EFFECTS OF TEMPERATURE AND DIETARY NITROGEN ON GENETIC VARIATION AND COVARIATION IN GYPSY MOTH LARVAL PERFORMANCE TRAITS

To assess the plastic and genetic components of variation in responses of gypsy moth (Lymantria dispar) 4th instar larvae to temperature and food quality, we applied a split-family four-environment experimental design where full-sibs were reared on two constant temperatures (23 degrees C and 28 degrees C) and two concentrations of dietary nitrogen (1.5 and 3.7% dry weight). A temperature of 28 degrees C and low dietary nitrogen decreased larval weight and prolonged larval developmental time, while viability was not affected. Only a marginally significant interaction between the two environmental factors was found for larval weight. The broad-sense heritability for larval developmental time did not change across environments, and across-environment genetic correlations were close to one. Heritability for larval weight depended on environmental and across-environmental genetic correlations that were not significant. There was no evidence of a trade-off between developmental time and larval weight. The implications of the obtained results for the evolution of phenotypic plasticity in complex environments are discussed.