Argyroxiphium is a small genus of five species in the sunflower family (
AsteraceaeThe family Asteraceae or Compositae is the second largest family of flowering plants, in terms of number of species....
). Its members are known by the common name of silversword or greensword due to their long, narrow leaves and the silvery hairs on some species. It belongs to a larger radiation of over 50 species, including the physically different genera
DubautiaDubautia is a genus of flowering plant in the sunflower family, Asteraceae, that is endemic to Hawaii.It contains the following species:* Dubautia arborea - Tree Dubautia* Dubautia ciliolata* Dubautia herbstobatae* Dubautia imbricata...
and
WilkesiaWilkesia is a genus of flowering plants in the daisy family....
. This grouping is often referred to as the
silversword allianceSilversword alliance refers to an adaptive radiation of over 50 species in the composite or sunflower family, Asteraceae. The group is endemic to Hawaii, and is derived from a single immigrant to the islands....
.
These perennials are endemic to
HawaiiHawaii is the newest of the 50 U.S. states, and is the only state made up entirely of islands. It is located on an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of Australia. The state was admitted to the Union on August...
, occurring only on the islands of
MauiThe island of Maui is the second-largest of the Hawaiian Islands at 727.2 square miles and is the United States' 17th largest island. Maui is part of the state of Hawaii and is the largest of Maui County's four islands, bigger than Lānai, Kahoolawe, and Molokai...
and
HawaiiThe Island of Hawaii, also called the Big Island or Hawaii Island , is a volcanic island in the U.S. State of Hawaii in the North Pacific Ocean...
in an extremely localized distribution.
Argyroxiphium is a small genus of five species in the sunflower family (
AsteraceaeThe family Asteraceae or Compositae is the second largest family of flowering plants, in terms of number of species....
). Its members are known by the common name of silversword or greensword due to their long, narrow leaves and the silvery hairs on some species. It belongs to a larger radiation of over 50 species, including the physically different genera
DubautiaDubautia is a genus of flowering plant in the sunflower family, Asteraceae, that is endemic to Hawaii.It contains the following species:* Dubautia arborea - Tree Dubautia* Dubautia ciliolata* Dubautia herbstobatae* Dubautia imbricata...
and
WilkesiaWilkesia is a genus of flowering plants in the daisy family....
. This grouping is often referred to as the
silversword allianceSilversword alliance refers to an adaptive radiation of over 50 species in the composite or sunflower family, Asteraceae. The group is endemic to Hawaii, and is derived from a single immigrant to the islands....
.
These perennials are endemic to
HawaiiHawaii is the newest of the 50 U.S. states, and is the only state made up entirely of islands. It is located on an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of Australia. The state was admitted to the Union on August...
, occurring only on the islands of
MauiThe island of Maui is the second-largest of the Hawaiian Islands at 727.2 square miles and is the United States' 17th largest island. Maui is part of the state of Hawaii and is the largest of Maui County's four islands, bigger than Lānai, Kahoolawe, and Molokai...
and
HawaiiThe Island of Hawaii, also called the Big Island or Hawaii Island , is a volcanic island in the U.S. State of Hawaii in the North Pacific Ocean...
in an extremely localized distribution. They are primarily found above elevation in
alpine desertsThe Hawaiian tropical high shrublands are a tropical savanna ecoregion in the Hawaiian Islands. They cover an area of on the upper slopes of the volcanoes Mauna Kea, Mauna Loa, Hualālai, and Haleakalā. It includes open shrublands, grasslands, and deserts...
or bogs, indicating an adaptation to low-nutrient
soilSoil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics. It is composed of particles of broken rock that have been altered by chemical and...
s. The Kaū or Mauna Loa silversword (
A. kauense) is the most adaptable: it can be found in rocky lava flows, bogs, and open forest.
They consist of rosette-forming epigeal
shrubA shrub or bush is a horticultural rather than strictly botanical category of woody plant, distinguished from a tree by its multiple stems and lower height, usually less than 5-6 m tall. A large number of plants can be either shrubs or trees, depending on the growing conditions they experience...
s or dwarf shrubs. They may consist of a single large rosette (Mauna Kea and Haleakalā silverswords), a short-branched rosette (Mauna Loa silversword), or spreading with runners (Eke silversword, greenswords). The
flowerA flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to mediate the union of male sperm with female ovum in order to produce seeds...
heads consist of a ring of pistillate ray florets around 30 to 600 disk florets. The corolla varies in color from purplish to wine red or yellow, while the anthers are dark. A rosette will grow from 5–20 years before flowering, after which it dies. For those with a single rosette, this means the death of the plant (in contrast, those reproducing by runners rarely flower and may be very long-lived). Because they require cross pollination by insects, many plants must flower at the same time in relatively close proximity or they will fail to set seed. A significant population must exist for enough to flower each year for pollination to occur.
