Samoa butterflies quickly evolve and avoid extinction
In 2001, male Hypolimnas bolina butterflies on the Samoan islands of Savaii and Upolu were extremely rare. Just 1 percent of these butterflies — known commonly as Blue Moon or Great Eggfly — were male. They were under attack by the Wolbachia bacteria, a parasite passed down through the female that kills off male butterflies before they can hatch.
Last year, the numbers of males had either reached or were approaching those of females. They were helped by the development of a genetic mutation that suppresses the bacteria, sparing the males and allowing them to quickly repopulate.
“This is one of the most clear and fastest cases of evolution under natural selection,” said Sylvain Charlat of University College London, whose study appears in the journal Science.
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