Biography of David Tilman

D avid Tilman describes himself as both a theoretical and an experimental ecologist. Currently the McKnight Presidential Chair in Ecology and Regents Professor at the University of Minnesota (St. Paul), Tilman has spent his career developing theories of biodiversity and species composition that he has tested in carefully designed and controlled experiments. His work on resource competition in both algal and grassland ecosystems has helped shape ecology into a more predictive and quantitative science. For this and numerous other contributions, Tilman was elected to the National Academy of Sciences in 2002. In his Inaugural Article, featured in this issue of PNAS (1), Tilman presents a new theory of species diversity and abundance within ecosystems. The theory was inspired, in part, by data he gathered over the past two decades at the Cedar Creek Natural History Area (Bethel, MN), where he currently serves as director. Through his new stochastic niche theory, Tilman offers an explanation for the patterns seen during the assembly of species into ecosystems, including what controls the number of species and their abundances, and why some ecosystems are more readily invaded by exotic species than others. The article suggests that stochastic niche theory offers a resolution to the controversy between whether it is ‘‘neutral’’ or ‘‘niche’’ processes that determine the diversity and composition of ecosystems.