Abstract

Among movement strategies, migratory behavior is particularly intriguing in insects. Home-breeding is often permanent, and return journeys can take several generations. Although migration is crucial to the ecological and evolutionary processes of the species involved, knowledge of insect migratory behavior needs to be better understood. Vanessa carye, a butterfly native to South America with a latitudinal range of ?7,000?km, exemplifies this problem. This study analyzed samples collected across the species' range using single-nucleotide polymorphisms (SNPs) to assess population structure, genetic diversity, and geometric morphometrics to examine wing shape variation. Results indicate that V. carye forms a genetically homogeneous unit composed of only two potential populations spanning ?5,000?km, geographically correlated with the Pacific Ocean and the Andes, maintaining constant gene flow, and with a mean heterozygosity of 5.74% (SE: ±0.048%). Geometric morphometrics detected no geographic differentiation in wing shapes and sizes across ?7,000?km, suggesting an absence of local adaptation and indicating a conserved wing shape adapted to flight throughout the species' range. Our findings support V. carye as a migratory species with the longest migratory journey among American butterflies, revealing two migratory routes. With these approaches, we provide a consistent methodological framework for migratory studies in species with important gaps in knowledge of their natural history. © 2025 The Author(s).