Parental age and heritability of sternopleural chaeta number in Drosophila melanogaster.

Evidence is presented that the heritability of sternopleural chaeta number in Drosophila melanogaster is influenced by the age of the parents such that estimates based upon parents 14 days and older are significantly higher than those from 3-day-old parents. The increase is generally between 60 and 100 per cent when parents with mean ages of 3 days and 21 or 28 days are compared. The age-effect on h2 is more marked with age of mother, but there is a male effect when all comparisons are made between young mothers. The increase is found with estimates of h2 based both on offspring mid-parent regression and on half sib analyses, but may be more marked with the former. The increase in h2 is significantly less when females first mated when young are used than when females kept virgin until just prior to the test of heritability are used as old mothers. Some possible causes for these effects of parental age upon heritability and the expression of quantitative characters are discussed.