To fool predators, some butterflies create wing color patterns that make them resemble their unpalatable cousins. Only recently have scientists been unraveling how they do that, and now researchers have identified the gene that does the trick for an Asian swallowtail.
In fact, it's a surprise that just one gene can let females of the species, sometimes called the common mormon, produce the elaborate wing markings of toxic relatives. Scientists had proposed that it would take a cluster of genes.
"We were very shocked when we found it was just the one," said Marcus Kronforst of the University of Chicago, senior author of the study published online Wednesday by the journal Nature.
The gene was already known to play a different role, basically telling body cells whether the insect is male or female. It was apparently co-opted to take on the second job of controlling wing patterns in females, Kronforst said.
The gene acts as a switch, regulating other genes to produce wing patterns that mimic those of any of three species of toxic butterflies. A given butterfly's pattern depends on what versions of the gene it inherited from each parent. The gene can also make a female's wing look like a male's.