Silversword alliance

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Dubautia linearis

Silversword alliance refers to an adaptive radiation of over 50 species in the composite or sunflower family, Asteraceae. The group is endemic to Hawaiʻi, 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. [1]

The silversword alliance is named for its most famous and visually striking members, the silverswords. There are three species of silverswords and two greenswords in the genus Argyroxiphium, confined to the islands of Maui and Hawaiʻi, and two species of Wilkesia (iliau) on Kauaʻi. The bulk of the species are placed in the genus Dubautia, which is widespread on all the main islands.

The genus Dubautia contains a wide variety of life-forms, including cushion plants, shrubs, trees, and lianas.[2]

Dubautia-silversword hybrid in Haleakalā Crater.

Similar species frequently occur in the same habitat and are often difficult to tell apart. Hybrids frequently occur between Dubautia species, and between Dubautia and Argyroxiphium. As a result, there is some disagreement over the number of species.

References[edit]

  1. ^ Carlquist, S., B. G. Baldwin, and G. D. Carr, eds. 2003. Tarweeds & Silverswords: Evolution of the Madiinae (Asteraceae). Missouri Botanical Garden Press.
  2. ^ Vickie Caraway, Gerald D. Carr and Clifford W. Morden (2001), "Assessment of hybridization and introgression in lava-colonizing Hawaiian Dubautia (Asteraceae: Madiinae) using RAPD markers", American Journal of Botany 88 (9): 1688–1694, doi:10.2307/3558414