A new study by Monash University has shown that almost half of all insects native to the islands of the Southern Ocean have become flightless over time. On some of these remote islands, almost all insects have lost their ability to fly.
When the researchers examined the possible factors behind this inability to fly, they confirmed a 160-year-old theory by Charles Darwin that the inability to fly developed in response to wind.
“Of course, Charles Darwin knew about this wing loss habit of island insects,” said study director and PhD student Rachel Leihy.
“He and the famous botanist Joseph Hooker had a major argument about why this was happening. Darwin’s position was deceptively simple. If you fly, you will be blown into the sea. Those who stay on land to produce the next generation are the ones who fly the least, and eventually evolution does the rest. Voilà. “
Many scientists, including Hooker, questioned Darwin’s inability to fly theory, simply believing that he had misunderstood it. Most of these debates, however, have overlooked the sub-Antarctic islands where flight incapacity is most rapidly developed and these are some of the windiest places on earth.
“If Darwin really got it wrong, the wind would in no way explain why so many insects have lost their ability to fly on these islands,” Leihy said. The researchers set out to analyze every idea that was proposed to explain flight loss in insects.
“Terrestrial species on islands often have a reduced ability to spread. For insects, the general validity of the explanations for the island’s loss of flight remains controversial. While habitat stability is seen as the most plausible explanation, others are often highlighted, ”the study authors wrote. “We took a strong inference approach and examined the hypotheses proposed to explain the incapacity to fly prevalence in island insect clusters in a region long believed to be globally unusual in this regard – the Southern Ocean Islands (SOIs). ”
“By combining extensive animal inventories, morphological information on species and environmental variables from 28 SOI, we provide the first quantitative evidence that flightlessness is exceptionally common in native SOI insect species.”
The study showed that no idea other than Darwin’s wind theory could explain the extent of flight loss in sub-Antarctic insects.
“The results draw attention to Darwin’s wind hypothesis. However, they suggest that the wind selects inability to fly by making an energy compromise between flight and reproduction, rather than by moving it out of suitable habitats, ”the researchers explained.
Their results suggest that windy conditions make insect flight more difficult and energetically more expensive. As a result, insects no longer invest in flight and more in resources for survival and reproduction.
“It is noteworthy that after 160 years, Darwin’s ideas continue to provide insights into ecology,” said Leihy.
Study co-author, Professor Steven Chown, concluded that Antarctica is an exceptional laboratory for solving some of the world’s most persistent puzzles and testing some of its most important ideas.
The study is published in the journal Royal Society procedure B..
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By Chrissy Sexton, Earth.com Employed author
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