Altered rainfall patterns reduce plant fitness and disrupt interactions between below- and aboveground insect herbivores

Abstract

Evidence is accumulating of the disruptive effects of climate change on species interactions. However, little is known about how changes in climate patterns, such as temporal shifts in rainfall events, will affect multitrophic interactions. Here, we investigated the effects of changes in rainfall patterns on the interactions between root herbivores, a plant, and its associated aboveground insects in a semiarid region by experimentally manipulating in the field rainfall intensity and frequency. We found that a shift in rainfall severely constrained biomass acquisition and flowering of the plant Moricandia moricandioides, resulting in fitness reduction. Importantly, enhanced rainfall affected the interactions between below- and some aboveground herbivores, disrupting the positive effects of root herbivores on chewing insects. The shifts in precipitation had also plant-mediated consequences for planthoppers, the dominant sapsuckers in our study system. A combination of mechanisms involving biomass acquisition and plant defenses seemed to be responsible for the different responses of insects and their interactions with the plant. This study provides evidence that altered rainfall patterns due to climate change affect not only trophic groups differentially but also their interactions.