The evolution of body size and shape: the evolutionary and developmental genetics approach.

Genetically based body size and shape differences among Drosophila populations from different climatic areas or after natural selection for temperature in the lab are well known. Usually, bigger individuals show larger structures with respect to the smaller ones, but the relationships between adult structures and total body size can significantly vary among populations and/or species. Development in multicellular animals is a process that involves both tight control and flexibility. Little is known about developmental mechanisms that generate allometry and about their relative evolutionary importance. In Drosophila, the discovery that during development cell division within imaginal discs uses borders of clonal restriction as references offered the opportunity to develop models of how cells, through proliferation, generate morphological space of finite size and shape and to integrate quantitative studies in the development. Here we propose methods for combining developmental and quantitative studies to investigate the relative importance of integration versus modularity in development and evolution.