Meeting Abstract
Phenotypic plasticity is often an adaptation to varying environments but two inescapable features on environments and organisms may limit the adaptive significance of plasticity. First, environments vary in multiple and less-than-perfectly correlated ways meaning that an optimal response to one variable factor may result in less-than-optimal responses to another. Second, the integrated nature of organisms means that very often plasticity in one trait is not independent of plasticity of others; this, too, can limit optimal phenotypic plasticity. Our understanding of the limits of adaptive plasticity therefore depends upon studies that investigate multiple interacting environmental factors and the plasticity of multiple traits. The plastic wing pattern of the cabbage white butterfly serves as an ideal model for such an investigation because wing pattern elements vary in complex and in seasonally predictable ways. We examined the causes of wing pattern plasticity by experimentally manipulating temperature, photoperiod and dietary nutrients and find that all factors can, at least under some factor combinations, affect wing pattern elements. Furthermore, we find that in addition to these interactive effects, different wing pattern elements respond to environmental variation in different ways. Increased temperature increases the size of some wing pattern elements while decreasing the size of others. Photoperiodic variation also affected wing pattern, though to a lesser degree. Both temperature and photoperiod produced complex reactions norms for some wing pattern elements. Nutrient effects were relatively minor. Our results highlight the importance of including multiple environmental factors and multiple traits in studies of adaptive plasticity.
