Migratory behaviour is positively associated with genetic diversity in butterflies

Migration is typically associated with risk and uncertainty, but little is known about its cost and benefit trade-offs. Migratory insects in particular often exhibit strong demographic fluctuations and cyclic outbreaks. Here, we explore the use of genomic demographic inference to investigate long-term population size dynamics in migratory insects, as an alternative to classical local and short-term approaches. We analyze genomic sequences from 60 Lepidoptera species and show that migratory species have significantly higher genomic heterozygosity, a proxy for effective population size, than non-migratory species. Also, we contribute whole-genome data for one of the most emblematic insect migratory species, the painted lady butterfly (Vanessa cardui), sampled across its cosmopolitan distribution range.