Temperature and nutrient availability alter consequences of phenological shifts in predatory-prey communities

While there is mounting evidence indicating that the relative timing of
predator and prey phenologies shapes the outcome of trophic interactions,
we still lack a comprehensive understanding of how important the
environmental context (e.g. abiotic conditions) is for shaping this
relationship. Environmental conditions not only frequently drive shifts in
phenologies, but they can also affect the very same processes that mediate
the effects of phenological shifts on species interactions. Thus,
identifying how environmental conditions shape the effects of phenological
shifts is key to predict community dynamics across a heterogenous
landscape and how they will change with ongoing climate change in the
future. Here I tested how environmental conditions shape effects of
phenological shifts by experimentally manipulating temperature, nutrient
availability, and relative phenologies in two predator-prey freshwater
systems (mole salamander- bronze frog vs dragonfly larvae-leopard frog).
This allowed me to (1) isolate the effect of phenological shifts and
different environmental conditions, (2) determine how they interact, and
(3) how consistent these patterns are across different species and
environments. I found that delaying prey arrival dramatically increased
predation rates, but these effects were contingent on environmental
conditions and predator system. While both nutrient addition and warming
significantly enhanced the effect of arrival time, their effect was
qualitatively different: Nutrient addition enhanced the positive effect of
early arrival while warming enhanced the negative effect of arriving late.
Predator responses varied qualitatively across predator-prey systems. Only
in the system with strong gape-limitation were predators (salamanders)
significantly affected by prey arrival time and this effect varied with
environmental context. Correlations between predator and prey demographic
rates suggest that this was driven by shifts in initial predator-prey size
ratios and a positive feedback between size-specific predation rates and
predator growth rates. These results highlight the importance of
accounting for temporal and spatial correlation of local environmental
conditions and gape-limitation in predator-prey systems when predicting
the effects of phenological shifts and climate change on predator-prey
systems.