Researchers from the University of Georgia have discovered that monarch butterflies with extra white spots on their wings usually tend to full their long-distance migration to south and central Mexico.
Monarch butterflies with bigger white spots fly extra effectively, making lengthy journeys simpler.
A brand new examine examined almost 400 wild monarch wings and found that profitable migrant monarchs had about 3% much less black and three% extra white on their wings. The researchers hypothesize that the butterflies’ coloring is tied to the quantity of photo voltaic radiation they obtain throughout their migration, with the white spots enhancing their flight effectivity. However, with growing temperatures and modifications in photo voltaic radiation, these butterflies might should adapt to keep up their migration success.
If you’ve ever puzzled how the monarch butterfly acquired its spots, University of Georgia researchers might have simply discovered the reply.
The new examine means that the butterflies with extra white spots are extra profitable at reaching their long-distance wintering vacation spot. Although it’s not but clear how the spots help the species’ migration, it’s possible that the spots change airflow patterns around their wings.
“We undertook this project to learn how such a small animal can make such a successful long-distance flight,” said lead author Andy Davis, an assistant researcher in UGA’s Odum School of Ecology. “We actually went into this thinking that monarchs with more dark wings would be more successful at migrating because dark surfaces can improve flight efficiency. But we found the opposite.”
The monarchs with less black on their wings and more white spots were the ones that made it to their ultimate destination, nearly 3,000 miles away in south and central Mexico.
“It’s the white spots that seem to be the difference maker,” Davis said.
A University of Georgia study found that monarch butterflies with more white spots on their wings are more successful in their long-distance migration, likely due to improved flight efficiency through optimized solar energy absorption. However, climate change threatens this advantage, with higher solar intensity potentially reducing aerial efficiency.
Migration selects for butterfly spots
The researchers analyzed nearly 400 wild monarch wings collected at different stages of their journey, measuring their color proportions. They found that successful migrant monarchs had about 3% less black and 3% more white on their wings.
An additional analysis of museum specimens that included monarchs and six other butterfly species showed that the monarchs had significantly larger white spots than their nonmigratory cousins.
The only other species that came close to having the same proportion of white spots on its wing was its semi-migratory relative, the southern monarch.
Migratory monarchs have larger and more white spots than non-migratory relatives. Credit: Andrew K. Davis, using images courtesy of www.butterfliesofamerica.com with permission, CC-BY 4.0
Monarchs use solar energy to improve flight
The authors believe the butterflies’ coloring is related to the amount of radiation they receive during their journey. The monarchs’ longer journey means they’re exposed to more sunlight. As a result, they have evolved to have more white spots.
“The amount of solar energy monarchs are receiving along their journey is extreme, especially since they fly with their wings spread open most of the time,” Davis said. “After making this migration for thousands of years, they figured out a way to capitalize on that solar energy to improve their aerial efficiency.”
But as temperatures continue to rise and alter the solar radiation reaching Earth’s surface, monarchs will likely have to adapt to survive, said Mostafa Hassanalian, co-author of the study and an associate professor at the New Mexico Institute of Mining and Technology.
“With greater solar intensity, some of that aerial efficiency could go away,” Davis said. “That would be yet one more thing that is hindering the species’ fall migration to Mexico.”
Monarch breeding population is stable
But it’s not all bad news for the flying insects.
Davis’ previous work showed that summer populations of monarchs have remained relatively stable over the past 25 years. That finding suggests that the species’ population growth during the summer compensates for butterfly losses due to migration, winter weather and changing environmental factors.
“The breeding population of monarchs seems fairly stable, so the biggest hurdles that the monarch population faces are in reaching their winter destination,” Davis said. “This study allows us to further understand how monarchs are successful in reaching their destination.”
Reference: “How the monarch got its spots: Long-distance migration selects for larger white spots on monarch butterfly wings” by Andrew K. Davis, Brenden Herkenhoff, Christina Vu, Paola A. Barriga and Mostafa Hassanalian, 21 June 2023, PLOS ONE.
DOI: 10.1371/journal.pone.0286921
Published in PLOS ONE, the study was co-authored by Christina Vu, from UGA’s Odum School of Ecology, and Paola A. Barriga, from UGA’s Department of Plant Biology; and Brenden Herkenhoff, from New Mexico Tech.
