Predicted rates of inbreeding with additive maternal effects

Maternal effects play an important role in fitness and other aspects of individual performance in many species, particularly mammalian, yet their impact on genetic variation within species and its rate of loss during selection has been neglected. In this paper we extend the theory of expected long-term genetic contributions to include maternal effects, and tested the accuracy of predicted rates of inbreeding for populations under mass selection by comparison with simulations. The model includes selective advantages of direct and maternal additive genetic effects, and also the selective advantage of a common maternal environmental effect. The population structures investigated had a fixed number of dams per sire and fixed family size. Most prediction errors of the rate of inbreeding (deltaF) were less than 8% of the simulated means and were lower in magnitude than the prediction errors of genetic gain (deltaG). The predictions of deltaG from contributions equalled previously published predictions. A variation in maternal genetic effects resulted in a much larger deltaF than for an equally sized variation in common maternal environmental effects. For a fixed genetic gain, deltaF increased as the maternal heritability increased. The influence of family size, mating ratio and age structure on deltaF was greater with maternal effects than with only direct genetic effects included. In conclusion, maternal effects can be a very important aspect to consider when predicting deltaF in populations under selection, and the developed methodology gives good predictions.