Our best guess is that about one third of all multicellular species are insects that eat plants. It’s only a guess because most species are undocumented. They eat our crops, disturb our natural areas, and spread plant diseases. But they also play essential roles in the ecosystems that provide us with valuable services, such as controlling weeds and feeding birds. Most plant-eating insect species are diet specialists, that is, they eat only one or a few similar plant species. But in every plant-eating insect community, there are a few species that eat more, and some of these can have extremely broad diets.
Our research addresses three major questions about plant-eating insect biodiversity: 1) What insect species eat plants? 2) Why are there so many of them? 3) Why are so many of them so picky about what they eat? The second two questions are intertwined, since we think that, in plant-eating insects, diet evolution has been wrapped up with speciation.
In the Hardy Lab, we address the first question by working on the systematics of sap-sucking bugs, in particular aphids and scale insects (Hemiptera: Sternorrnyncha: Aphidomorpha). We find and describe species, estimate phylogenetic relationships among species, and make tools to manage information about species.
To address the second two questions, we primarily use comparative phylogenetic methods, that is, statistical models to infer how the traits of species and their environments evolve and affect rates of speciation and extinction. But we are also beginning to use experimental evolution and comparative genomics approaches.