Located about 2300 miles (3680 km) from the nearest continental shore, the Hawaiian Islands are the most isolated group of islands on the planet. The plant and animal life of the Hawaiian archipelago is the result of early, very infrequent colonizations of arriving species and the slow evolution of those species—in isolation from the rest of the world's flora and fauna—over a period of at least 5 million years. As a consequence, Hawai'i is home to a large number of endemic species. The radiation of species described by Charles Darwin in the Galapagos Islands which was critical to the formulation of his theory of evolution is far exceeded in the more isolated Hawaiian Islands.
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 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".
The silversword alliance, also known as the tarweeds, refers to an adaptive radiation of around 30 species in the composite or sunflower family, Asteraceae. The group is endemic to Hawaii, and is derived from a single immigrant to the islands. For radiating from a common ancestor at an estimated 5.2±0.8 Ma, the clade is extremely diverse, composed of trees, shrubs, subshrubs, mat-plants, cushion plants, rosette plants, and lianas.
The Mauna Loa silversword, Argyroxiphium kauense, or Kaʻū silversword, is a rare species of flowering plant in the aster family. It is endemic to the eastern and southern slopes of Mauna Loa on the island of Hawaiʻi. A. kauense occurs in mountainous shrublands, bogs, and open mesic forest. The species is managed by the National Park Service and Hawaiʻi State Department of Forestry and Wildlife. It is a federally listed endangered species of the United States. There are three known populations remaining, for a total of fewer than 1000 individuals.
Dubautia herbstobatae, the Na'ena'e or Keaau Valley dubautia, is an endangered species of shrub which is endemic to Oahu, Hawaii.
Argyroxiphium grayanum, commonly known as the greensword, is a species of flowering plant in the family Asteraceae, and a member of the silversword alliance, a group of over 50 species which are diverse in morphology and habitat but are genetically closely related.
Argyroxiphium sandwicense subsp. sandwicense, the Mauna Kea silversword, is a highly endangered flowering plant endemic to the island of Hawaiʻi of Hawaii. It is the "crown jewel" of the volcanic mountain Mauna Kea, from which it derives its English name. The Hawaiian name is ʻahinahina; it applies to silverswords more broadly. The Mauna Kea silversword was once common on the volcano, and extraordinary conservation efforts are being made to preserve the species.
Cyanea kolekoleensis is a rare species of flowering plant in the bellflower family known by the common names `Oha and Kolekole cyanea. It is endemic to Kauai where it has only been seen in the Wahiawa Mountains. Like other Cyanea it is known as haha in Hawaiian.
Delissea rhytidosperma, is known by the common names Kauai delissea, Kauai leechleaf delissea, and leechleaf delissea. It is a rare species of flowering plant in the bellflower family, that is endemic to Hawaii where it is known only from the island of Kauai. It is critically endangered or extinct in the wild.
Dubautia imbricata is a rare species of flowering plant in the family Asteraceae known by the common names bog dubautia and imbricate dubautia. It is endemic to Hawaii where it is known only from the island of Kauai. There are four known occurrences. Like other Dubautia this plant is known as na`ena`e.
Dubautia kalalauensis is a rare species of flowering plant in the family Asteraceae. It is endemic to Hawaii where it is known only from the island of Kauai. There is only a single known population composed of 26 plants. It was federally listed as an endangered species of the United States in 2010. Like other Dubautia this plant is known as na`ena`e.
Dubautia kenwoodii, the Kalalau rim dubautia, is an "extremely rare" species of flowering plant in the family Asteraceae. It is endemic to Hawaii where it is known only from the island of Kauai. Only one plant has ever been seen: the type specimen. A part of this plant was collected in 1991 and the individual was described as a new species in 1998. It was federally listed as an endangered species of the United States in 2010. Like other Dubautia this plant is known as na`ena`e.
Dubautia latifolia is a rare species of flowering plant in the family Asteraceae known by the common name koholapehu. It is endemic to Hawaii where it is known only from the west side of the island of Kauai. Like other Dubautia this plant is called na`ena`e.
Dubautia plantaginea is a rare species of flowering plant in the aster family known by the common name plantainleaf dubautia. It is endemic to Hawaii where it is the only member of the silversword alliance that is found on all six of the largest islands. Two of the three subspecies are rare and endangered. Like other Dubautia this plant is called na`ena`e.
Dubautia waialealae is a rare species of flowering plant in the family Asteraceae known by the common name Wai'ale'ale dubautia. Like other Dubautia this plant is called na`ena`e.
Melicope degeneri is a rare species of flowering plant in the family Rutaceae known by the common names Kokee Stream melicope and Degener's pelea. It is endemic to Hawaii, where it is known only from the island of Kauai. It is a federally listed endangered species of the United States. Like other Hawaiian Melicope, this species is known as alani.
Myrsine linearifolia is a rare species of flowering plant in the primrose family known by the common name narrowleaf colicwood. It is endemic to Hawaii, where it is known only from the island of Kauai. There are 12 populations remaining, for a total of fewer than 200 plants. Like other Hawaiian Myrsine this plant is called kōlea. It is a federally listed threatened species of the United States.
Schiedea attenuata is a rare species of flowering plant in the family Caryophyllaceae known by the common name Kalalau schiedea. It is endemic to Hawaii, where it is known only from the Kalalau Valley on the island of Kauai. It is threatened by the degradation of its habitat. It was federally listed as an endangered species of the United States in 2010.
Dubautia syndetica, the Wahiawa dubautia, is a plant species endemic to the island of Kauai in the state of Hawaii. It is found only in the upper portions of the Wahiawa drainage basin at elevations of 680–950 m.
Argyroxiphium sandwicense subsp. macrocephalum x Dubautia menziesii, commonly known as the Dubautia-silversword, is a hybrid species of silversword plant in the family Asteraceae, and is a part of the silversword alliance. The hybrid was formed between Argyroxiphium sandwicense subsp. macrocephalum and Dubautia menziesii, which are both species of plant native to the Haleakalā Shield Volcano, Maui, primarily in the Haleakalā Crater, that grow in alpine and subalpine zones.
