Targeting the right trait: The relative suitability of a host plant depends on the herbivore trait considered and ambient temperature

Estimating the relative suitability of different host plant species for herbivores is usually based on survival and growth parameters, neglecting other parameters such as resistance traits. Adding further complexity, host plant suitability may depend on environmental temperature. We here use the oligophagous pierid butterfly Pieris napi to investigate effects of temperature (during both the larval and the adult stage) and larval host plant species (Alliaria petiolata, Cardamine pratensis and Sinapis alba) on life history and adult stress resistance traits (resistance to desiccation and starvation). Environmental temperature affected all developmental traits: at the lower temperature development time and body mass increased. Temperature also affected adult stress resistance: desiccation and starvation resistance were higher at the lower adult temperature. When the same temperatures were used during larval development, effects on adult stress resistance traits were in the opposite direction. Host plants affected life history (larger body mass and faster development in larvae fed S. alba) and stress resistance traits (best performance in larvae fed A. petiolata) differently. Thus, the relative suitability of a host plant depended on the trait of the herbivore that is focused on and may be subject to local selection pressures. Although interactions with temperature were present for all traits, effect sizes were generally small.