Fight or flight? - Flight increases immune gene expression but does not help to fight an infection

Flight represents a key trait in most insects, being energetically extremely demanding, yet often necessary for foraging and reproduction. Additionally, dispersal via flight is especially important for species living in fragmented landscapes. Even though, based on life-history theory, a negative relationship may be expected between flight and immunity, a number of previous studies have indicated flight to induce an increased immune response. In this study, we assessed whether induced immunity (i.e. immune gene expression) in response to 15min forced flight treatment impacts individual survival of bacterial infection in the Glanville fritillary butterfly (Melitaea cinxia). We were able to confirm previous findings of flight induced immune gene expression, but still observed substantially stronger effects on both gene expression levels and lifespan due to bacterial infection compared to flight treatment. Even though gene expression levels of some immunity-related genes were elevated due t...