Quantitative wing variation in inbred and outbred lines of Drosophila melanogaster.

Variation of two wing morphology characters was studied in 11 X-chromosome substitution lines and three outbred lines of D. melanogaster, as a test of quantitative genetic predictions regarding variance components and heritabilities. As expected from inbreeding of the lines, between-lines components of phenotypic variance are statistically significant, while the significant within-line component is attributable to a maternal effect. Unusually low broad-sense heritabilities were observed in the inbred lines, and unusually low narrow-sense heritabilities were observed in the outbred lines. Low heritability estimates cannot be explained by insensitive measurement techniques, since the techniques were sufficiently sensitive to detect significant maternal effects. The most likely explanation for the low heritability estimates is the operation of natural selection on wing or correlated characters as stocks adapt to the laboratory environment.