University of Guelph researchers have pinpointed the North American birthplaces of migratory Monarch butterflies that overwinter in Mexico by analyzing “chemical fingerprints” in the wings of butterflies collected as far back as the mid-1970s.
The largest percentage of Monarchs migrated to Mexico from the American Midwest, but the biologists were surprised to find that the insects’ origins were spread fairly evenly throughout Canada and the United States.
“We expected the vast majority of Monarch butterflies to be found in the Midwestern states,” said Tyler Flockhart, lead author and Liber Ero postdoctoral fellow at the University of Guelph. “However, just 38% come from that part of the U.S. If we just focus conservation activities on this area, this research shows we will be missing a large number of butterflies born elsewhere in North America.”
This is the first detailed look at where overwintering Monarch butterflies are born over multiple years, he said.
Monarch numbers have dropped significantly in recent years, likely due partly to the control of milkweed, regarded as a weed pest in agricultural fields. Monarchs feed on milkweed and lay their eggs on the plants.
Analyzing more than 1,000 samples, the research team looked at chemical isotope signatures showing where the butterflies were born in the previous summer and fall. They found that 12% of the insects were born in the northwestern U.S. and Canadian prairies, 17% in the north-central states and Ontario, 15% in the northeastern U.S. and the Maritimes, 11% in the south-central U.S. and 8% in the southeastern tates.
Midwestern habitat conservation is a priority, but the authors note that effective conservation calls for efforts across the entire species range.
The Guelph researchers worked with collaborators at Western University, London, Ontario; the University of Georgia; Sweet Briar College; Universidad Nacional Autonoma de Mexico; Environment Canada and the International Atomic Energy Agency.
February 1, 2017 NewTerrain