous ( Campanian to Maastrichtian ) of Antarctica, dated to c.  76–66 million years ago (mya). It is estimated that the crown group of Asteraceae evolved at least 85.9 mya (Late Cretaceous, Santonian ) with

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1056-503: Is constrained to Haleakalā on Maui while the Mauna Kea silversword ( A. sandwicense ssp. sandwicense ) is specific to Mauna Kea on Hawaiʻi. Each of the other species is found primarily at lower altitudes with much higher annual rainfall. The Mauna Loa or Kaʻū silversword ( A. kauense ) has been classified as critically endangered and the Mauna Kea and Halekalā silverswords ( A. sandwichense ) have been classified as endangered in

1104-450: Is inferior and has only one ovule , with basal placentation . In members of the Asteraceae the fruit is achene -like, and is called a cypsela (plural cypselae ). Although there are two fused carpels, there is only one locule, and only one seed per fruit is formed. It may sometimes be winged or spiny because the pappus, which is derived from calyx tissue often remains on the fruit (for example in dandelion ). In some species, however,

1152-593: Is often referred to as the silversword alliance . Botanist P. H. Raven referred to this radiation as "the best example of adaptive radiation in plants". Species in Argyroxiphium are perennial , rosette -forming shrubs . They may consist of a single large rosette or a collection of several rosettes. In all Argyroxiphium species, long, narrow leaves contain interstitial gels hypothesized to function as water storage. For some species, leaves are covered with trichomes that provide protection from frost and create

1200-524: Is the only kind of floret in the Carduoideae , while the first kind is more widespread. Ray florets are always highly zygomorphic and are characterised by the presence of a ligule , a strap-shaped structure on the edge of the corolla tube consisting of fused petals. In the Asteroideae and other minor subfamilies these are usually borne only on florets at the circumference of the capitulum and have

1248-551: The IUCN Red List . Direct damage from humans and from ungulate browsing have significantly damaged silversword populations, but dedicated management efforts have resulted in successful conservation of some species. In particular, the Haleakalā silversword population reached a low of approximately 4,000 plants in the 1920s, but rebounded to over 6,500 individuals by 1970. On the other hand, the Mauna Kea silversword population

1296-432: The involucre , which serves to protect the immature head of florets during its development. The individual florets are arranged atop a dome-like structure called the receptacle . The individual florets in a head consist, developmentally, of five fused petals (rarely four); instead of sepals , they have threadlike, hairy, or bristly structures, known collectively as a pappus , (plural pappi ). The pappus surrounds

1344-424: The "composite" nature of the capitula, which consist of a few or many individual flowers. Critically Endangered The IUCN Red List provides the public with information regarding the conservation status of animal, fungi, and plant species. It divides various species into seven different categories of conservation that are based on habitat range, population size, habitat, threats, etc. Each category represents

1392-625: The disc in irregular symmetry, or with a weakly bilaterally symmetric arrangement. A radiate head has disc flowers surrounded by ray flowers. A ligulate head has all ligulate flowers and no disc flowers. When an Asteraceae flower head has only disc flowers that are either sterile, male, or bisexual (but not female and fertile), it is a discoid head . Disciform heads possess only disc flowers in their heads, but may produce two different sex types (male or female) within their disciform head. Some other species produce two different head types: staminate (all-male), or pistillate (all-female). In

1440-613: The energy store is generally in the form of inulin rather than starch. They produce iso/ chlorogenic acid , sesquiterpene lactones , pentacyclic triterpene alcohols, various alkaloids , acetylenes (cyclic, aromatic, with vinyl end groups), tannins . They have terpenoid essential oils that never contain iridoids . Asteraceae produce secondary metabolites , such as flavonoids and terpenoids . Some of these molecules can inhibit protozoan parasites such as Plasmodium , Trypanosoma , Leishmania and parasitic intestinal worms, and thus have potential in medicine. Compositae,

1488-422: The extant genus Dasyphyllum . Barreda, et al. (2015) estimated that the crown group of Asteraceae evolved at least 85.9 mya (Late Cretaceous, Santonian ) with a stem node age of 88–89 mya (Late Cretaceous, Coniacian ). It is not known whether the precise cause of their great success was the development of the highly specialised capitulum, their ability to store energy as fructans (mainly inulin ), which

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1536-425: The florets may be absent, but when present is always modified into a pappus of two or more teeth, scales or bristles and this is often involved in the dispersion of the seeds. As with the bracts, the nature of the pappus is an important diagnostic feature. There are usually four or five stamens . The filaments are fused to the corolla, while the anthers are generally connate ( syngenesious anthers), thus forming

1584-549: The genus Corymbium , with 9 species. Cape provinces, South Africa. Asteroideae : 1,130 genera and 16,200 species. Worldwide. The family includes over 32,000 currently accepted species, in over 1,900 genera ( list ) in 13 subfamilies. The number of species in the family Asteraceae is rivaled only by Orchidaceae. Which is the larger family is unclear, because of the uncertainty about how many extant species each family includes. The four subfamilies Asteroideae , Cichorioideae , Carduoideae and Mutisioideae contain 99% of

1632-412: The genus Dubautia . Sympatric species in Argyroxiphium and Dubautia often naturally produce fertile hybrids that run the gamut of morphological characteristics from the two genera. Together, Argyroxiphium , Dubautia , and Wilkesia make up the silversword alliance. The evolutionary roots of Argyroxiphium are the tarweeds in subtribe Madiinae . DNA analysis has revealed that silverswords form

