Complex multi-trait responses to multivariate environmental cues in a seasonal butterfly

Many organisms inhabiting seasonal environments exhibit adaptive developmental plasticity, allowing them to optimally match life-history traits with fluctuating conditions. This critically relies on environmental cues, such as temperature, as predictors for seasonal transitions. In most seasonal environments, multiple factors vary together, but might not be equally relevant as cue, making it crucial to understand their combined effects on an organism’s phenotype. Here, we study plasticity in a multivariate environment in the seasonally polyphenic butterfly Bicyclus anynana. Using a full-factorial design, we test how developmental temperature and host plant quality interact to affect life-history traits. Our results show that the cues interact: reduced food quality can act as a predictive cue at temperatures normally associated with the food-rich wet season, inducing a partial dry season phenotype. At low temperatures, normally associated with the food-poor dry season, reduced food quality had an adverse effect on life history, with decreased body mass and prolonged development time. However, metabolic rates in adults were not affected, indicating that individuals could partly compensate for stressful juvenile conditions. Thus, under certain environmental conditions, a single cue (e.g. temperature) might suffice to shape an organisms’ phenotype, while under other conditions additional cues (like plant quality) might be needed in shaping the organism’s phenotype to optimally match seasonal conditions. Our study reveals complex interactive effects of two environmental variables on seasonal plasticity, highlighting the importance of studying multivariate environmental factors to better understand the regulation of phenotypic plasticity in the wild.