Associated costs and benefits of a defended phenotype across multiple environments

Summary 1. Many organisms respond to threats such as stress and predation by expressing a defended phenotype (phenotypic plasticity) or inducing the expression of a defended phenotype in offspring (transgenerational phenotypic plasticity). While defended phenotypes can increase resistance to a predator or stress, in the absence of the inducing agent defended phenotypes often have poorer performance. Producing a defended phenotype unnecessarily has been termed a phenotype-environment mismatch. 2. Most studies have focused on the benefits of a defended phenotype along a single environmental gradient (i.e. the presence/absence of the inducing agent) but in nature, organisms must face conditions that vary across a number of environmental gradients simultaneously. By focusing on the costs and benefits of a defended phenotype in a single dimension alone we risk underestimating the strength and likelihood of phenotype-environment mismatches. 3. For the marine bryozoan Bugula neritina, we examined the performance of individuals with an induced, defended phenotype (pollution resistance) relative to individuals with an undefended phenotype across a number of different environments. We found that individuals with the defended phenotype were more sensitive to osmotic stress, but surprisingly, were less susceptible to predation than individuals with the undefended phenotype. 4. Our findings suggest that the costs and benefits associated with expressing a defended phenotype are more complex than previously realized because the full consequences of induced phenotypes are only unmasked when performance in multiple environments is examined.