Ecological predictors of plant responses to sequential herbivory: a meta-analysis

Plants evolved alongside herbivores for over 400 million years and show remarkable plasticity in responses to attack by multiple herbivores. However, it is often debated which herbivore traits predict plant responses and it is poorly understood how plant life-history traits contribute to the variation observed in plant responses. We explored the role of ecological factors such as herbivore identity and plant life history by conducting a meta-analysis of 161 studies on the effects of sequential herbivory by arthropods, nematodes and mammals. We included herbivore performance and preference as measures of induced resistance and plant growth and damage as measures of plant performance. We uncovered that sequential herbivory reduced herbivore performance in most cases but did not consistently affect herbivore preference. Moreover, induced resistance was particularly observed in glasshouse experiments and in experiments on cultivated plant species. Plants managed to reduce plant damage but did not reduce biomass loss effectively. This study highlights that plants can effectively use induced responses to defend against sequential herbivore attack regardless of herbivore identity or plant life history. To elucidate the cost of multiherbivore attack and plant adaptations to these scenarios, there is a need to examine the consequences of the interactions on plant fitness.