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WonderIsland radiation fact

In Hawaii, silverswords, shrubs, cushion plants, vines and trees all descend from a single tarweed, a sticky plant of the daisy family from North America's Pacific coast, that reached the islands millions of years ago.

Silversword alliance

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The story behind the card

The ancestor belonged to the tarweeds, sticky, resinous relatives of sunflowers that grow along the Pacific coast of North America. DNA studies suggest it reached Kauaʻi about five million years ago, perhaps as a seed caught in a bird's feathers. With few competitors, its descendants spread into dry scrub, wet forest, bogs and bare lava fields, and today about 34 species in three genera make up what botanists call the silversword alliance. The best known, the silverswords themselves, form globes of silvery, sword-shaped leaves on the high volcanic slopes of Maui and Hawaiʻi Island; some species flower only once, sending up a tall stalk of flower heads before dying. Many members are now endangered, chiefly by grazing animals and invasive plants brought by people.

Türkçe oku
Hawaii'deki gümüşkılıçlar, çalılar, yastık bitkileri, sarmaşıklar ve ağaçlar, milyonlarca yıl önce adalara ulaşan tek bir atadan türedi: Kuzey Amerika'nın Pasifik kıyısından gelen, papatyagillerden yapışkan bir ot.

Ata, Kuzey Amerika'nın Pasifik kıyısında yetişen, ayçiçeğinin akrabası yapışkan ve reçineli otlardan biriydi. DNA çalışmalarına göre yaklaşık beş milyon yıl önce Kauaʻi Adası'na ulaştı; belki de bir kuşun tüylerine takılmış bir tohum olarak. Rakibi az olduğu için torunları kuru çalılıklara, yağmur ormanlarına, bataklıklara ve çıplak lav alanlarına yayıldı. Bugün botanikçilerin “gümüşkılıç grubu” dediği bu akrabalık, üç cinse ayrılan 34 kadar türden oluşur. En tanınmışları olan asıl gümüşkılıçlar, Maui ve Hawaii adalarının yüksek volkanik yamaçlarında gümüş renkli, kılıç biçimli yapraklardan küreler oluşturur. Bazı türler ömründe yalnızca bir kez çiçek açar: uzun bir çiçek sapı yükseltir, sonra ölür. Grubun pek çok üyesi bugün, insanların getirdiği otlayan hayvanlar ve istilacı bitkiler yüzünden tehlike altındadır.

Sources and further reading

Background reading: Silversword alliance
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