Stressing food plants by altering water availability affects grasshopper performance

Extreme weather events like drought and heavy rain are likely to increase with climate change in Central Europe and may affect nutrient content in plants. They may therefore influence the performance (growth rate, developmental time, mortality, body size/mass, fecundity) and population dynamics of herbivorous insects. We conducted a common-garden experiment on food plants to investigate effects of severe drought and moisture events on reproduction and fitness components in the insect herbivore Chorthippus biguttulus (Orthoptera, Acrididae). Periodic irrigations of food plants were used to simulate a 60% decrease in average summer precipitation (drought treatment), a 40% increase in average summer precipitation (moisture treatment) and a normal summer precipitation (control treatment). Individuals of C. biguttulus that fed on drought-stressed plants showed beneficial effects on life-history traits including an increased reproductive success than grasshoppers that fed on control plants. The opposite was true for individuals feeding on plants grown under severe moisture conditions. We propose that herbivore performance is influenced by increased concentrations of soluble proteins and amino acids in plants under drought stress conditions. Our results suggest that drought events may increase population performance and consequently population density in the grasshopper species C. biguttulus, while extreme moisture events may cause negative population trends.