WASHINGTON – The masquerade party never ends for these ladies.
The females of an Asian swallowtail butterfly species known as the common Mormon often mimic the appearance of another species of butterfly that is toxic for predators to eat, with strikingly similar coloration and markings on the wings.
The evolutionary skullduggery tricks birds that otherwise would be happy to munch these insects into keeping them off the menu, thinking they are inedible.
Scientists long have studied this type of mimicry in nature and pondered the biological mechanisms behind it.
In the case of the masquerading common Mormon, the researchers led by Marcus Kronforst, a professor of ecology and evolution at the University of Chicago, said Wednesday they have identified the gene responsible.
It is a gene called “doublesex” that already was known to control the development sex-specific attributes in insects.
Kronforst said many experts had assumed that something as complex as this mimicry would be controlled by multiple genes. “We, in fact, find that it’s just one gene,” said Kronforst, whose findings were published in the journal Nature.
The impostor butterflies are engaging in what is known as “Batesian mimicry,” named after 19th century naturalist Henry Walter Bates, who first described it after studying butterflies in South America. Charles Darwin’s theory of natural selection helped guide Bates’ observations.
“Batesian mimicry is the amazing phenomenon where a perfectly harmless creature resembles a dangerous, noxious or poisonous species,” said Sean Carroll, a professor of molecular biology and genetics at the University of Wisconsin. “It was a very important discovery because it was obvious evidence for natural selection — the harmless species gains an advantage by resembling something predators avoid — right after the publication of Darwin’s theory.”
There are numerous examples of such mimicry in nature.
The common Mormon butterfly, whose scientific name is Papilio polytes, is widely distributed throughout South and Southeast Asia. Males do not mimic the appearance of other species, but many females do.
Four different wing patterns appear. One resembles that of the male of the species. The other three mimic the wing pattern of three awful-tasting species.
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