Argyroxiphium grayanum
| Argyroxiphium grayanum | |
|---|---|
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| Scientific classification | |
| Kingdom: | Plantae |
| Clade: | Angiosperms |
| Clade: | Eudicots |
| Clade: | Asterids |
| Order: | Asterales |
| Family: | Asteraceae |
| Genus: | Argyroxiphium |
| Species: | A. grayanum |
| Binomial name | |
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Argyroxiphium grayanum (Hillebr.) O.Deg. |
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Argyroxiphium grayanum, commonly known as the greensword, is a species of flowering plant in the sunflower 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.
The silversword alliance provides a convincing natural case study in evolution by adaptive radiation, with the greensword representing one extreme of the genus' plasticity. Some Argyroxiphium, including the well-known Haleakala and Mauna Kea silverswords, live in harsh alpine desert-like conditions of heat, sun, wind, and aridity, and are drought-adapted plants capable of storing water as a gel in leaf structures which are normally air pockets in other plants. However, A. grayanum is a bog plant adapted to very different conditions – excessive moisture, lack of regular sunlight, and cool temperatures, and its leaves are non-succulent like those of the related genus Dubautia.
A. grayanum is a perennial plant endemic to the island of Maui in Hawaii. Its growth form is typically a low shrub up to 2 m high, erect, with an erect single-stemmed monocarpic rosette shape, though in the interior of bogs it typically grows as a dwarf shrub under 30 cm high. It has green, 5-11-nerved, narrowly elliptic-ligulate leaves which are broadest above the middle. It occurs only in and around montane cloud forest bogs at elevations ranging from about 1,200 to 2,050 m. The sites receive from about 300 to over 1,000 cm precipitation per year. It is most abundant along the upper rim of Kīpahulu Valley on East Maui and near the summit of Puʻu Kukui on West Maui. The latter region is also home to a related species, the ʻEke silversword (A. caliginis). Despite their close relationship and shared habitat, the two species differ in several ways beyond the coloring of their lance-shaped leaves, with silversword possessing a distinctive sheen.
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