Data from: Plant resistance reduces the strength of consumptive and non-consumptive effects of predators on aphids

1. The impact of predators on prey has traditionally been attributed to
the act of consumption. Prey responses to the presence of the predator
(non-consumptive effects), however, can be as important as predation
itself. While plant defences are known to influence predator–prey
interactions, their relative effects on consumptive vs. non-consumptive
effects are not well understood. 2. We evaluated the consequences of plant
resistance and predators (Hippodamia convergens) on the mass, number of
nymphs, population growth, density and dispersal of aphids (Macrosiphum
euphorbiae). We tested for the effects of plant resistance on
non-consumptive and consumptive effects of predators on aphid performance
and dispersal using a combination of path analysis and experimental
manipulation of predation risk. 3. We manipulated plant resistance using
genetically modified lines of tomato (Solanum lycopersicum) that vary
incrementally in the expression of the jasmonate pathway, which mediates
induced resistance to insects and manipulated aphid exposure to lethal and
risk predators. Predation risk predators had mandibles impaired to prevent
killing. 4. Plant resistance reduced predation rate (consumptive effect)
on high resistance plants. As a consequence, predators had no impact on
the number of nymphs, aphid density or population growth on high
resistance plants, whereas on low resistance plants, predators reduced
aphid density by 35% and population growth by 86%. Path analysis and
direct manipulation of predation risk showed that predation risk rather
than predation rate promoted aphid dispersal and varied with host plant
resistance. Aphid dispersal in response to predation risk was greater on
low compared to high resistance plants. The predation risk experiment also
showed that the number of aphid nymphs increased in the presence of risk
predators but did not translate into increased population growth. 5. In
conclusion, the consumptive and non-consumptive components of predators
affect different aspects of prey demography, acting together to shape prey
population dynamics. While predation risk accounts for most of the total
effect of the predator on aphid dispersal and number of nymphs, the
suppressive effect of predators on aphid population occurred largely
through consumption. These effects are strongly influenced by plant
resistance levels, suggesting that they are context dependent.