COMPARISON OF PREDICTED AND SIMULATED RESPONSES TO MASS SELECTION IN A DIPLOID, CROSS-FERTILIZED SPECIES

Abstract

Computer simulation was used to study the relative effectiveness of mass selection under additive and complete dominance genetic models and the accuracy of the mathematical formulae for predicting mean response and variance of response to selection. Four selection regimes were simulated over 30 cycles and embodied a high (5%) or a low (25%) selection intensity and a high (0.6) or a low (0.2) heritability. Mass selection was most effective under the high selection intensity, high heritability regime and least effective under the low selection intensity, low heritability regime. The greatest gains occurred in the early cycles of mass selection and were higher in the complete dominance model than in the additive model, but the amount of gain per cycle decreased at a faster rate under the complete dominance model. Predicted gain under the additive model was in good agreement with simulated gain, but, under the complete dominance model, predicted gain overestimated the simulated gain, probably due to the build-up of genetic disequilibrium during selection. Selection responses deviated more from the mean response under the high selection intensity, low heritability regime than under the other regimes. The predicted variance of response to selection appeared to be in good agreement with the simulated variance in every selection regime.