The relationships between developmental components and correlation structure are explored for 17 head and thorax traits of Drosophila melanogaster. A developmental basis for the patterns of genetic and phenotypic correlation is described and related to information on the growth of various imaginal discs. In general, correlations between traits are positive, reflecting the similarity of cell doubling times of the various imaginal discs and the overlapping times of their growth during the larval instars. Positive correlations between traits provide a mechanism that can constrain radical evolutionary divergence from the fundamental body plan recognized as a fly. Phenotypic and genetic correlation structures are generally consistent with a hypothesis that traits derived from the same imaginal disc are more highly correlated than those derived from different discs. This structure is consistent with observed patterns of morphological divergence within the order Diptera. Furthermore, higher within-disc correlations provide a mechanism for evolutionary fine-tuning of the phenotype of a population of organisms to variable environmental conditions.
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Cowley et al. (1990) studied this question.