Each year, painted lady butterflies (Vanessa cardui) embark on amazing journeys, flying thousands of kilometers between Africa and Europe. They search for the best places to breed. A new study by researchers from the Institute of Science and Technology Austria suggests that the distance these butterflies travel is more about their environment than their genetics. This research, published in PNAS Nexus, shines a light on how certain factors influence insect migration.
The painted lady’s journey is a multi-generational migration. It starts in Northwest Africa, with butterflies crossing the Mediterranean into Europe. Later generations continue the journey north to places like Sweden as summer turns to autumn. Some butterflies might even travel all the way to sub-Saharan Africa, while others stay in the Mediterranean. It’s a fascinating cycle of travel and survival.
To better understand what influences these migratory patterns, researchers collected butterflies from several countries, including Benin, Senegal, Morocco, Spain, Portugal, and Malta. They used a technique known as isotope analysis to trace where each butterfly originated. This method uncovered a range of migratory behaviors among these insects.
Isotope analysis connects a butterfly’s isotopic composition to the environment where it grew up. The wings of a butterfly retain the isotopic signature of the plants it ate as a caterpillar, which helps scientists figure out its birthplace.
Interestingly, some butterflies soared across the Sahara, while others preferred the Mediterranean shores. When scientists looked at the butterflies’ genomes, they found no significant genetic differences between those that traveled long distances and those that did not.
So, what guides the painted lady butterflies in their migration? Unlike some birds, whose genes dictate their travel paths, these butterflies seem to respond to environmental signals. The researchers point to something called phenotypic plasticity—the ability to change behavior based on the surroundings—as a crucial factor.
Phenotypic plasticity means the butterflies can adjust how they act or when they travel without changing their genetic make-up. For example, as days shorten in Sweden at summer’s end, butterflies may feel the urge to migrate southward. In contrast, butterflies in warmer regions may not experience the same urgency, leading them to travel shorter distances.
There’s still much to learn about painted lady migrations, especially when compared to better-understood species like monarch butterflies. Future research may reveal whether these discoverable patterns apply to more painted lady populations or to other insects with complex migratory behaviors.
This new understanding of painted lady butterflies not only enriches our knowledge of migration but also highlights the intricate connections these insects have with their environments.
Reference: Reich MS, Shipilina D, Talla V, et al. Isotope geolocation and population genomics in Vanessa cardui: Short- and long-distance migrants are genetically undifferentiated. PNAS Nexus. 2025;4(2):pgae586. doi: 10.1093/pnasnexus/pgae586
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