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How Far the Butterfly Flies

Eastern and western monarch butterflies of North America are genetically similar, a new genomic analysis has found.

In eastern North America, monarch butterflies make long treks from their summer homes as far north as the US-Canadian border to their winter homes in Central Mexico, a flight that can be 3,000 miles long. West of the Rocky Mountains, monarch butterflies take a shorter trip of about 300 miles to California, suggesting that the two populations may be genetically distinct.

But in Molecular Ecology, researchers led by Emory University's Jacobus De Roode report on their analysis of 20 million SNPs in 43 monarch butterfly genomes. They instead found the two populations were genetically similar and the difference in their migration patterns may be due to environment-influenced changes in gene expression.

This, the researchers note in a statement, could be good news for monarch butterfly conservation efforts. "If environmental factors are all that drives the differences between the eastern and western monarchs, it's possible that we could help the western population by transplanting some of the eastern ones to the west," de Roode says in a statement.