Wolbachiainfection negatively impactsDrosophila simulansheat tolerance in a strain- and trait-specific manner

Abstract

AbstractThe susceptibility of insects to rising temperatures has largely been measured by their ability to survive thermal extremes. However, until recently, the capacity for maternally inherited endosymbionts to influence insect heat tolerance has been overlooked. Further, the impact of heat on traits like fertility, which can decline at temperatures below the lethal thermal limit has largely been ignored. Here, we assess the impact of threeWolbachiastrains (wRi,wAu, andwNo) on the survival and fertility ofDrosophila simulansexposed to heat stress during development or as adults. The impact ofWolbachiainfection on heat tolerance was generally small and trait/strain specific. Only thewNo infection significantly reduced survival and fertility of adult males after a heat shock. When exposed to a fluctuating heat stress during development, thewRi andwAu strains reduced egg-to-adult survival but only thewNo infection reduced male fertility.Wolbachiadensities of all three strains decreased under developmental heat stress, but reductions occurred at temperatures above those that reduced fertility of the host. These findings reveal the complexity of endosymbiont-host-environment interactions and emphasise the necessity to account for endosymbionts and their effect on both survival and fertility when investigating the vulnerability of insects to climate change.