Asclepias

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Asclepias
Danaus plexippus on Asclepias incarnata 4999.jpg
Asclepias incarnata (swamp milkweed) flowers and a monarch butterfly
Scientific classification OOjs UI icon edit-ltr.svg
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Asterids
Order: Gentianales
Family: Apocynaceae
Subfamily: Asclepiadoideae
Tribe: Asclepiadeae
Subtribe: Asclepiadinae
Genus: Asclepias
L. [1]
Type species
Asclepias syriaca
L.
Species [2]

See List of Asclepias species

Synonyms [3]
List
  • Acerates Elliott
  • AcerotisRaf.
  • AceratesStopp
  • Anantherix Nutt.
  • AnthanotisRaf.
  • Asclepiodella Small
  • Asclepiodora A.Gray
  • BiventrariaSmall
  • CrassaRuppius
  • DassoviaNeck.
  • OdontostelmaRendle
  • OligoronRaf.
  • OnistisRaf.
  • OtanemaRaf.
  • OtariaKunth
  • Oxypteryx Greene
  • PodostemmaGreene
  • PodostigmaElliott
  • PolyotusNutt.
  • SchizonotusA.Gray
  • SolanoaGreene
  • SolanoanaKuntze
  • StylandraNutt.
  • Trachycalymma(K.Schum.) Bullock

Asclepias is a genus of herbaceous, perennial, flowering plants known as milkweeds, named for their latex, a milky substance containing cardiac glycosides termed cardenolides, exuded where cells are damaged. [4] [5] [6] Most species are toxic to humans and many other species, primarily due to the presence of cardenolides. However, as with many such plants, some species feed upon milkweed leaves or the nectar from their flowers. A noteworthy feeder on milkweeds is the monarch butterfly, which uses and requires certain milkweeds as host plants for their larvae.

Contents

The Asclepias genus contains over 200 species distributed broadly across Africa, North America, and South America. [7] It previously belonged to the family Asclepiadaceae, which is now classified as the subfamily Asclepiadoideae of the dogbane family, Apocynaceae.

The genus was formally described by Carl Linnaeus in 1753, [8] who named it after Asclepius, the Greek god of healing. [9]

Flowers

A monarch butterfly on swamp milkweed Monarch Butterfly Danaus plexippus Milkweed.jpg
A monarch butterfly on swamp milkweed
Asclepias syriaca seed pods, upper image from August and lower from December Asclepias syriaca seed pod.jpg
Asclepias syriaca seed pods, upper image from August and lower from December
Milkweed sprout, a few days after sowing Milkweed sprout.jpg
Milkweed sprout, a few days after sowing
Chemical structure of oleandrin, one of the cardiac glycosides Oleandrin-skeletal.svg
Chemical structure of oleandrin, one of the cardiac glycosides

Members of the genus produce some of the most complex flowers in the plant kingdom, comparable to orchids in complexity. Five petals reflex backwards revealing a gynostegium surrounded by a five-membrane corona. The corona is composed of a five-paired hood-and-horn structure with the hood acting as a sheath for the inner horn. Glands holding pollinia are found between the hoods. The size, shape and color of the horns and hoods are often important identifying characteristics for species in the genus Asclepias. [10]

Pollination in this genus is accomplished in an unusual manner. Pollen is grouped into complex structures called pollinia (or "pollen sacs"), rather than being individual grains or tetrads, as is typical for most plants. The feet or mouthparts of flower-visiting insects, such as bees, wasps, and butterflies, slip into one of the five slits in each flower formed by adjacent anthers. The bases of the pollinia then mechanically attach to the insect, so that a pair of pollen sacs can be pulled free when the pollinator flies off, assuming the insect is large enough to produce the necessary pulling force (if not, the insect may become trapped and die). [11] Pollination is effected by the reverse procedure, in which one of the pollinia becomes trapped within the anther slit. Large-bodied hymenopterans (bees, wasps) are the most common and best pollinators, accounting for over 50% of all Asclepias pollination, [12] whereas monarch butterflies are poor pollinators of milkweed. [5]

Male Pepsis grossa, a typical milkweed-pollinating wasp Pepsis sp 02.jpg
Male Pepsis grossa , a typical milkweed-pollinating wasp
Honeybee on antelope horn (Asclepias asperula) showing pollinia attached to legs Bee on Antelope Horn-April 2015.JPG
Honeybee on antelope horn ( Asclepias asperula ) showing pollinia attached to legs
milkweed seeds dispersed by the wind.

