The importance of quantifying selection climates: predictable and unpredictable variation in predation risk and the...

Prey behavioural traits within a population are commonly variable, unexpectedly so, given that predation is thought to be a strong selection pressure. This variation likely arises from complex, variable selection pressures, but experimental evaluations of prey responses to natural variability in selection pressures remain limited. We focus on the rock-pool-breeding mosquito Aedes vexans, which can influence the predation risk to its offspring through site selection for oviposition. We quantified the nature of selection pressures in the wild, i.e. the spatial and temporal variation in larval predation risk, by measuring densities of predatory dragonfly nymphs in rock pools along the mosquito breeding season. To examine the implication of selection pressure regimes for the evolution of oviposition site selection, we conducted manipulative experiments and measured female oviposition responses to variation in predation risk. Predation risk varied extensively over space and time; this variation showed both predictable and unpredictable elements. Females avoided large pools with permanent predators but appeared to show variable responses to medium-sized pools with unpredictable predation risk. We suggest that while it might be challenging to quantify complex selection environments and their impact on wild prey responses, more such studies can help explain puzzling variation in anti-predator responses.