An Investigation into Patterns of Scaling Among Morphological Traits

Proper scaling of morphological traits to body size is necessary for ecological function. Individuals with better nutrition grow larger body sizes and traits, whereas individuals with poor nutrition develop smaller body sizes and traits. However, morphological scaling relationships may differ among traits. Fly wing size scales approximately 1:1 with body size, whereas traits such as beetle horns have a larger trait to body size ratio and insect genitalia has a smaller trait to body size ratio. Changes in the slopes of such scaling relationships result in morphological evolution, but the role of development in the expression of scaling relationships and how variations in development will influence the changes in scaling are unknown. Individual Drosophila melanogaster from isogenic lines were subjected to different diets in the larvae stage to produce the complete size range for each genotype. The wing and body size of these individuals were measured and used to fit genotype-specific scaling relationships. We will investigate the scaling of other morphological traits in the lineages that exhibit the steepest and most shallow slopes for wing: body size scaling, to determine if scaling across traits is correlated within a genotype. Such correlations may suggest that the same alleles regulate scaling for multiple traits, suggesting a restriction on the independent evolution of morphological scaling relationships.