Flightless insects evolve on windy islands, just as Charles Darwin claimed — although for reasons that are slightly different to those proposed by the naturalist.
Darwin argued some 160 years ago that natural selection favours flightless bugs on windy islands, as they are less likely to end up being blown out to sea.
However, his ideas at the time were dismissed by his scientific rivals.
Researchers from Australia have now found, based on their study of insects on some of the world’s windiest islands, that Darwin was indeed on to something.
However, the advantage to flightless insects comes not from avoiding a watery death, but from being able to focus more of their energy on reproduction.
Flightless insects evolved to avoid being blown away to sea, a study has concluded, validating a 160-year-old theory first propounded by Charles Darwin. Pictured, a flightless moth — with visibly reduced wings — from Marion Island in the Southern Ocean
In her study, biologist Rachel Leihy and Steven Chown of Australia’s Monash University analysed data on insects battered by the so-called ‘roaring forties’ and ‘furious fifties’.
These are powerful winds which tear across the ocean and islands between Antarctica and Australia at latitudes between 40–50°.
On these islands, many flies and moths have wings that are diminished or absent — and crawl around rather than flying.
Because windy conditions make insect flight more energy intensive, the bugs stop bothering with flight, the team concluded.
Eventually, these insects stop producing wings and wing muscles altogether, allowing them to redirect their precious resources to mating instead.
‘Of course, Charles Darwin knew about this wing loss habit of island insects. He and the famous botanist Joseph Hooker had a substantial argument about why this happens,’ explained Ms Leihy.
‘Darwin’s position was deceptively simple. If you fly, you get blown out to sea.’
‘Those left on land to produce the next generation are those most reluctant to fly, and eventually evolution does the rest. Voilà.’
The naturalist Charles Darwin, pictured — father of the theory of evolution — argued that natural selection favours flightless insects on windy islands, as they are more likely to survive
‘If Darwin really got it wrong, then wind would not in any way explain why so many insects have lost their ability to fly on these islands,’ Ms Leihy continued.
‘It’s remarkable that — after 160 years — Darwin’s ideas continue to bring insight to ecology,’ she concluded.
The full findings of the study were published in the journal Proceedings of the Royal Society B.
CHARLES DARWIN: THE BRITISH NATURALIST WHO INTRODUCED THE IDEA OF NATURAL SELECTION
Charles Darwin (1809-1882)
Charles Robert Darwin was born in Shrewsbury, Shropshire, the fifth of six children of wealthy and well-connected parents.
One of his grandfathers was Erasmus Darwin, a doctor whose book ‘Zoonomia’ had set out a radical and highly controversial idea, that one species could ‘transmute’ into another. Transmutation is what evolution was then known as.
In 1825, Charles Darwin studied at Edinburgh University, one of the best places in Britain to study science.
It attracted free thinkers with radical opinions including, among other things, theories of transmutation.
Darwin trained to be a clergyman in Cambridge in 1827 after abandoning his plans to become a doctor, but continued his passion for biology.
In 1831, Charles’ tutor recommended he go on a voyage around the world on HMS Beagle.
Over the next five years Darwin travelled five continents collecting samples and specimens while investigating the local geology.
With long periods of nothing to do but reflect and read, he studied Charles Lyell’s Principles of Geology, which had a profound impact.
The trip also began a life of illness after he suffered terrible sea sickness.
In 1835, HMS Beagle made a five-week stop at the Galapágos Islands, 600 miles off the coast of Ecuador.
There, he studied finches, tortoises and mockingbirds although not in enough detail to come to any great conclusions.
But he was beginning to accumulate observations which were fast building up.
On returning home in 1838, Darwin showed his specimens to fellow biologists and began writing up his travels.
It was then that he started to see how ‘transmutation’ happened.
He found that animals more suited to their environment survived longer and have more young.
Evolution occurred by a process he called ‘Natural Selection’ although he struggled with the idea because it contradicted his Christian world view.
Having experienced his grandfather being ostracised for his theories, Darwin collected more evidence, while documenting his travels, until 1851.
He decided to publish his theory after he began to suffer long bouts of sickness.
Some historians suggest that he had contracted a tropical illness while others felt that his symptoms were largely psychosomatic, brought on by anxiety.
In 1858, Darwin received a letter from Alfred Russel Wallace, an admirer of Darwin’s from reading about his Beagle Voyage.
Darwin drew fierce criticism from the Church and some of the press. Many people were shaken by the book’s key implication that human beings descended from apes, although Darwin only hinted at it
Wallace arrived at the theory of natural selection independently and wanted Darwin’s advice on how to publish.
In 1858, Darwin finally went public giving Wallace some credit for the idea.
Darwin’s ideas were presented to Britain’s leading Natural History body, the Linnean Society.
In 1859, he published his theory on evolution. It would become one of the most important books ever written.
Darwin drew fierce criticism from the Church and some of the press. Many people were shaken by the book’s key implication that human beings descended from apes, although Darwin only hinted at it.
In 1862, Darwin wrote a warning about close relatives having children, he was already worried about his own marriage, having married his cousin Emma and lost three of their children and nursed others through illness.
Darwin knew that orchids were less healthy when they self-fertilised and worried that inbreeding within his own family may have caused problems.
He worked until his death in 1882. Realising that his powers were fading, he described his local graveyard as ‘the sweetest place on Earth’.
He was buried at Westminster Abbey.
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