Does increased heat resistance result in higher susceptibility to predation? A test using (Drosophila melanogaster) selection and hardening

Heat resistance of ectotherms can be increased both by plasticity and evolution, but these effects may have trade-offs resulting from biotic interactions. Here we test for predation costs in Drosophila melanogaster populations with altered heat resistance produced by adult hardening and directional selection for increased heat resistance. In addition, we also tested for genetic trade-offs by testing heat resistance in lines that have evolved under increased predation risk. We show that while 35/37°C hardening increases heat resistance as expected, it does not increase predation risk from jumping spiders or mantids; in fact there was an indication that survival may have increased under predation following a triple 37°C compared to a single 35°C hardening treatment. Flies that survived a 39°C selection cycle showed lower survival under predation, suggesting a predation cost of exposure to a more severe heat stress. There was however no correlated response to selection because survival did...