Phenotypic plasticity and fitness in egg parasitoids

Several proxies can be used to estimate the fitness of egg parasitoids: size, longevity, fecundity, mating ability and vagility. All these proxies are positively correlated with the lifetime fitness gain of an individual. However, the phenotypic plasticity, which is the ability of a genotype to produce distinct phenotypes depending on environmental conditions, may alter the value of these proxies. Host related factors (host species and quality), competition and duration of development will influence the proxies expressed by a given phenotype. When the phenotype is modified by the temperature at which an individual develops, the resulting phenotype will vary based on the life history strategy of the parasitoid. While in koinobiont species an increase in size is positively correlated with longevity and fecundity, the reverse occurs with idiobiont parasitoids. Using size as a proxy could thus be misleading depending on the factors that influence the size of the adult.