The primary goal of this research project is to identify how changes in DNA sequence and organization produce diversity in the shape and structure of body parts. The head shape of stalk-eyed flies will be used as a model system for investigating this issue. These flies have undergone extreme modification of the head into long stalks with the eyes located at the ends of these stalks. There is tremendous variation within and between species in terms of eyestalk size and shape. This project will examine variation in stalk-eyed fly DNA that is associated with eye-stalk variation as a means for identifying the genetic basis of this bizarre trait. The primary focus will be on the regulatory regions of genes which control when and where genes are turned on and off within the body. DNA variation will be examined at three levels: among species to identify genes evolving in concert with eye-stalks, within two species that differ dramatically in eye-stalk size and between lines of flies from one species that have been artificially selected for large and small eye-stalks. The results from this project will enhance our understanding of how and where variation accumulates in the genome and how this molecular variation produces phenotypic diversity. This research will have implications for numerous biomedical fields interested in alternative phenotypes and the molecular processes that produce them. [unreadable] [unreadable]