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Butterfly Migration
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Shipilina and her team studied the migration of painted lady butterflies (Vanessa cardui) to determine if there are genetic differences between short- and long-distance migrants.
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- The study involved researchers from Austria, Benin, Canada, Senegal, Spain, and Sweden.
- Findings published in the journal PNAS Nexus showed that migration distances were influenced more by environmental factors than genetics.
- Unlike birds, painted lady butterflies do not have significant genetic differences between short- and long-distance migrants.
Challenges in Studying Insect Migration
- Studying insect migration has been historically difficult due to their small size and lack of effective tracking technologies.
- Recent advancements in genomics and miniaturised tracking tools have enabled precise research on insect migration patterns.
Key Findings of the Study
- Short- and long-distance migrating painted ladies belong to a single interbreeding population, without distinct genetic groups.
- Wing size and shape did not significantly impact migration distance.
- Higher wing-wear did not necessarily indicate longer migration distances; some butterflies that travelled 4,000 km had minimal wing-wear.
Understanding Phenotypic Variations in Organisms
- Phenotypes include physical, biological, or behavioural traits influenced by genetics and environmental factors.
- Examples include skin and hair colour in humans, vocal behaviour in birds, and migratory patterns in animals.
- Migration is a complex phenotype influenced by multiple factors like timing, orientation, distance, and wing shape.
Unique Migration Patterns of Painted Lady Butterflies
- Painted lady butterflies are found on every continent except Antarctica and South America.
- They thrive in diverse climates, from temperate grasslands to deserts.
- They undertake one of the longest insect migrations, travelling up to 15,000 km in a single migratory cycle.
- Their migration follows a multi-generational cycle, spanning 8–10 generations, with each butterfly living only 2–4 weeks.
- Unlike birds, they do not return to the same breeding grounds, making their migration a “family business.”
Tracking Butterfly Migration Across Continents
- The research team observed butterflies in Benin, Senegal, Morocco, Spain, Portugal, and Malta.
- In spring, painted ladies migrate north from the Sahara Desert, crossing the Mediterranean to breed in southern Europe.
- By late summer and autumn, their offspring return south across Spain and Italy to North Africa.
- Painted ladies have strong thoracic muscles adapted for long-distance flight.
Isotopic Analysis to Determine Origins
- Butterfly wings retain stable isotopes of hydrogen and strontium from food and water consumed as larvae.
- Since wings are metabolically inactive, they preserve the isotopic signature of their birthplace.
- Researchers analysed isotope ratios in butterfly wings to determine their regions of origin.
- European and North African isotope maps (isoscapes) were used to estimate the distances covered by each butterfly.
Future Research Direction
- Researchers plan to study genetic differences in painted ladies from distant regions such as the UK and Japan.
- Further investigations will examine how migration patterns change in different environmental conditions.
- The study contributes to understanding how environmental factors shape insect migration and potential shifts due to climate change.
- Shipilina believes insect migration may differ significantly from bird migration and hopes comparative studies will reveal key similarities and differences.
