- Evolution and ecology of plant-insect interactions, with emphasis on pollination ecology and insect herbivory. Long-term (macroevolutionary) perspectives on plant-insect (co-)evolution, based on molecular-phylogenetic studies of the evolution of chemical and floral traits and ecological relationships.
- Quantitative genetics and development of floral traits involved in attracting, rewarding, and manipulating pollinators; correlated evolution, constraint, and evolvability of floral traits.
- Community ecology, including biotic interactions and effects of local variation in microclimate on the composition and function of plant and insect communities; latitudinal patterns in beta-diversity (species turnover across microhabitats).
- Biogeography: molecular phylogeography and ecology of Beringian plants and insects.
- Evolution of plant mating systems and correlated floral traits, with current emphasis on Collinsia and Tonella(Plantaginaceae).
- Tropical conservation biology, biological consequences of forest fragmentation.
PhD and MSc studies at the University of California, Davis. Previous professorships at Norwegian University of Science & Technology (Trondheim) and University of Alaska Fairbanks.