Genetic and environmental sources of egg size, fecundity and body size (forewing length) were examined in the butterfly, Parnara guttata guttata. Phenotypic and genetic correlation and heritability were estimated for these traits under different day-length and temperature conditions. Egg size and fecundity had relatively high heritabilities, and body sizes in males and females had moderate and high heritability, respectively. Negative phenotypic and genetic correlations between egg size and fecundity were estimated in treatments corresponding to the natural conditions during larval development of the first and second generations. Phenotypic and genetic correlations between body size and egg size differed considerably between insects reared under long and short day-lengths. Next, genotype-environment interactions were estimated by comparing reaction norms to day-length or temperature of these traits among families. ANOVA analysis revealed significant genotype-environment interactions in egg size and forewing length in both sexes for day-length and temperature. These results suggested that a large additive genetic variance for egg size might have been maintained by a genetic trade-off and/or by genotype-environment interactions in P. g. guttata. © The Society of Population Ecology and Springer-Verlag 2006.

Egg size plasticity Genetic variation Genetic trade-off Genotype-environment interaction

heritability Insecta egg size butterfly genetic differentiation Hesperiidae Parnara guttata Lepidoptera Scomberesox saurus saurus larval development genotype-environment interaction fecundity body size Hexapoda phenotype