Large-scale whole-genome sequencing of migratory Bogong moths Agrotis infusa reveals genetic variants associated with migratory direction in a panmictic population.

One of the most interesting macroscopic phenomena in the animal world is seasonal migration. A central goal of research into animal migration is to better understand the mechanisms that evolved to solve the complex challenges which a migratory life history presents. Each year, and with a high degree of species-level site fidelity, the Australian Bogong moth makes a return migration of up to and over 1000 km between widely distributed breeding grounds and a specific set of aestivation sites in the Australian Alps. It does this without any opportunity to learn the migratory route or the location of the aestivation sites from either older generations or repeated migrations, meaning that the information required by the moth to navigate during its migration must be inherited. The migratory direction, and therefore the inherited navigational information in Bogong moths, varies with breeding site, providing us with an opportunity to search for the source of that heritability by comparing the genomes of moths collected from different breeding areas. We successfully sequenced whole nuclear genomes of 77 Bogong moths collected from across their breeding grounds and summer range, and found that the Bogong moth population contains a large amount of (mostly rare) variation. We found no evidence of population structure, indicating that Bogong moths are panmictic. A genome-wide scan for signals of selection indicate that the Bogong population has recently recovered from a past bottleneck, however genomic regions which have likely undergone balancing selection were also detected. Despite panmixia, four genetic variants in breeding-ground-caught Bogong moths were found to be significantly associated with geographic location, and therefore migratory direction, indicating promising future avenues of research into the molecular basis of long-distance navigation.