Research

Our best guess is that about half of all multicellular species are insects that eat plants. It’s only a guess because most species are undocumented. Plant-eating insects are the good and the bad of biodiversity. 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 like recycling garbage and regulating the climate. 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.

Some sap-sucking bugs. Top left: Aphis coreopsidis; top right: Aphis sambuci; bottom left: Icerya purchasi, bottom right: Melanspis obscura.

Some sap-sucking bugs. Top left: Aphis coreopsidis; top right: Aphis sambuci; bottom left: Icerya purchasi, bottom right: Melanspis obscura.

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 a major driver of 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.