Trade-offs and coexistence in microbial microcosms

Trade-offs among the abilities of organisms to respond to different environmental factors are often assumed to play a major role in the coexistence of species. There has been extensive theoretical study of the role of such trade-offs in ecological communities but it has proven difficult to study such trade-offs experimentally. Microorganisms are ideal model systems with which to experimentally study the causes and consequences of ecological trade-offs. In model communities of E. coli B and T-type bacteriophage, a trade-off in E. coli between resistance to bacteriophage and competitive ability is often observed. This trade-off can allow the coexistence of different ecological types of E. coli. The magnitude of this trade-off affects, in predictable ways, the structure, dynamics and response to environmental change of these communities. Genetic factors, environmental factors, and gene-by-environment interactions determine the magnitude of this trade-off. Environmental control of the magnitude of trade-offs represents one avenue by which environmental change can alter community properties such as invasability, stability and coexistence. This revised version was published online in August 2006 with corrections to the Cover Date.