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Gene aids butterfly disguise

A single gene controls all the colors, structures and wing patterns in a species of swallowtail butterfly, researchers say – allowing it to mimic the look of another swallowtail that is toxic to predators.

“Everything traces back to this one gene,” said one of the scientists, Marcus Kronforst, an evolutionary biologist at the University of Chicago.

The finding, reported in the journal Nature, was surprising, since the gene, called doublesex, is known for its role in sexual differentiation in insects. In this role, the gene is responsible for informing every cell in an insect’s body whether it is male or female.

Female Papilio polytes swallowtails have one of four wing patterns, three of which mimic the look of different toxic butterflies. While flying, the females become indistinguishable from their toxic counterparts.

To identify the gene responsible for regulating wing patterns, the researchers mated swallowtails with different patterns and compared the genomes of the offspring, then isolated genes that might be involved in mimicry.

They were expecting to find a supergene – multiple, tightly linked genes working together. Instead, they found that only one, doublesex, is responsible for mimicry.

Chickadee zone surges north

In a long, narrow strip of territory from Kansas to New Jersey, two closely related species of chickadees meet, mate and give birth to hybrid birds. Now scientists are reporting that this hybrid zone is moving north at a rate that matches the warming trend in winter temperatures.

“It has moved north by about 7 miles in the last 10 years,” said Scott Taylor, an evolutionary biologist at the Cornell Lab of Ornithology at Cornell University.

The northward movement of the strip “corresponds so closely to warming global temperatures,” Taylor said. “The fact that these little birds are experiencing this makes it really relatable.” (The species are the Carolina chickadee, from the South, and the black-capped chickadee, from the North.)

The scientists, who reported their findings in the journal Current Biology, relied on blood samples drawn from chickadees in Pennsylvania from 2000 to 2002 and from 2010 to 2012, and on sightings of hybrid chickadees recorded in the citizen science database eBird. They found that hybrids were sighted in areas where the average low temperature in winter was 15 to 19 degrees Fahrenheit – the same readings as a decade earlier, but in a zone 7 miles north of the 2000-02 sightings.

– New York Times