Research in my lab is focused on understanding how biological interactions and environmental change affect plant evolution. We use a variety of organisms (including Zea , Clarkia , Arabidopsis , Medicago and Sinorhizobium ) and a variety of molecular and organismal approaches (including molecular population genetics, greenhouse and field studies, and quantitative genetics). I am involved currently in a variety of projects investigating i) the molecular evolution of plant immune system genes, ii) evolutionary responses to elevated CO 2 concentrations and other environmental changes, and iii) the ecological and evolutionary limits to species range expansion. I also remain interested in understanding the ecology and evolution of plant resistance and tolerance to herbivores and pathogens.