1680-401: The islands of Maui and Hawaiʻi . They grow primarily over 1,200 m (3,900 ft) above sea level in bogs , alpine shrublands , or wet shrublands . A. sandwichense is able to grow at high altitudes between 2,125 m (6,972 ft) and 3,750 m (12,300 ft) on cinder and lava with relatively little rainfall. The Haleakalā silversword ( A sandwicense ssp. macrocephalum )

1728-424: The joined anthers of the stamens . Nonetheless, determining genera and species of some groups such as Hieracium is notoriously difficult (see " damned yellow composite " for example). Members of the family Asteraceae generally produce taproots , but sometimes they possess fibrous root systems. Some species have underground stems in the form of caudices or rhizomes . These can be fleshy or woody depending on

1776-424: The leaves. Nearly all Asteraceae bear their flowers in dense flower heads called capitula . They are surrounded by involucral bracts , and when viewed from a distance, each capitulum may appear to be a single flower. Enlarged outer (peripheral) flowers in the capitulum may resemble petals, and the involucral bracts may look like a calyx. In plants of the Asteraceae, what appears to be a single "daisy"-type flower

1824-473: The original name for Asteraceae, were first described in 1740 by Dutch botanist Adriaan van Royen . Traditionally, two subfamilies were recognised: Asteroideae (or Tubuliflorae) and Cichorioideae (or Liguliflorae). The latter has been shown to be extensively paraphyletic , and has now been divided into 12 subfamilies, but the former still stands. The study of this family is known as synantherology . The phylogenetic tree of subfamilies presented below

1872-434: The ovary and can, when mature and attached to a seed, adhere to animal fur or be carried by air currents, aiding in seed dispersal . The whitish, fluffy head of a dandelion , commonly blown on by children, consists of numerous seeds resting on the receptacle, each seed attached to its pappus. The pappi provide a parachute-like structure to help the seed travel from its point of origin to a more hospitable site. A ray flower

1920-471: The pappus falls off (for example in Helianthus ). Cypsela morphology is often used to help determine plant relationships at the genus and species level. The mature seeds usually have little endosperm or none. The pollen of composites is typically echinolophate, a morphological term meaning "with elaborate systems of ridges and spines dispersed around and between the apertures." In Asteraceae,

1968-539: The plants' signature silver sheen. A silversword rosette grows for at least five years before flowering, though some species grow for up to 90 years before initiating the bolting process. For monocarpic individuals with a single rosette, this ends in the death of the plant, though some individuals are polycarpic . The flowering stalks may be up to 1.5 metres (4.9 feet) tall, and are composed of up to 600 capitulae . These flower heads range in diameter from 1 cm (0.39 in) to 6 cm (2.4 in) and consist of

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2016-440: The receptacle, and their size and shape are all important diagnostic characteristics for genera and tribes. The florets have five petals fused at the base to form a corolla tube and they may be either actinomorphic or zygomorphic . Disc florets are usually actinomorphic, with five petal lips on the rim of the corolla tube. The petal lips may be either very short, or long, in which case they form deeply lobed petals. The latter

2064-408: The resources needed for their survival. If the habitat becomes destroyed, the population will see a decline in their numbers. Activities that cause loss of habitat include pollution , urbanization , and agriculture . Another reason for plants and animals to become endangered is due to the introduction of invasive species . Invasive species invade and exploit a new habitat for its natural resources as

2112-499: The species diversity of the whole family (approximately 70%, 14%, 11% and 3% respectively). Because of the morphological complexity exhibited by this family, agreeing on generic circumscriptions has often been difficult for taxonomists . As a result, several of these genera have required multiple revisions. The oldest known fossils of members of Asteraceae are pollen grains from the Late Cretaceous of Antarctica , dated to ~76–66 mya ( Campanian to Maastrichtian ) and assigned to

2160-583: The species. The stems are herbaceous, aerial, branched, and cylindrical with glandular hairs, usually erect, but can be prostrate to ascending. The stems can contain secretory canals with resin , or latex , which is particularly common among the Cichorioideae . Leaves can be alternate , opposite , or whorled . They may be simple , but are often deeply lobed or otherwise incised, often conduplicate or revolute . The margins also can be entire or toothed . Resin or latex can also be present in

2208-446: The tongue. A ligulate flower is a five-lobed, strap-shaped, individual flower found in the heads of certain other asteraceous species. A ligule is the strap-shaped tongue of the corolla of either a ray flower or of a ligulate flower. A disk flower (or disc flower ) is a radially symmetric individual flower in the head, which is ringed by the ray flowers when both are present. In some species, ray flowers may be arranged around

2256-496: The wild" species, modelled on categories used by BirdLife International to categorize these taxa . To be defined as Critically Endangered in the Red List, a species must meet any of the following criteria (A–E) ("3G/10Y" signifies three generations or ten years—whichever is longer—over a maximum of 100 years; "MI" signifies Mature Individuals): The current extinction crisis is witnessing extinction rates that are occurring at

2304-634: Was composed of approximately 50 naturally occurring individuals and 500 outplanted individuals in 1999. The East Maui greensword ( A. virescens ) is apparently extinct , but in 1989 plants were discovered that appear to be hybrids between it and the Haleakalā silversword . The hybrid is known as the Pu'u 'Alaea greensword . now in Wilkesia Asteraceae Asteraceae ( / ˌ æ s t ə ˈ r eɪ s i . iː , - ˌ aɪ / )

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