Effects of drought and infection on the development of the speckled wood butterfly

With global climate change, rainfall is becoming more variable. Predicting the responses of species to changing rainfall levels is difficult because, for example in herbivorous insect species, these effects may be mediated indirectly through changes in host plant quality. Furthermore, species responses may result from a simultaneous interaction between rainfall levels and other environmental stressors such as pathogen exposure. In line with predictions from life history theory, there is good evidence to suggest that deployment of the immune system is energetically costly and can result in trade-offs during the development of fitness-related traits such as; development time and pupal weight. In P. aegeria, growth on drought-stressed plants results in longer development times and smaller adult masses because of the low nitrogen, water and carbon content of leaves. As such, we hypothesised that growth on drought stressed host plants reduces a developing larva's capacity for effective immune function and results in trade-offs with fitness related traits.