Asclepias species produce their seeds in pods termed follicles. The seeds, which are arranged in overlapping rows, bear a cluster of white, silky, filament-like hairs known as the coma [13] (often referred to by other names such as pappus, "floss", "plume", or "silk"). The follicles ripen and split open, and the seeds, each carried by its coma, are blown by the wind. Some, but not all, milkweeds also reproduce by clonal (or vegetative) reproduction.

Selected species

ImageScientific nameCommon nameDistribution
Asclepias-albicans.jpg Asclepias albicans Whitestem milkweedNative to the Mojave and Sonoran deserts
Asclepias amplexicaulis Arkansas.jpg Asclepias amplexicaulis Blunt-leaved milkweedNative to central and eastern United States
Asclepias asperula - Antelope Horns.jpg Asclepias asperula Antelope horns Native to American southwest and northern Mexico
Asclepias sp. flowers (Marshal Hedin).jpg Asclepias californica California milkweedNative to central and southern California
Asclepias cordifolia.JPG Asclepias cordifolia Heart-leaf milkweed Native to the Sierra Nevada and Cascade Range up to 2,000 m (6,600 ft).
Asclepiascryptoceras.jpg Asclepias cryptoceras Pallid milkweedNative to the western United States.
Asclepias curassavica (Mexican Butterfly Weed) W IMG 1570.jpg Asclepias curassavica Scarlet milkweed, tropical milkweed, bloodflower, bastard ipecacuanhaNative to the American tropics, introduced to other continents
Asclepias curtissii (Curtiss milkweed ) (5771618293).jpg Asclepias curtissii Curtiss's milkweedEndemic to sandy areas of Florida
Asclepiaseriocarpa.jpg Asclepias eriocarpa Woollypod milkweedNative to California, Baja California, and Nevada
Asclepias erosa 5.jpg Asclepias erosa Desert milkweedNative to California, Arizona, and Baja California
Asclepias exaltata (2985661678).jpg Asclepias exaltata Poke milkweedNative to eastern North America
Asclepias fascicularis.jpg Asclepias fascicularis Narrow-leaf milkweedNative to Western United States
Asclepias hirtella arkansas.jpg Asclepias hirtella Tall green milkweed
Asclepias humistrata.jpg Asclepias humistrata Sandhill milkweedNative to southeastern United States
Swamp Milkweed Asclepias incarnata Flowers Closeup 2800px.jpg Asclepias incarnata Swamp milkweedNative to wetlands of North America
Asclepias lanceolata plant.jpg Asclepias lanceolata Lanceolate milkweed (Cedar Hill milkweed)Native to coastal plain of eastern United States from Texas to New Jersey
Asclepias linaria.jpg Asclepias linaria Pine needle milkweedNative to Mojave and Sonoran deserts
Asclepiasmeadii.jpg Asclepias meadii Mead's milkweedNative to midwestern United States
Asclepias nyctaginifolia.jpg Asclepias nyctaginifolia Mojave milkweednative to the American southwest
Purple Milkweed Asclepias purpurascens Head.jpg Asclepias purpurascens Purple milkweedNative to eastern, southern, and midwestern United States
Closeup of Asclepias prostrata in flower.jpg Asclepias prostrata Prostrate milkweedNative to Texas and northern Mexico
Asclepias quadrifolia.jpg Asclepias quadrifolia Four-leaved milkweedNative to eastern United States and Canada
BB-3386 Asclepias rubra.png Asclepias rubra Red milkweed
Asclepias solanoana.jpeg Asclepias solanoana Serpentine milkweedNative to northern California
R27182818 milkweed img 0312.jpg Asclepias speciosa Showy milkweedNative to western United States and Canada
Asclepias subulata flowers 2.jpg Asclepias subulata Rush milkweedNative to southwestern North America
Asclepias subverticillata.jpg Asclepias subverticillata Horsetail milkweed [14]
Asclepias sullivantii.jpg Asclepias sullivantii Sullivant's milkweed
Common milkweed-tracy.jpg Asclepias syriaca Common milkweed
Asclepias texana.jpg Asclepias texana Texas milkweed
Butterfly Weed Asclepias tuberosa Umbel.jpg Asclepias tuberosa Butterfly weed, pleurisy root
Asclepias uncialis lg.jpg Asclepias uncialis Wheel milkweed
Asclepias variegata 2.jpg Asclepias variegata White milkweed
Asclepias verticillata Arkansas.jpg Asclepias verticillata Whorled milkweed
Asclepias viridiflora Arkansas.jpg Asclepias viridiflora Green milkweed
Asclepias viridis Arkansas.jpg Asclepias viridis Green antelopehorn, spider milkweed
Asclepias welshii 1.jpg Asclepias welshii Welsh's milkweed

There are also 12 species of Asclepias in South America, among them: A. barjoniifolia , A. boliviensis , A. curassavica , A. mellodora , A. candida , A. flava , and A. pilgeriana .

