Complex patterns of phenotypic plasticity: Interactive effects of temperature during rearing and oviposition

Temperature profoundly affects growth and life history traits in ectothermic animals through selection (i.e., genetic) and through direct effects on the phenotype (i.e., nongenetic/plasticity). We examined the effects of rearing temperature (24°, 30°, and 36°C) on adult body size and development time and the interactive effects of temperature experienced during rearing and oviposition on several life history traits (age-at-first- reproduction, fecundity, egg size, egg development, and egg hatching) in two populations of the seed beetle, Stator limbatus, collected at different elevations. The higher elevation population was larger and matured sooner than the low-elevation population when raised at the lower temperature, but the reverse was true at the higher temperature suggesting that these populations have adapted to local temperature. There were interactions between the effects of rearing temperature and oviposition temperature for age-at-first- reproduction, fecundity, egg development, egg hatching, and two composite measures of fitness, generating complex reaction norms. The most dramatic example of this was a large maternal effect on egg hatching; females raised at low temperature produced eggs that had substantially reduced hatching when laid at high temperature. Our experimental design also allowed us to explore the adaptive significance of acclimation. Beetles reared at intermediate or low temperature had the highest fitness at multiple oviposition temperatures. There was little support for the "beneficial acclimation hypothesis," which predicts that beetles should have higher fitness at the temperature at which they were reared; acclimation had only a small effect on fitness. This study shows that temperature-mediated plasticity can be complex, but these complex patterns can yield new insights into the evolution of phenotypic plasticity.