Consequences of shifts in the mean and variation in prey phenology for predator-prey interactions
Most habitats exhibit seasonal changes in environmental conditions. These seasonal patterns can vary among years, which can alter the timing of the seasonal life-history events, or phenologies, of species. Co-occurring species oftentimes differ in their phenological response to year-specific conditions, which could alter the stage at which species interact. However, we do not have a good understanding of how these changes in phenology affect the outcome of interactions. In this study, we determined how variation in two aspects of the phenological distribution of a prey species affects the outcome of predator-prey interactions. Specifically, we used a factorial design to manipulate the mean and the amount of variation around the mean (i.e., degree of synchrony) of tadpole hatching in the presence of a dragonfly nymph predator.
We found that the effects of mean and synchrony of hatching on prey survival were additive, with survival declining with later hatching and lower hatching synchrony. As survival declined, this generally led to faster growth rates for surviving tadpoles. Therefore, prey phenological variation can affect the number of offspring that survive to recruit into the adult population and time at which this occurs, both of which have implications for prey demographic rates. Despite these effects on the prey, there were no effects on survival or growth of the predator, indicating that prey phenological timing has stronger implications for prey than predators. If these results are general, it indicates that we can understand the effects of multiple types of phenological variation by summing their individual effects, but additional studies are needed to confirm this. Determining the consequences of phenological variation for species interactions is important for understanding seasonal communities as well as how these communities will be affected by climate change.