Ecology

Milkweeds are an important nectar source for native bees, wasps, and other nectar-seeking insects, though non-native honey bees commonly get trapped in the stigmatic slits and die. [11] [15] Milkweeds are also the larval food source for monarch butterflies and their relatives, as well as a variety of other herbivorous insects (including numerous beetles, moths, and true bugs) specialized to feed on the plants despite their chemical defenses. [5]

Milkweeds use three primary defenses to limit damage caused by caterpillars: hairs on the leaves (trichomes), cardenolide toxins, and latex fluids. [16] Data from a DNA study indicate that, generally, more recently evolved milkweed species ("derived" in botany parlance) use these preventive strategies less but grow faster than older species, potentially regrowing faster than caterpillars can consume them. [17] [18] [19]

Research indicates that the very high cardenolide content of Asclepias linaria reduces the impact of the Ophryocystis elektroscirrha (OE) parasite on the monarch butterfly, Danaus plexippus . The OE parasite causes holes to form in the wings of fully developed monarch butterflies. This causes weakened endurance and an inability to migrate. The parasite only infects monarchs when they are larvae and caterpillars, but the detriment is when they are in their butterfly form. [20] By contrast, some species of Asclepias are extremely poor sources of cardenolides, such as Asclepias fascicularis , Asclepias tuberosa , and Asclepias angustifolia.[ citation needed ]

Monarch butterfly conservation and milkweeds

The leaves of Asclepias species are a food source for monarch butterfly larvae and some other milkweed butterflies. [5] These plants are often used in butterfly gardening and monarch waystations in an effort to help increase the dwindling monarch population. [21]

However, some milkweed species are not suitable for butterfly gardens and monarch waystations. For example, A. curassavica , or tropical milkweed, is often planted as an ornamental in butterfly gardens outside of its native range of Mexico and Central America. Year-round plantings of this species in the United States are controversial and criticised, as they may lead to new overwintering sites along the U.S. Gulf Coast and the consequent year-round breeding of monarchs. [22] This is thought to adversely affect migration patterns, and to cause a dramatic build-up of the dangerous parasite, Ophryocystis elektroscirrha . [23] New research also has shown that monarch larvae reared on tropical milkweed show reduced migratory development (reproductive diapause), and when migratory adults are exposed to tropical milkweed, it stimulates reproductive tissue growth. [24]

Because of this, it is most often suggested to grow milkweeds that are native to the geographical area they are planted in to prevent negative impacts on monarch butterflies. [25] [26]

Monarch caterpillars do not favor butterfly weed ( A. tuberosa ), perhaps because the leaves of that milkweed species contain very little cardenolide. [27] Some other milkweeds may have similar characteristics.

Uses

Milkweeds are not grown commercially in large scale, but the plants have had many uses throughout human history. [5] Milkweeds have a long history of medicinal, every day, and military use. The Omaha people from Nebraska, the Menomin from Wisconsin and upper Michigan, the Dakota from Minnesota, and the Ponca people from Nebraska, traditionally used common milkweed ( A. syriaca ) for medicinal purposes.[ citation needed ] The bast fibers of some species can be used for rope. The Miwok people of northern California used heart-leaf milkweed ( A. cordifolia ) for its stems, which they dried and used for cords, strings and ropes. [28]

The fine, silky fluff attached to milkweed seeds, which allows them to be distributed long distances on the wind, is known as floss. Milkweed floss is incredibly difficult to spin due to how short and smooth the filaments are, but blending it with as little as 25% wool or other fiber can produce workable yarn. [29]

A study of the insulative properties of various materials found that milkweed floss was outperformed by other materials in terms of insulation, loft, and lumpiness, but it scored well when mixed with down feathers. [30] The milkweed filaments from the coma (the "floss") are hollow and coated with wax, and have good insulation qualities. During World War II, more than 5,000 t (5,500 short tons) of milkweed floss was collected in the US as a substitute for kapok in life jackets. [31] [32] Milkweed is grown commercially as a hypoallergenic filling for pillows [33] and as insulation for winter coats. [34] Using milkweed floss for these purposes could provide a plant-based alternative to down and promote the growth of milkweed in areas where it has declined, though there is some concern that the environmental impacts could be negative if monoculture is used. [35] Asclepias is also known as "Silk of America" [36] which is a strand of common milkweed (A. syriaca) gathered mainly in the valley of the Saint Lawrence River in Canada. Milkweed floss can be used in thermal insulation and acoustic insulation. The floss is also highly buoyant and water-repellent, but absorbs oil readily. [37] Due to its oil-absorbing properties, it can be used for oil spill cleanup. [38] [39] [40]

