Selection for larval growth inTriboliumunder two levels of nutrition

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Abstract
Selection for large and small 13-day larval weight inTribolium castaneumwas studied for sixteen generations in a replicated experiment to evaluate the effectiveness of various selection methods and the importance of genotype by environment interactions under two levels of nutrition.Direct selection responses generally were larger than correlated ones under both Good and Poor nutritional environments. However, contrary to theoretical expectations, those populations selected on average performance in both environments were not superior for this attribute.Asymmetrical responses were observed to be dependent on the environment of selection. When selection was based on performance in the optimal environment, the asymmetry was observed toward small size. This situation in the sub – optimal environment was completely reversed. This phenomenon was discussed in terms of physiological limits rather than gene frequency and directional dominance.It was proposed that selection of compound traits such as body weight at a fixed age may affect the component characters quite differently. As the latter are differentiated by direction and environment of selection, the compound trait may reflect parametric changes and enhanced genotype by environment interactions. Such changes hamper the precision of current selection theory for predicting response even in the short run.