Dr. Simpson's laboratory is engaged in an array of studies that deal with the phylogeny and biogeography of various angiosperm groups. Taxonomic groups range from monocots to the Asteraceae. Most biogeographic work is directed toward explaining patterns seen in the American Southwest, Mexico, and Central and South America. Methodologies for uncovering evolutionary histories include the use of cpDNA restriction fragment pattern analysis and gene sequencing as well as traditional techniques. The relationships between native solitary bees and their New World hosts are also of interest. Many of these studies have involved the interactions between anthophorid bees and plants with oil-secreting flowers. Other studies concentrate on reward production, foraging behavior, and nest provisioning by native bees.