Seeds of Asclepias syriaca (Common Milkweed) Milkweed-in-seed2.jpg
Seeds of Asclepias syriaca (Common Milkweed)

Milkweed latex contains about two percent latex, and during World War II both Nazi Germany and the US attempted to use it as a source of natural rubber, although no record of large-scale success has been found. [41]

Many milkweed species also contain cardiac glycoside poisons that inhibit animal cells from maintaining a proper K+, Ca2+ concentration gradient. [6] As a result, many peoples of South America and Africa used arrows poisoned with these glycosides to fight and hunt more effectively. Some milkweeds are toxic enough to cause death when animals consume large quantities of the plant. Some milkweeds also cause mild dermatitis in some who come in contact with them. Nonetheless, some species can be made edible if properly processed. [5]

Related Research Articles

<i>Erysimum</i> Genus of flowering plants

Erysimum, or wallflower, is a genus of flowering plants in the cabbage family, Brassicaceae. It includes more than 150 species, both popular garden plants and many wild forms. Erysimum is characterised by star-shaped and/or two-sided) trichomes growing from the stem, with yellow, red, pink or orange flowers and multiseeded seed pods.

<i>Asclepias tuberosa</i> Species of flowering plant

Asclepias tuberosa, commonly known as butterfly weed, is a species of milkweed native to eastern and southwestern North America. It is commonly known as butterfly weed because of the butterflies that are attracted to the plant by its color and its copious production of nectar.

<span class="mw-page-title-main">Monarch butterfly</span> Milkweed butterfly in the family Nymphalidae

The monarch butterfly or simply monarch is a milkweed butterfly in the family Nymphalidae. Other common names, depending on region, include milkweed, common tiger, wanderer, and black-veined brown. It is among the most familiar of North American butterflies and an iconic pollinator, although it is not an especially effective pollinator of milkweeds. Its wings feature an easily recognizable black, orange, and white pattern, with a wingspan of 8.9–10.2 cm (3.5–4.0 in). A Müllerian mimic, the viceroy butterfly, is similar in color and pattern, but is markedly smaller and has an extra black stripe across each hindwing.

<i>Asclepias syriaca</i> Species of flowering plant

Asclepias syriaca, commonly called common milkweed, butterfly flower, silkweed, silky swallow-wort, and Virginia silkweed, is a species of flowering plant. It is native to southern Canada and much of the United States east of the Rocky Mountains, excluding the drier parts of the prairies. It is in the genus Asclepias, the milkweeds. It grows in sandy soils as well as other kinds of soils in sunny areas.

<i>Asclepias incarnata</i> Species of flowering plant

Asclepias incarnata, the swamp milkweed, rose milkweed, rose milkflower, swamp silkweed, or white Indian hemp, is a herbaceous perennial plant species native to North America. It grows in damp through wet soils and also is cultivated as a garden plant for its flowers, which attract butterflies and other pollinators with nectar. Like most other milkweeds, it has latex containing toxic chemicals, a characteristic that repels insects and other herbivorous animals.

<span class="mw-page-title-main">Queen (butterfly)</span> Species of butterfly

The queen butterfly is a North and South American butterfly in the family Nymphalidae with a wingspan of 80–85 mm. It is orange or brown with black wing borders and small white forewing spots on its dorsal wing surface, and reddish ventral wing surface fairly similar to the dorsal surface. The ventral hindwings have black veins and small white spots in a black border. The male has a black androconial scent patch on its dorsal hindwings. It can be found in meadows, fields, marshes, deserts, and at the edges of forests.

<span class="mw-page-title-main">Butterfly gardening</span> Gardening to benefit butterflies

Butterfly gardening is a way to create, improve, and maintain habitat for lepidopterans including butterflies, skippers, and moths. Butterflies have four distinct life stages—egg, larva, chrysalis, and adult. In order to support and sustain butterfly populations, an ideal butterfly garden contains habitat for each life stage.

<i>Asclepias asperula</i> Species of flowering plant

Asclepias asperula, commonly called antelope horns milkweed or spider milkweed, is a species of milkweed native to the Southwestern United States and northern Mexico.

