The synergistic impact of nitrogen deposition and heat stress on herbivorous insects: nettle-feeding Lepidoptera as model organisms

Globally, butterflies are among the best studied insects, and are often used as model organisms to study the effects of habitat loss, fragmentation, pollution and climate change. As severe declines in insect numbers are globally observed across various insect taxa, research is pointing out that the additive and synergistic effects of several, human-induced, environmental pressures could be the cause of this ‘insect Armageddon’. In this project, INBO will analyse synergistic effects of environmental pressures by testing to what degree different combinations of two stressors - nitrogen (N) enrichment and (micro)climatic change (e.g., heat stress) - are differently impacting four (formerly) common and widespread nettle-feeding butterfly species. To achieve this, INBO will analyse long-term monitoring data along a north-south gradient in Europe, link field nettle N-content with environmental variables, perform reciprocal transplant and multi-factorial common-garden lab experiments with offspring from differently-impacted populations, and measure proxies of larval and adult fitness. All in all, the combined experimental and correlative approaches will elucidate whether and to what degree adaptation to a changing environment is occurring. Ultimately, this research will show why these different species, although belonging to the same feeding guild, are differently impacted by a combination of global change drivers.