A food-web model with stage-structured populations was built, and demography of persisted populations was investigated. The model consisted of consumers with three developmental stages (larvae, juveniles, and adults), which feed on unstructured primary producers exhibiting logistic growth and/or other consumers. Both feeding interaction and energetic processes were based on the body size of individuals associated with each stage (body size of a stage). The model was simulated starting with randomly selected body sizes and randomly selected initial densities, and this was repeated until five consumers persisted in the system over 2,000 time units. The simulations resulted in 106 food webs that had five persisting consumers. The life expectancy at birth, generation time, duration in an adult stage, average age at maturation, percent survival to an adult stage, and fecundity of persistent populations were calculated. Then, principal component analysis was applied to these demographic properties.
The first principal component (PC) was loaded high with duration in adult stage and generation time, indicating trade-off between semelparity and iteroparity. The second PC was loaded positively with percent mature and negatively with fecundity, indicating energetic trade-off between survival and reproduction during early stages. The third PC was loaded high with fecundity and the age of maturation, indicating the strategy to delay maturation to increase fecundity or vice versa. These life history properties represent commonly observed life history types in the natural aquatic systems. The result suggests that food web interactions are an important factor shaping the life history strategies of consumers.