<i>Tetraopes tetrophthalmus</i> Species of beetle

Tetraopes tetrophthalmus, the red milkweed beetle, is a beetle in the family Cerambycidae.

<i>Asclepias curassavica</i> Species of flowering plant

Asclepias curassavica, commonly known as tropical milkweed, is a flowering plant species of the milkweed genus, Asclepias. It is native to the American tropics and has a pantropical distribution as an introduced species. Other common names include bloodflower or blood flower, cotton bush, hierba de la cucaracha, Mexican butterfly weed, redhead, scarlet milkweed, and wild ipecacuanha.

<i>Asclepias purpurascens</i> Species of flowering plant

Asclepias purpurascens, the purple milkweed, is a herbaceous plant species. It is in the genus Asclepias, making it a type of milkweed. It is native to the Eastern, Southern and Midwestern United States similar to the range of the common milkweed. The plant gets its name from the flowers that first develop a pink color but then turn darker purple as they mature. Unlike common milkweed, purple milkweed prefers some shade and is considered a plant of partial shade. It is also considered an indicator of oak savanna, especially in Wisconsin. The species rarely produces seed pods which are smooth, instead of the rough warty ones produced by common milkweed.

<span class="mw-page-title-main">Cardenolide</span> Chemical compound

A cardenolide is a type of steroid. Many plants contain derivatives, collectively known as cardenolides, including many in the form of cardenolide glycosides (cardenolides that contain structural groups derived from sugars). Cardenolide glycosides are often toxic; specifically, they are heart-arresting. Cardenolides are toxic to animals through inhibition of the enzyme Na+/K+-ATPase, which is responsible for maintaining the sodium and potassium ion gradients across the cell membranes.

<i>Asclepias verticillata</i> Species of flowering plant

Asclepias verticillata, the whorled milkweed, eastern whorled milkweed, or horsetail milkweed, is a species of milkweed native to most of eastern North America and parts of western Canada and the United States.

<i>Calotropis gigantea</i> Species of plant

Calotropis gigantea, the crown flower, is a species of Calotropis native to Cambodia, Vietnam, Bangladesh, Indonesia, Malaysia, Thailand, Sri Lanka, India, China, Pakistan, and Nepal.

<i>Erysimum cheiranthoides</i> Species of flowering plant

Erysimum cheiranthoides, the treacle-mustard,wormseed wallflower, or wormseed mustard is a species of Erysimum native to most of central and northern Europe and northern and central Asia. Like other Erysimum species, E. cheiranthoides accumulates two major classes of defensive chemicals: glucosinolates and cardiac glycosides.

<i>Asclepias meadii</i> Species of flowering plant

Asclepias meadii is a rare species of milkweed known by the common name Mead's milkweed. It is native to the American Midwest, where it was probably once quite widespread in the tallgrass prairie. Today much of the Midwest has been fragmented and claimed for agriculture, and the remaining prairie habitat is degraded.

<i>Asclepias lanceolata</i> Species of plant

Asclepias lanceolata, the fewflower milkweed, is a species of milkweed that is native to the coastal plain of the United States from New Jersey to Florida and Southeast Texas. A. lanceolata is an upright, perennial plant that can grow between 3 and 5 feet tall, with red-orange flowers blooming in the summer months. It can also be referred to as Cedar Hill milkweed, as it was first described by Dr. Eli Ives in the neighborhood of Cedar Hill in New Haven, Connecticut.

<i>Asclepias sullivantii</i> Species of plant

Asclepias sullivantii is a species of flowering plant in the milkweed genus, Asclepias. Common names include prairie milkweed, Sullivant's milkweed, and smooth milkweed. It is native to North America, where it occurs in the central United States and Ontario in Canada.

<i>Asclepias curtissii</i> Species of plant

Asclepias curtissii, or Curtiss's milkweed, is a rare species of flowering milkweed that is endemic to Florida's sandy areas. Curtiss's milkweed belongs to the subfamily Asclepiadoideae and the genus Asclepias. This dicotyledonous, perennial plant was placed on the endangered species list by the state of Florida to protect this rare milkweed. Although Curtiss milkweed is found all over Florida, the populations are very isolated and concentrated.

<span class="mw-page-title-main">Calotropin</span> Chemical compound

Calotropin is a toxic cardenolide found in plants in the family Asclepiadoideae. In extreme cases, calotropin poisoning can cause respiratory and cardiac failure. Accidental poisoning is common in livestock who have ingested milkweed. Calotropin is commonly stored as a defense mechanism by insects that eat milkweeds as their main food source.

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