Power Behind Monarch Butterfly Migration Lies in a Single Gene

After sequencing 101 butterfly genomes, scientists have found that the power behind monarch migration lies in a single gene, a new study describes.

This iconic insect, known for its distinctive black and orange coloring, migrates en masse across North America each year, from as far north as Canada down to Mexico. The new genetic analysis, published in the journal Nature, includes some surprising findings about monarch butterflies.

For one, it appears as if the ancestors of modern-day monarchs initially dispersed out of North America - rather than Central or South America, as previously thought. In addition, a single gene appears to play a key role in giving monarchs their striking coloration.

"The results of this study shift our whole thinking about these butterflies," study senior author Marcus Kronforst, from the University of Chicago, said in a statement.

To unravel the full story, Kronforst and his team sampled 101 butterflies, including both migratory and non-migratory monarchs. Out of the 500 genes identified, one in particular, known as Collagen IV alpha-1, displayed some notable differences between the migratory and non-migratory butterflies. Further investigation suggested that the gene played a role in building muscle tissue, giving migratory monarchs a more efficient metabolism than non-migratory monarchs so that they could fly such far distances.

"This increase in metabolic efficiency seems to be the result of flight muscle performance, because the difference between migratory and non-migratory populations was minimal when not in flight," the researchers wrote.

The other big genetic finding has to do with the monarch's famous coloration. Some monarchs in Hawaii lack the orange and black colors, instead sporting black and white wings. When the researchers analyzed the genetic differences between the two varieties, they discovered that a myosin gene, which also plays a key role in the color of a mouse's furry coat, was strongly associated with monarch wing color.

Today, these colorful, migrating monarch butterflies are facing a devastating decline, due to factors ranging from deforestation and drought to a drastic decline in milkweed, their main food source. They recently became a protected species under the Endangered Species Act after it was found that the species has declined more than 90 percent since 1990.

"We are seeing possibly the tail end of this phenomenon of migration," Kronforst told NBC News. "To me, it adds a sad exclamation point to the story."