Is the heritability for courtship and mating speed in Drosophila (fruit fly) low?

Empirical studies indicate that heritable variation for courtship behaviour in Drosophila is often not detectable, whereas mating speed has a low heritability. These patterns have been used to make inferences about the association between mating behaviours and fitness. However, mating behaviours have been scored as single events, which can lead to underestimates of heritability values relevant to the lifetime fitness of an organism. To test this, repeated measurements on the same individuals were undertaken for time to courtship and mating in Drosophila melanogaster in both parental and offspring generations. Although there was no detectable heritable variation for both traits when parent-offspring comparisons were based on single events, heritabilities were significant and intermediate when the behaviour of each individual was averaged over several events. Estimates for mating behaviours relevant to the fitness of organisms are therefore much higher than indicated by single-event experiments.