Phenotypic plasticity and associated costs in P. pacificus .

(A) The cost of plasticity in our model can be illustrated in a hypothetical scenario: The plastic strain expresses the defensive phenotype in the presence of predators (environment 1), but this plastic response to environment 1 is accompanied by a reduction in fitness, , which is the cost of plasticity. The fixed strain expresses the defensive phenotype regardless of the presence or the absence of predators. The production of the costly defensive phenotype in the absence of predators (environment 2), resulting in a relative cost of phenotypic mismatch between the fixed genotype and environment 2 () compared to the fitness of the plastic genotype in this environment. It is evident that costs of phenotype and plasticity are, by definition, exclusively meaningful in comparative studies in environments that can be described as adaptive and non-adaptive with regard to a given trait. The magnitude of the difference between and depends on the details of the machinery generating the plastic response, among other factors. Absolute value are used in this schematic figure to avoid any confusion with respect to the sign of these fitness differences. (B) The nematode P. pacificus expresses two alternative mouth forms, the predatory (eurystomatous) and the non-predatory (stenostomatous) from, in response to a variety of external stimuli. The fate of the mouth form is determined during post-embryonic development. (C) The effect of bacterial diet ( ϵ ) on the probability of developing the predatory mouth form in the plastic strain (λ P, ϵ ). The dotted gray line indicates the probability of developing the predatory mouth form in the non-plastic strain in both environments. The posterior distributions were generated by fitting a hierarchical bayesian model to laboratory measurements (For more information, see S1 Text and S1 Table ). (D) Growth on E. coli OP50 or Novosphingobium sp. L76 dramatically, and differentially, affects the number of eggs laid by the adult hermaphrodites belonging to the plastic or the non-plastic ...