The scientific questions that interest us concern the mixture of bottom up and top down effects in food webs. In systems dominated by bottom up trophic interactions, the biomass of the chain lacks feedback from consumers. When top down forces are important, consumers rearrange biomasses in the trophic chain.

We study the ecology and evolution of marine cordgrasses, Spartina species that define and maintain the shoreline along broad expanses of temperate coasts the world over. These plants are valued as a barrier to the sea in native areas and in China and Europe where they have been cultivated. Our work is particularly concerned with non-native invasive cordgrasses in North America, Australia, Tasmania, and New Zealand, where Spartinas are seen as a bane both to ecology and to human uses of salt marshes and estuaries. We have concentrated upon hybridization of Spartina species. Four of the seven large-scale invasions of these plants around the globe have involved hybrids. Rapid evolution driven by selection of genotypes particularly adapted for invasive behavior could be the cause of observed high spread rates of hybrid cordgrass. The study of Spartina introductions is a rich mixture of social and basic sciences, with interaction of human values, ecology, and evolution.

We have been concerned with the ethics, policies, and social consequences of purposeful introductions of organisms for the control of pests. Our projects have involved the introduction of herbivorous and insectivorous insects and entomopathogenic nematodes.