Using Drosophila to study the evolution of herbivory and diet specialization

• Next-generation sequencing revolutionized the study of herbivorous insects.
• Comparative genomics and mapping studies identify candidate ‘herbivory’ genes.
• The Drosophila molecular toolbox can functionally validate candidate genes.
• Iterative use of these methods can systematically characterize ‘herbivory’ genes.

Herbivory evolved many times independently across the insect phylogeny, and its evolution is linked with increased rates of diversification. Plants present many barriers to potential herbivores, among them are the so-called secondary chemicals and other molecular defenses such as protease inhibitors that deter herbivores. To understand the mechanisms behind the emergence of herbivory and subsequent species radiations of insects driven largely by diet specialization, it is important to identify the molecular basis associated with these evolutionary transitions. However, most herbivore species lack the genomic information and genetic tools required to identify functionally important genes. The notable exception is the genus Drosophila in which herbivory evolved at least three times independently, and for which abundant genomic data are available. Furthermore, contained within the family Drosophilidae is Drosophila melanogaster, the first genetic model animal. Here, we provide a synthesis of the salient tools that the D. melanogaster system provides to identify functionally important genes required for herbivory and subsequent diet specialization across insects.