Researchers sequenced the genome of the monarch butterfly and found a specific gene they believe is central to migration and another that is responsible for pigmentation.
Monarchs embark on a mass migration from Canada to Mexico every year, but their numbers are dramatically declining, the University of Chicago Medical Center reported.
"The results of this study shift our whole thinking about these butterflies," said study senior author Marcus Kronforst, Neubauer Family Assistant Professor of Ecology and Evolution at the University of Chicago.
To make their findings the researchers compared the genomes of 101 butterflies including migratory North American monarchs, non-migratory monarchs, and a few other species. They identified more than 500 genes and noticed an interesting disparity. The researchers found migratory monarchs consumed less oxygen and had lower flight metabolic rates, which most likely supports their ability to fly long distances.
"Migration is regarded as a complex behavior, but every time that the butterflies have lost migration, they change in exactly the same way, in this one gene involved in flight muscle efficiency," Kronforst said. "In populations that have lost migration, efficiency goes down, suggesting there is a benefit to flying fast and hard when they don't need to migrate."
The team also investigated the butterflies' coloration. A small percentage of monarchs, mostly located in Hawaii, have red and white wings. The researchers pinpointed a single gene responsible for this pigmentation switch.
The findings provide a new genetic pathway affecting insect color to explore as well as the origin of migration. Migratory monarchs are believed to have started out in the southern U.S. or Mexico. When three separate branches migrated to Central and South America; across the Atlantic; and across the Pacific these butterflies lost their migratory tendencies.
The findings of this study emphasize the need to preserve monarch migration in order to extend their evolutionary history.
"You used to see huge numbers of monarchs, clouds of them passing by," Kronforst said. "Now it looks quite possible that in the not too distant future, this annual migration won't happen."
The findings were published Oct. 1 in the journal Nature.
