Quantitative morphological variation in the developing Drosophila wing
Quantitative variation in morphology is pervasive in all species and is the basis for the evolution of differences among species. The developmental causes of such variation are a relatively neglected research topic. Quantitative comparisons of variation arising at different developmental stages with the variation in the final structure enable us to determine when variation arises, and to generate hypotheses about the causes of that variation. We measured shape and size variation in the wing of Drosophila melanogaster at three developmental stages: late third instar, post-pupariation and in the adult fly. Flies of a wild-type and two mutants (shf and ds) with effects on the adult wing shape and size were studied. Despite experimental noise related to the difficulty of comparing developing structures, we found consistent differences in wing shape and size at each developmental stage between genotypes. In addition we provide linear rules allowing to link late disc morphology with early wings. Our approach provides a framework to analyze quantitative morphological variation in the developing fly wing. This framework should help to characterize the natural variation of the larval and pupal wing shape, and to measure the contribution of the processes occurring during these developmental stages to the natural variation in adult wing morphology.