Despite appearances, they are very closely related to the genus
Dubautia. Although some
Dubautia are radically different from silverswords, those found in wet forest and alpine desert clearly grade into the form of silverswords. Hybrids between
Argyroxiphium sandwicense and
Dubautia menziesii are common in Haleakalā Crater. Although the two species are quite distinct, the hybrids span the entire range of variation between them.
Silverswords and greenswords are highly sensitive to disturbance. Their shallow root systems are easily crushed in the boggy soil or loose volcanic cinders they grow in. The succulent leaves are eaten by
goatThe domestic goat is a subspecies of goat domesticated from the wild goat of southwest Asia and Eastern Europe. The goat is a member of the Bovidae family and is closely related to the sheep: both are in the goat-antelope subfamily Caprinae. There are over three hundred distinct breeds of...
s in the dry summits, and pigs frequently disturb the fragile bog vegetation. All species are highly restricted in range, and even those that are protected are vulnerable to catastrophic events. 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 silverswordThe Haleakalā silversword is part of the family Asteraceae. The silversword in general is referred to as āhinahina in Hawaiian , and it has been a threatened species according to the U.S. Fish & Wildlife service since May 15, 1922...
http://www.botany.hawaii.edu/faculty/carr/avir.htm. The Mauna Kea and Mauna Loa silverswords both have small populations, but are being cultivated and outplanted in protected areas. The largest population of Mauna Loa silverswords is in Kahuku, which was recently acquired by
Hawaii Volcanoes National ParkHawaii Volcanoes National Park, established in 1916, is a United States National Park located in the U.S. State of Hawaii on the island of Hawaii. It displays the results of hundreds of thousands of years of volcanism, migration, and evolution—processes that thrust a bare land from the sea...
.
Species
- Argyroxiphium caliginis
The Eke silversword is a species of flowering plant in the Asteraceae family. It is found only in two bogs in West Maui, Hawaii. The species is threatened by damage to the bogs by rooting feral pigs, but the main population at Eke Crater is now protected by fencing -References:* Bruegmann, M.M....
C.N.Forbes-Biography:Forbes was born in Boylston, Massachusetts on 24 September 1883. When he was at the University of California he worked as a cadet for the emergency service during the 1906 San Francisco earthquake. From 1908 to 1920 he was curator of Botany at the Bernice P. Bishop Museum in Honolulu...
- Eke silversword
- Argyroxiphium grayanum - Greensword
- Argyroxiphium kauense
The Mauna Loa silversword is a species of flowering plant in the Asteraceae family. It is endemic to the eastern and southern slopes of Mauna Loa on the island of Hawaii. A. kauense occurs in a much broader range of habitats than the closely related and better-known Haleakalā silversword The...
(RockJoseph Francis Charles Rock was an Austrian-American explorer, geographer, linguist and botanist.-Life:He was born in Vienna, Austria, but moved to Honolulu, Hawaii in 1907, where he became an authority on the flora there...
& M.Neal) O.Deg. & I.Deg. - Mauna Loa or Kaū silversword
- Argyroxiphium sandwicense - silversword
- Argyroxiphium sandwicense ssp. sandwicense - Mauna Kea silversword
- Argyroxiphium sandwicense ssp. macrocephalum - Haleakalā silversword
The Haleakalā silversword is part of the family Asteraceae. The silversword in general is referred to as āhinahina in Hawaiian , and it has been a threatened species according to the U.S. Fish & Wildlife service since May 15, 1922...
- Argyroxiphium virescens
Argyroxiphium virescens was a species of flowering plant in the Asteraceae family.It was found only in the Hawaiian Islands.Its natural habitats were subtropical or tropical moist montanes and subtropical or tropical high-altitude shrubland....
- East Maui greensword (extinct)
External links