Fluctuating asymmetry does not increase with moderate inbreeding in Drosophila melanogaster.

Fluctuating asymmetry, the unsigned difference between character values on the left and right sides of an individual, is often thought to be highly correlated with the heterozygosity of individuals or populations. A large sample of Drosophila melanogaster individuals with an inbreeding coefficient of F = 0.25 was derived from a laboratory population and compared to a sample of outbred individuals for the fluctuating asymmetry of sternopleural bristle number. Inbred flies were not more asymmetric than outbred flies. There was no evidence for heritability of fluctuating asymmetry, as measured by variance among full-sib lines. Fluctuating asymmetry may not be a reliable measure of the degree of inbreeding at the relatively low levels found in most animal populations and should be used with caution in the management of endangered species.