I am DeWitt Wallace Professor of Biology Emeritus at Macalester College. During my career, my research has included the study of insects, mammals, birds, and plants. Most of my recent research, writings, and presentations have focused on the ecology of introduced species and the field of invasion biology.

In 2000, using insights gained from succession ecology, Philip Grime, Ken Thompson, and I developed a new theory to explain community invasibility. Presented in the Journal of Ecology (Davis et al. 2000), the Fluctuating Resource Availability Theory of Invasibility predicts that a plant community will become more susceptible to invasion whenever there is an increase in the amount of unused resources. This theory rests on the simple assumption that an invading species must have access to available resources, e.g., light, nutrients, and water, and that a species will enjoy greater success in invading a community if it does not encounter intense competition for these resources from resident species. This paper has been cited more than 3700 times.

In 2009, Oxford University Press published Invasion Biology, a book I wrote on the subject of biological invasions and the history of the field of invasion biology. In 2011, Nature published an essay I and 18 coauthors wrote, titled Don’t Judge Species on Their Origins. This essay elicited vigorous discussion within the field of ecology, discussion which continues today.