Long -term selection for a quantitative trait in Tribolium castenum. 2. Heritability and realized heritability

An experiment with the flour beetle Tribolium castaneum was carried out to study the long-term response to selection for pupal weight for 20 generatio ns. Three population sizes (10, 20 and 40 pairs of parents) and 3 proportio ns selected (10%, 20% and 30%) were considered along with a control for eac h population size. The experiment was replicated twice. Fullsib heritabilit y estimates for pupa weight did not follow any definite trend with regard t o population size or selection intensity. Pooled realized heritability esti mates were 0.52 in period-1(1 to 10 generations) and 0.35 in overall period (1 to 20 generations). At the end of the experiment, the selected and one control line were assayed for the residual genetic variability. There was a reduction of 54 to 66 % in the heritability estimates measured from offspr ing-parent regression at the end of the experiment, compared to those estim ated in the base population.