The importance of quantifying selection climates: Predictable and unpredictable variation in predation risk and the implications for prey responses

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 appear 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.