Variation in morphological traits of Drosophila melanogaster (fruit fly) under nutritional stress.

The effect of nutritional stress on phenotypical and genetic variation was examined for five morphological traits (thorax length, wing length, sternopleural chaeta number, abdominal chaeta number and arista branch number) in 30 isofemale lines of Drosophila melanogaster. Phenotypical variation of all traits except sternopleural chaeta number and fluctuating asymmetry of all bilateral traits were significantly higher in flies reared under poor feeding conditions. Estimates of isofemale line heritability (coefficients of intraclass correlation) did not show a consistent pattern among traits. However, additive genetic variance was generally higher in poor feeding conditions in all traits except sternopleural chaeta number, although these differences were not statistically significant. Similarly, estimates of evolvability were higher under nutritional stress for all traits except sternopleural chaeta number. These results suggest that nutritional stress increases the expression of genetic variation for some morphological traits in Drosophila and, in this respect, is similar to the effects of temperature stress studied previously.