Hawaii: The islands where evolution ran riot

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Hawaii gives a new meaning to the word “remote”. Marooned in the central Pacific, this chain of eight main islands is the only significantly-sized land for thousands of miles. If you sailed due west of Honolulu, the next thing you’d hit would be Taiwan: almost 6000 miles away.

Despite its isolation, Hawaii is anything but lonely. The archipelago boasts thousands of species of animals and plants. Most are found nowhere else on Earth, and many are startlingly different to their more familiar relatives. What was it about these islands that allowed evolution to become so creative?

The first birds to reach the islands probably arrived around 8 million years ago from east Asia.

We’ll never know exactly how these colonists made the epic journey. But once they had done so, they took to their new home like, well, like birds to empty islands.

Over the eons these founders evolved into at least 140 species of bird.

Hawaii’s equivalent of Darwin’s Galapagos finches is the Hawaiian honeycreepers, which branched into at least 56 species from just one or two. They outstrip the finches in both number and variety.

They range spectacularly in colour, from bright shades of red to muted golds and greens.

Their beaks, too, have changed shape, reflecting the different lifestyles each bird has adapted to. The beaks of the honeycreepers range from short to long; from stubby and delicate; and from straight to curved, and ingenious combinations of the two.

The insects have been even more prolific. Hawaii has more than 5000 endemic species, many of which have evolved spectacular adaptations to island life.

Although Hawaii is teeming with bird and insect life, it has very few large predators. So over millions of years, natural selection whittled away their defences.

Read more: www.bbc.com/earth/story/20150625-islands-where-evolution-ran-riot
article: Robin Wylie
photo: Katrina Brown

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